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- May 21, 2012
- 03:32 PM
- 38 views
Communal mining bees
A few years ago, a crack in the concrete path at the front of our house became busy with bees coming in and out. We assumed they were honeybees that had settled their hive there, but on closer inspection they turned out to be mining bees instead. Their cleptoparasite bees, Nomada, hung around the nest entrance awaiting an opportunity to get in and lay their eggs. There are many similar species of Andrena mining bees in the UK and several of them looked very similar to mine so I finally gave up with obtaining an ID and I didn't find much more about my front path bee. The bees are back again in the same spot, and a couple of days ago, thanks to tweep @DayMoonRoseDawn I finally knew the identity of these curious bees: they are Andrena carantonica, a large, furry mining bee. Although mining bees are solitary, a handful of species in the UK often nest communally. Communal bees have a simple form of social structure: they share a nest, but individual females will build their own cells, lay eggs and provision their own offspring: they do not have the complex social organisation with workers and division of labour of honeybees. Nesting aggregations of A. carantonica consist of hundreds of females (up to 600) females using the same nest entrance. In my street, cracks on concrete in front garden paths are favoured. Adults emerge in April, with the smaller males doing so just before females and awaiting them inside the nest. In a series of study on this species by Robert Paxton and collaborators reveaed fascinating details of the social structure of this species. In one of these studies they installed nets on nest entrances to be able to capture recently emerged bees: 75% of females were already inseminated when they left the nest for the first time, indicating that copulation happens most of the time inside the communal nests. Although the females in the nest are not highly related, there is a large amount of inbreeding in this species: genetic analysis suggests that 44% of females mate with their full brothers. Emerging females are much more numerous in a given nest (about 1 male to 3 females), although, as Rose Dawn pointed out, it is likely that many males never leave the nest and die inside after having mated, so emergence nets do not capture them. Females must by necessity swap nests after emergence so that the relatedness levels is still low within a given nest, and the bees show a high degree of tolerance to conspecifics, regardless of their nest of origin. If a high level of relatedness is not responsible for the evolution of communality, why do these bees nest communally? A potential benefit is improved nest defence. There are always bees going in or out, and in my own observations, a few bees often sit by the nest entrance (like as in the photo at the top), therefore opportunities for parasitism by cleptoparasites might be reduced. There are still many questions to answer, which probably will have to await to observations being carried out inside nests, but the study of these and other communal species might offer clues as to how and why complex social systems like those of honeybees evolved.A male Andrena carantonica near the nest entranceFemale Andrena carantonicaA cleptoparasite bee Nomada flava by mining bee nest entrance.Thanks to Rose Dawn for providing an ID and sharing lots of information on this bee, including results from her own researchMore informationPaxton, R., Thoren, P., Tengo, J., Estoup, A., & Pamilo, P. (1996). Mating structure and nestmate relatedness in a communal bee, Andrena jacobi (Hymenoptera, Andrenidae), using microsatellites Molecular Ecology, 5 (4), 511-519 DOI: 10.1046/j.1365-294X.1996.00117.xPAXTON, R., THOREN, P.A., & GYLLENSTRAND, N. (2000). Microsatellite DNA analysis reveals low diploid male production in a communal bee with inbreeding Biological Journal of the Linnean Society, 69 (4), 483-502 DOI: 10.1006/bijl.1999.0371... Read more »
Paxton, R., Thoren, P., Tengo, J., Estoup, A., & Pamilo, P. (1996) Mating structure and nestmate relatedness in a communal bee, Andrena jacobi (Hymenoptera, Andrenidae), using microsatellites. Molecular Ecology, 5(4), 511-519. DOI: 10.1046/j.1365-294X.1996.00117.x
PAXTON, R., THOREN, P.A., & GYLLENSTRAND, N. (2000) Microsatellite DNA analysis reveals low diploid male production in a communal bee with inbreeding. Biological Journal of the Linnean Society, 69(4), 483-502. DOI: 10.1006/bijl.1999.0371
- March 30, 2012
- 12:36 PM
- 139 views
Why are some hoverflies poor mimics?
Merodon equestris, the Narcissus fly, a bumblebee mimicEristalis tenax, a dronefly (top left) and honeybeeVolucella zonaria, a large and colourful hoverfly that is an excellent mimic of the european hornet Vespa crabroHelophilus, a wasp mimic Sericomia silentis, a wasp mimicThe photos above illustrate that hoverflies are amongst the best examples of mimicry. Although harmless, their colours, patterns, level of hairiness, and detailed morphological and behavioural features often matches species of bees, bumblebees and wasps, making them such wonderful impostors that they fool peopleinto thinking they really are stinging bees or wasps. At close range, anybody can learn to tell mimics and models apart (the shape and size of the antenna is a giveaway). But thefantastic mimicry of hoverflies is shown by the repeated identification failures ofnatural history photographers, and even specialised editors (a book cover on bees featuring a hoverfly). These are evident when you have a look at many natural history photography websites. As an example I googled "wasp flower" and the first hit was a hoverfly.The selective pressure for mimicry is predation. Manybirds are consummate fly predators, but they will avoid bees and wasps. Although birds could benefit nutritionally from preying upon these succulent, soft flies there is a heavy cost to pay if they get it wrong: a painful and possibly debilitating sting. Given this, shouldn’t natural selection perfect mimicry? Why arethere some hoverflies that only have a vague resemblance to bees and wasps? Here is an example:Syritta pipiens, an example of a poor mimic There had beenmany hypotheses put forward to explain why there are poor mimics:'Eye of the beholder': Imperfect mimics are only imperfect to the human eye, they are really much better mimics to bird eyes. The poor resemblance would be a reflection of our own perception bias.'Multimodel' Maybe mimics could be safer when imitating roughly several models.'Kin selection' Flies that are abundant might be surrounded by relatives, and kin selection might have selected for these imperfect mimics.'Trade offs' mimetic perfection cound be trading off with camouflage ability, or thermoregulation.'Constraints' mimicry could be limited by developmental or phylogenetic constraints.'Relaxed selection': small hoverflies – which are less profitable to eat – could have lower predation even if they are poor mimics, which will mean that natural selection for improved mimicry will be weaker.Heather Penney and co-authors tested these hypotheses using a large set of European hoverfly species. They obtained morphological data and human volunteer rankings of mimicry fidelity to bee, bumblebee and wasp models and phylogenetic data to test these hypotheses.First, they carried out a detailed morphological analysis on a large set of hoverlfy species which shows that human perception of mimicry fidelity indeed corresponds to objective assessments of similarity between mimic and model based on their morphological analysis. This rules out the 'eye of the beholder hypothesis" and also the 'multimodel' as poor mimics did not fall in between different potential models.They also performed a meta-analysis showing that poor mimics were not more abundant than accurate mimics and therefore rules out the importance of kin selection in the evolution of imperfect mimicry.The constraints hypothesis, they did not explicitly test even when they had phylogenetic data to evaluate the importance of phylogeny as a constraint.The core result of the paper was that the degree of fidelity to the model is strongly correlated with hoverfly body size even when correcting for phylogenetic relationships, as shown in their figure:Relationship between an estimate of body size and human ratings of mimetic fidelity (fHR). Lines show the fitted linear regressions. Filled triangles, wasp mimics; open triangles, bee mimics; filled circle, the non-mimetic syrphid Cheilosia vernalis (from Penney et al 2012)As the benefit of predating a hoverfly (a meal for the bird) is directly related to the size of the fly, while the cost of error should be constant, the higher risk of predation when the hoverfly is large imposes a higher selective pressure to be a good mimic. Therefore, a hoverfly doesn’t need to be a good mimic if it is small, as the benefit of eating a small fly for a bird is too insignificant to risk the potential cost, therefore resulting in a lower predation pressure for small hoverflies. Birds will err on the side of caution and avoid even the poor mimics when they are small. The other way round: Large hoverflies provide a bigger benefit, so the predator might risk being stung and therefore they have been selected for more precise mimicry. Although the results are solid and the hypothesis makes intuitive sense, I found two problems with their design: (1) the limited choice of models and (2) the geographically biased choice of some models, both of them resulting in an underestimation of the degree of mimicry of some hoverflies.First, not all potential models or even model types were available and this will create an alternative explanation for the evolution of "poor" mimicry, if you can't compare the mimic with its model, they it will by necessity result in a poor mimic. There are hundreds of European species of bees, wasps and bumblebees with a broad range of colours and patterns, but they only used ten. Syritta pipiens, the little hoverfly shown above was rated as a poor mimic in their study, but who says it doesn't mimic a small solitary wasp or bee not included as a model?In addition, of the three bumblebee species they included two were American bumblebees (B. affinis and B. impatiens), which seemed strange given that their hoverfly sample was European. A single European bumblebee, B. lucorum was included. Given that bumblebees differ extensively in coat colou... Read more »
Penney, H., Hassall, C., Skevington, J., Abbott, K., & Sherratt, T. (2012) A comparative analysis of the evolution of imperfect mimicry. Nature, 483(7390), 461-464. DOI: 10.1038/nature10961
- March 26, 2012
- 04:47 PM
- 191 views
Do spiders find ladybirds distasteful?
I witnessed a curious interaction today. A 7 spot ladybird was walking up a wall, when a sudden movement caught my eye. It was a large spider, a female Amaurobius similis that had dashed out of her burrow in a hole in the wall, probably alerted by the pull of one of the silk threads that radiate from her burrow. She had caught the ladybird by one leg. The ladybird struggled to free itself, but she need not fight much. After a few moments, the spider released her grip, turned round and retreated into her burrow. The spider obviously had assessed the ladybird and regarded it not suitable for a meal. I doubt it was due to the ladybird size or strength, as Amaurobius are powerful spiders, able to subdue large flying insects such as droneflies and honeybees. The other possibility is that the spider has tasted the alkaloid rich liquid that constitutes ladybirds chemical defence mechanism and that is released from their leg joints when alarmed (the 'blood reflex'). I have previously seen dead ladybirds wrapped on silk caught on the webs of two spider species (garden spiders Araneus diadematus and the false widow Steatoda bipunctata). Indeed, field surveys and experiments carried out by John Sloggett showed that A. diadematus does trap and consume ladybirds, and is apparently immune to the toxic effects of ladybird's chemical defences. In contrast, other spider species do seem to find ladybirds distasteful, so this is a strong possibility for Amaurobius.Another view of the interaction, not as sharp, but it shows clearly how the spider's chelicerae are pulling and lifting the ladybird's front right leg.For other spiders, however, ladybirds are not even considered a food item. Take this little wolf spider, enjoying the company of the 7 spot ladybird a few days ago. Both individuals were sunbathing next to each other most of the morning. The spider popped in and out, paying no attention whatsoever to the ladybird.More informationSloggett, J. (2010). Predation of ladybird beetles by the orb-web spider Araneus diadematus BioControl, 55 (5), 631-638 DOI: 10.1007/s10526-010-9291-0... Read more »
Sloggett, J. (2010) Predation of ladybird beetles by the orb-web spider Araneus diadematus. BioControl, 55(5), 631-638. DOI: 10.1007/s10526-010-9291-0
- March 9, 2012
- 05:04 PM
- 175 views
Silent aliens
Have a look at these:Harlequin LadybirdLily BeetleWestern Conifer BugThey are invasive insect species in the UK. They are also so bright, or large, that they are hard to miss. You'll come across them even if you don't look. Many, many other alien invaders are harder to notice, they arrived, and before anybody other than specialist taxonomists noticed, they have spread across sizeable portions of the country. Many such silent invasions involve invertebrates that are small and or hard to identify. Clutches of snail eggs in the soil of pot plants, or dormant adults in cracks in stones or other cargo are often sent as inadvertent stowaways across countries thousands of miles away. They arrive in the destination, thrive and begin a quiet invasion. As many snails are tiny, and to the untrained eye they look identical to other snails, they are transported about very often. A sizeable fraction of the snails species of Central Europe is now thought to be of alien origin (about 15%), most of Mediterranean origin and the trend is of a recent increase, aided by increasing temperatures and commerce. In some extreme cases the ability of the snails to disperse is extremely limited, or their requirements for specific substrata so high that they scarcely move after introductions. Such is the case of Papillaria papillaris, a minute snail native of Italy, Sicily and Malta. These snails were likely to have been introduced in the UK in the 18th century with Italian ornaments or stonework, then prized by affluent stately home owners. Just two populations (in Brownsea Island Castle and Cliveden House) have been found so far. Amazingly, they have barely moved a few meters in this time, although they form self-sustaining colonies. Likewise, in Spain, this snail is restricted to walls and ruins from the Roman period, two millennia living practically where they were placed! Of course, there are many examples of the other extreme of the spectrum. Species that quickly spread on arrival, or after a lag period. An example is the Girdled Snail, Hygromia cinctella, a snail of Mediterranean origin which now is rapidly expanding in the UK. It was first noticed in the South in 1950, and it has now reached Glasgow, that is fast - for a snail. There have been suggestions that the snail might travel as stowaways in cars! Although this might seem outrageous, snails' habit of climbing up vertical surfaces and attaching itself firmly for aestivation or overwintering might facilitate this and it has been documented that this behaviour increases transport by cars. The girdled snail is 1 cm across and triangular when looked at from the side, with a pronounced keel that sports a pale line. At a distance looks like a juvenile garden snail. My daughter, however, noticed this snail on the pavement in my street a few days ago and it was necessary to rescue it from being crushed by passers by. I only noticed it wasn't a garden snail when I picked it up, after it had retreated into its shell. I will keep a close eye and see if it has already arrived in my garden.Side view showing the keel and pale edge.Underside showing the lack of umbilicusMore informationBurçin Aşkım Gümüş and Henk K. Mienis (2010) Records of Papillifera papillaris affinis in continental Spain and their connection with walls and ruins from the Roman period. The Archaeo+Malacology Group Newsletter, 18: 1-4. here.Janet Ridout-Sharpe (2010) Papillifera papillaris: a second colony is discovered in England. The Archaeo+Malacology Group Newsletter, 18: 1-6. here.Alena Peltanova, Adam Petrusek, Petr Kment, Lucie Jurˇicˇkova (2011). A fast snail’s pace: colonization of Central Europe by Mediterranean gastropods Biological Invasions : 10.1007/s10530-011-0121... Read more »
Alena Peltanova, Adam Petrusek, Petr Kment, Lucie Jurˇicˇkova. (2011) A fast snail’s pace: colonization of Central Europe by Mediterranean gastropods. Biological Invasions. info:/10.1007/s10530-011-0121
- March 3, 2012
- 03:50 PM
- 154 views
The bird with the silvery eyes
In his most amusing book King Solomon's Ring, Konrad Lorenz described his experiences rearing a veritable menagerie of different animals including jewel cichlids, water shrews, a raven, cockatoos geese and ducks. His intention was to develop an intimate relationship with them and understand their behaviour and communication. He reared the birds himself then set them free. This allowed him to have very tame animals that could be observed from close quarters. The longest chapter is devoted to his colony of Jackdaws (Coloeus monedula), which he started by hand-rearing more than a dozen of them. He ringed his Jackdaws with colour and metallic rings and named them accordingly to their ring colours. This chapter is a vivid account of Jackdaw behaviour. Lorenz was of the opinion that you had to get under the animal's skin to understand their actions, and his fascinating account shows that he got very close to feeling like a Jackdaw and he was definitely treated by one with a male that adopted him as his partner and insisted in feeding him chewed worms.Flying togetherJackdaws are very sociable corvids, they like to fly in tight flocks. The members flock feed together and breed together in loose colonies in natural holes in cliffs and old trees and in buildings commonly using chimney pots. He described the "kia" call as equivalent to "fly away with me" and a longer version he learned to distinguish "kiaw" as "fly back home with me". His first jackdaw, Jock found dark birds flying away from him irresistible, and would often pursue a Hooded Crow away in his walks with Lorenz. Adults use this instinct to entice young to fly with them and will keep a close eye "looking over their shoulders" as they do so, to make sure the young can follow. Lorenz noticed how adults adjusted their flight and made it slower when fledglings were flying with them, making it easier for the young to follow.The rattling reactionOne of the most surprising discoveries made by Lorenz was the instinctive basis of the rattling reaction and how . He found by chance - by taking his black swimming trunks from his pocket - that a dark floppy object held by something was a very strong signal that started a furious attack. His tame jackdaw attacked his hand drawing blood. The pecking was accompanied by loud rattling calls. In other occasions - such as when he intended to ring the young jackdaws in his colony, he observed that holding the feathered young will draws the members of the flock together into a rattling reaction. This presumably has the function that a predator that catches a jackdaw receives such a severe punishment. The memory of the offender is imprinted into all the members of the flock participating in the rattling reaction and will persist for years and form the basis of local traditions that will be passed down generations. As the rattling reaction was elicited when Lorenz held feathered young for ringing, he decided to dress up with the only outfit he had at hand - a devil costume - and climb onto his roof to ring the young jackdaws. A sight that shocked some of the people of his village one day.A pecking orderThe jackdaw flock has a precise stable hierarchy. There is a pecking order in which "very high caste jackdaws are most condescending to those of lowest degree and consider them merely as the dust between their feet" according to Lorenz. Males, which are larger than females are higher in the rank. High ranking jackdaws always takes the weaker side when intervening on disputes, which helps maintaining the cohesiveness of the colony. The way Jackdaws assert their dominance is by raising the neck pale feathers.A pair of jackdaws basking in the early morning sunLifelong partnersJackdaws are socially monogamous and pair for life. Pairs form on the individuals' first spring, although they are unlikely to breed until their second spring due to a shortage of nesting sites. The partners in a jackdaw pair are together all year round and support each other loyaly in any dispute. The rank of a new female partner automatically rises correspondingly in the female's rank order, a refinement of Lorenz discoveries explained in the later monograph on Jackdaws by A Roell. Lorenz said he was surprised how quickly all jackdaws in the colony knew of the rise in rank of the new partner of the recently arrived alpha male. But not only that, the female also knew that now she stood over everybody else! The male will show the female a nest site by calling her with "zink" calls. The bond between the pair is shown by allopreening, usually by the female which will preen her partner's neck, particularly his silvery feathers. The female also will beg for food and the male will courtship feed her as he will in time feed the young. Both male and female share the building and defence of the nest and the rearing of the young but only the female incubates. During incubation, the male will feed the female.The few pairs of local Jackdaws now sitting on their nests remind me of Lorenz entertaining book.More informationKonrad Lorenz (1954). King Solomon's ring: new light on animal ways Methuen, London Other: 0415267471Röell, A. (1978). Social Behaviour of the Jackdaw, Corvus monedula, in Relation To Its Niche Behaviour, 64 (1), 1-122 DOI: 10.1163/156853978X00459... Read more »
Röell, A. (1978) Social Behaviour of the Jackdaw, Corvus Monedula, in Relation To Its Niche. Behaviour, 64(1), 1-122. DOI: 10.1163/156853978X00459
- February 16, 2012
- 04:04 PM
- 167 views
Builder Wren and counting hens
Wrens start singing early. They have been doing it occasionally since the first days of January, their powerful quick song cheering up the dark winter days. Today they seem to have gone for it on earnest: I heard four different males singing on my way to work. They have lots to do and there is so little, precious time. They have to start building their nests before females are ready to lay. Yes, I said nests, not just one, but many, lots, as many as he can possible make before the females start visiting. And also, I said females, as wrens are polygynous, with one male mating with between one to nine females per season. Each spring, male Wrens, Troglodytes troglodytes, build several nests in their territory in quick succession. They are called "cock nests" and are spherical, with a side entrance, placed in suitable locations and offer the structure of the finished nest (the female will line it with hair and feathers). It takes between half a day to five days to make a nest. Although Wren's songs are incredible powerful for their minute size it is the nests the females will judge before settling for a male, in particular, the number of nests. The male will display to entice the female to each vacant nest, singing and excitedly guiding her to the nests, to advertise what an accomplished builder he is. The more empty nests a female is shown the better. The next graph shows the positive relationship between the number of nests built by a male and the number of females making breeding attempts - and therefore the number of fledglings that the male will sire.(from Evans and Burn, 1996) Males vary in their ability to make nests - or in their ability to defend a territory where the nests can be built. Age makes a difference, with older males better at making nests. Habitat structure is also important, with denser vegetation indicating a better territory, where nests are less likely to be predated. But the most important explanatory factor is male condition: heavier males at the beginning of the season will be able to make more nests, so the number of nests is a measure of male quality. Females benefit from mating with males demonstrating their good condition, so it pays them to carry out a nest count before settling for a male. Experimental manipulating of number of nests present on each male's territory carried out by Mathew Evans and Joe Burn showed that the actual number of nests is the mate-choice cue that the female uses to assess male quality. The making of multiple nest by the male wren as an ornament, an extended phenotype result of the same factor than the tail of the peacock, a signal of quality selected by sexual selection.ReferencesEvans, M. (1997). Nest building signals male condition rather than age in wrens Animal Behaviour, 53 (4), 749-755 DOI: 10.1006/anbe.1996.0311Evans, M., & Burn, J. (1996). An experimental analysis of mate choice in the wren: a monomorphic, polygynous passerine Behavioral Ecology, 7 (1), 101-108 DOI: 10.1093/beheco/7.1.101... Read more »
Evans, M. (1997) Nest building signals male condition rather than age in wrens. Animal Behaviour, 53(4), 749-755. DOI: 10.1006/anbe.1996.0311
Evans, M., & Burn, J. (1996) An experimental analysis of mate choice in the wren: a monomorphic, polygynous passerine. Behavioral Ecology, 7(1), 101-108. DOI: 10.1093/beheco/7.1.101
- February 11, 2012
- 05:24 AM
- 160 views
The impact of Harlequins on native ladybird fauna
Harlequin ladybirds (Harmonia axyridis) are one of the most obvious invasive species in the UK. They are large and voracious and there was much speculation on their potential negative impact on the native ladybird fauna, given that they are regular predators of other ladybirds, especially during the vulnerable larval and pupal stages. An open access paper published today by Helen Roy and collaborators uses a powerful combination of citizen science (in the form of Ladybird online surveys) and systematic surveys to address directly the impact of Harlequins on the distribution and abundance of eight once common and widespread ladybird species in the UK, Belgium and Switzerland. Their statistical analysis on geographic distribution addressed the impact of the arrival of Harlequins on each species for well-sampled km2. The results are very clear, but also worrisome: the arrival of Harlequins had a negative impact on the distribution of 5 out of 8 species in Belgium and on 7 out of 8 species in Britain. The effect was large and the affected species have now contracted in range. The effects were striking for the small 2 spot ladybird, Adalia bipunctata, - a tree specialist - , which declined a 30% in Belgium and 44% in Britain in the 5 years following the Harlequin arrival. Although some of these species that were already declining, the presence of the Harlequin intensified the rate of decline.Figure 1 Effects of Harlequin arrival on the distribution of eight native ladybirds based on predictions for an average 1-km2. Prediction is based on the fixed effects of the models and ignores random variation in occupancy among specific 1-km2. Absent assumes the 1-km2 is not colonized by the Harlequin, and present assumes the 1-km2 was colonized in 2001 (Belgium) or 2004 (Britain) by the Harlequin. Note that our predictions are shown in the measurement scale (probability of occupancy), rather than the modelled scale (logit). (from Roy et al 2012) The systematic surveys of ladybird abundance in the tree habitats favoured by Harlequins supported these results and showed that the numbers of all native ladybirds decreased since their arrival, especially markedly in the UK. The only species relatively immune to their invasion is the 7 spot ladybird, a large species that favours herbaceous vegetation and is less likely to overlap in niche with Harlequins. Local or regional extintions of some tree specialist species seem like a certainty, and the impact this will have on agricultural systems is hard to predict. The following gallery is a celebration of the diversity of native European ladybirds, with the species used in the study.Pine ladybird, Exochomus quadripustulatus Orange Ladybird, Halyzia sedecimguttataA winter aggregation of 7 spot ladybirds, Coccinella septempunctataCream Spotted Ladybird Calvia quatuordecimguttata 10 spot ladybird, Adalia decempunctata2 spot ladybird, Adalia bipunctata14 spot ladybird, Propylea quattuordecimpunctata22 spot ladybird Psyllobora vigintiduopunctata More informationRoy, H., Adriaens, T., Isaac, N., Kenis, M., Onkelinx, T., Martin, G., Brown, P., Hautier, L., Poland, R., Roy, D., Comont, R., Eschen, R., Frost, R., Zindel, R., Van Vlaenderen, J., Nedvěd, O., Ravn, H., Grégoire, J., de Biseau, J., &; Maes, D. (2012). Invasive alien predator causes rapid declines of native European ladybirds Diversity and Distributions DOI: 10.1111/j.1472-4642.2012.00883.x... Read more »
Roy, H., Adriaens, T., Isaac, N., Kenis, M., Onkelinx, T., Martin, G., Brown, P., Hautier, L., Poland, R., Roy, D.... (2012) Invasive alien predator causes rapid declines of native European ladybirds. Diversity and Distributions. DOI: 10.1111/j.1472-4642.2012.00883.x
Gardiner MM, O'Neal ME, & Landis DA. (2011) Intraguild predation and native lady beetle decline. PloS one, 6(9). PMID: 21931606
Gagnon AÈ, Heimpel GE, & Brodeur J. (2011) The ubiquity of intraguild predation among predatory arthropods. PloS one, 6(11). PMID: 22132211
- February 10, 2012
- 05:53 PM
- 171 views
Bold as a coot
Coots are the odd ones out in their family. Unlike other rails, they are bold, noisy and aggressive birds. Instead of searching for cover, they are all out, even their nests are usually placed in the open water and they are as prominent that you cannot miss them. Their squabbles amongst themselves and with other birds may carry out through the winter, as some birds keep their territorial behaviour year round. Coots have ashy-black bodies and black heads where a strikingly contrasting white frontal shield and beak is one of their most distinctive features. Unlike the long, thin toes of the Moorhen, coots have lobulated toes with side extensions - similar to a Grebe's - that allow them to dive in search of the algae and underwater plants that form a good portion of their diet.The Coot "flippers"But lets go back to the frontal shield. The size of the shield changes through the year depending on the bird reproductive status. Both males and females have frontal shields although the males' are larger, but both change in parallel, getting bigger in size as the start of the reproductive season approaches, and peaking in February -March.(from Visser 1988)Birds holding a territory have thicker and larger shields than birds not defending one. Experiments on the American Coot, a close relative of the Eurasian Coot, showed that frontal shields enlarged when coots were injected with testosterone pellets, while they become smaller when injected with estradiol. At the same time, the birds climbed up in the pecking order when injected with testosterone due to an increasingly "pugnacious attitude" in the words of Gordon Gullion. The size of the frontal shield in European coots is also correlated with gonadal size. The frontal shield is apparently used for individual recognition and it is an important in territorial disputes or fights. When an intruder enters a territory, the resident bird will lower its head, raise its wings and prominently displaying their shield to the intruder. Like so...A typical posture of an aggressive cootI have much more on stock on Coots, but this will have to do for today.More informationVisser, J. (1988). Seasonal changes in shield size in the Coot Ardea, 76, 56-63Gordon W. Gullion (1951). The Frontal Shield of the American Coot The Wilson Bulletin, 63, 157-166... Read more »
Visser, J. (1988) Seasonal changes in shield size in the Coot. Ardea, 56-63. info:/
- January 31, 2012
- 06:55 PM
- 172 views
The fascinating love life of the Dunnock
I watched a Dunnock today, feeding under the garden table, with that characteristic half hopping half walking way Dunnocks have, pecking here and there things too small to be seen at a distance, maybe seeds or small invertebrates. Dunnocks, or Hedge Sparrows (Prunella modularis) are little birds, which live their lives mostly unnoticed amongst the undergrowth and are easily overlooked or taken for House Sparrows. They have a grey chest and head and chestnut backs with dark stripes, a thin beak and orange legs. Both males and females look similar, females just a bit smaller than males. In gardens they often feed on the ground, under bird tables when there is some cover, and they prefer to skulk than to sit out in the open. Only in the spring, where males sing their weak, warbling song from a prominent perch they are somewhat more likely to be noticed (above). Contrasting with their modest attire and retiring habits the Dunnock shows a variable mating system - including a common arrangement of two males and a female, a system called polyandry- , and a courtship behaviour that can only be described as peculiar. I was lucky enough to witness courting Dunnocks a few years back. This is a sketch of what I saw and my description.Female appears paler, less extensive grey markings than the male. Both individuals are on the ground. The male hops behind the female and she stops a moment with her tail slightly cocked and vibrating her wings, that are dropped. The male pecks her cloaca repeatedly. Female hops away a little, male follows and the same behaviour starts again. Then the intensity increases, the male pecks her cloaca again and the female stops, then the male jumps on the female and there is a flutter What could be the purpose of this bizarre cloaca pecking behaviour? Has it got anything to do with the presence of polyandry? Nick Davies, in a classic paper published almost 30 years ago, provided some answers. He followed a Dunnock population in Cambridge Botanical Gardens. Males outnumbered females due to higher female mortality during winter, and therefore, there was intense male-male competition. He observed several combinations of breeding partners per territory, including male-female pairs, two males and a female (what he called trios), and some more rare cases including two males defending jointly the territories of several females.Monogamous males guarded the female, following her around closely for a few days before she was due to lay and gaining almost exclusive copulations with her. When there are more than one male in a territory the larger male was dominant to the smaller one and fights were common, with the dominant male trying to chase the subordinate away from the female. Although the dominant male got the best share of copulations, the subordinate also got them as he was usually very persistent and mated with the female unnoticed by the dominant male, or when the male lost track of her - often after a fight. In all events of courtship, be monogamous males or not, the female always exposed her cloaca, often a pumping action was noticed and the male pecked it. After cloaca pecking, the female was seen to eject a droplet of fluid. Davies managed to collect three of these droplets and when he examined them under the microscope he found them to contain bundles of sperm. When he watched the female ejecting the drop of sperm, the male copulated with her immediately after. The purpose of the cloaca pecking behaviour appeared clearer: the male stimulates the female to eject stored sperm from the previous mating, allowing the suitor a shot at paternity. This was confirmed by the fact that the more other male spent near his female, the more a male pecked the female and copulated with her, as the male pursued to increase their chances of paternity. Interestingly, the female played an active role in being part of a trio: she tries to obtain copulations from the subordinate male, escaping the guarding of the dominant, despite his efforts: obviously ejecting sperm from the previous mating will offer both males a share of paternity. When a female was observed to have mated with two males, the brood raised was fed by both males. In contrast, if the subordinate male failed to mate with the female, he did not contribute subsequently to raise the chicks. As nestlings fed by two males have a better chance of survival, it appears that is in the female interest to mate with both males.A subsequent study using DNA fingerprinting confirmed what behavioural observations had strongly hinted: monogamous males got 100% paternity, and both dominant and subordinate males fathered chicks (surprisingly more or less equally). The observant reader will notice that the mean paternity of dominant and subordinate do not add to 100% in the polyandry system. This was because an outsider gained access to the female and fathered a chick.(modified from Table 1 from Burke et al 1989).Furthermore, this study showed that the chances of males helping the female rear the brood were dependent on them having sired some of the brood. It appears that the male is able to judge if he has had sufficient access to female to gain some paternity and to be worth the effort of helping her rear the chicks.Although cloaca pecking can be seen as the male bird trying to ensure his paternity, the elaborate courtship of the dunnock also reflects that females are active participants and, that, as they need more than a single male to rear her chicks, this unusual courtship is the way females ensures that both males help her raise her chicks and that she achieves more reproductive success.A pair of Dunnocks in the garden. What would they be up to?More informationDavies, N. (1983). Polyandry, cloaca-pecking and sperm competition in dunnocks Nature, 302 (5906), 334-336 DOI: 10.1038/302334a0Burke, T., Davies, N., Bruford, M., & Hatchwell, B. (1989). Parental care and mating behaviour of polyandrous dunnocks Prunella modularis related to paternity by DNA fingerprinting Nature, 338... Read more »
Davies, N. (1983) Polyandry, cloaca-pecking and sperm competition in dunnocks. Nature, 302(5906), 334-336. DOI: 10.1038/302334a0
Burke, T., Daviest, N., Bruford, M., & Hatchwell, B. (1989) Parental care and mating behaviour of polyandrous dunnocks Prunella modularis related to paternity by DNA fingerprinting. Nature, 338(6212), 249-251. DOI: 10.1038/338249a0
- January 28, 2012
- 07:01 PM
- 220 views
Opportunistic crows
Corvids are omnivorous birds and display a very flexible and opportunistic feeding behaviour: they will exploit coastal resources when near beaches, will actively search for nests in the spring looking for eggs or chicks, will take advantage of human scraps, feed on roadkill or other carrion, or look for worms and other invertebrates on fields and woodland floor. They show a remarkable inventiveness regarding looking for food, leading in some species to an understanding of the manufacture and use of tools. Rooks are able to add stones to a beaker with a little water where food is floating until the water level rises enough for them to reach the food. Caledonian Crows craft tools - including hooks - from leaves and twigs and use then to fish out grubs from trunks. Other species, like Jays, have extraordinarily precise spatial memory, which allows them to cache food surplus for use later. In general, corvids are dexterous birds. They have excellent foot-beak coordination and often use their feet when feeding, to hold down a piece of food so that they can pick bits with their beaks, as the Carrion Crow above. In experimental set ups, Ravens are able to reach meat tied to a a long string by alternatively pulling with their beaks and stepping on the loops of the string with their foot.Their catholic food preferences and ingenuity have undoubtedly allowed them to adapt to living near people, and some crows species, like the Carrion Crow are common in towns, cities and agricultural land. Carrion Crows and a Greater Black-Backed gull feeding on a dead seal pups and afterbirths on a seal colonyI saw this Carrion Crow flying with a Woodpigeon's egg on its beak. It landed and quickly opened it up and ate the contents The predated egg shellCarrion crow searching for a nest while a blackbird gave alarm calls nearbyCrow feeding on a chick Rooks and Carrion Crow feeding on a beachA short video of a pair of Carrion Crows feeding on the leaf litterMore informationBird, C., & Emery, N. (2009). Rooks Use Stones to Raise the Water Level to Reach a Floating Worm Current Biology, 19 (16), 1410-1414 DOI: 10.1016/j.cub.2009.07.033Hunt, G., & Gray, R. (2004). The crafting of hook tools by wild New Caledonian crows Proceedings of the Royal Society B: Biological Sciences, 271 (Suppl_3) DOI: 10.1098/rsbl.2003.0085Heinrich, B., & Bugnyar, T. (2005). Testing Problem Solving in Ravens: String-Pulling to Reach Food Ethology, 111 (10), 962-976 DOI: 10.1111/j.1439-0310.2005.01133.x... Read more »
Bird, C., & Emery, N. (2009) Rooks Use Stones to Raise the Water Level to Reach a Floating Worm. Current Biology, 19(16), 1410-1414. DOI: 10.1016/j.cub.2009.07.033
Hunt, G., & Gray, R. (2004) The crafting of hook tools by wild New Caledonian crows. Proceedings of the Royal Society B: Biological Sciences, 271(Suppl_3). DOI: 10.1098/rsbl.2003.0085
Heinrich, B., & Bugnyar, T. (2005) Testing Problem Solving in Ravens: String-Pulling to Reach Food. Ethology, 111(10), 962-976. DOI: 10.1111/j.1439-0310.2005.01133.x
- January 20, 2012
- 05:07 PM
- 236 views
Extraordinary feral pigeons
When I make bird lists I do not often tick feral pigeons (Columba livia). They are always there, but I like to take photos of their behaviour.The local flock sitting on the roof, waiting for the sun to rise in the morning, the flock scared by a movement or noise, suddenly taking off and flying in a few elegant circles before settling back; a few of them feeding on the bread that some old lady dutifully brings to the same corner of the street each morning; males in display flight holding their wings high in a V pattern and gliding in a circle.Their leisure times, having a bath......or enjoying the sun on a cold dayDespite their ubiquity, feral pigeons are still extraordinary birds. They are descendants from the Rock Dove, a wild bird of river canyons and sea cliffs, domesticated millennia ago. Some have now have returned to the wild, although still quite attached to humans. Some feral pigeons (above) have very similar plumage patters to their wild ancestor: bluish grey, with a double black wing bars and iridescent neck. Many also keep a trademark white patch in their rumps (like the one bathing on the photo above).Charles Darwin extensively bred many domestic pigeon breeds and dedicated a sizeable section of the first chapter of the Origin of Species to domestic pigeons. He used them to illustrate how domestication had generated distinct races through breeding together animals with certain preferred variations, producing a wide array of diverse shapes, colours, plumages, flight ability and voice from the original ancestral species, the wild Rock Dove. He stressed that this "selection by man" was essentially the same mechanism that his "natural selection". Male pigeons court females by cooing and bowing to them while walking alongside her with puffed feathers, inflated necks and fanned tails, pirouetting occasionally. The courting male, on the left, is also showing his white rump patch. A quick copulation may ensue... As other pigeons, Feral Pigeons lay two eggs per clutch. They nest on ledges inside abandoned buildings, inside roof spaces where they can gain access, or outside, under bridges. Fledged squabs, the young birds (below), have dark eyes, underdeveloped operculum - the white swelling a the base of the beak - and have a look of naivety about them. Both siblings often move about together.Although mortality, even in town, is high. According to research by Alberto Pelleroni and colleagues, the wild-type blue plumage with a white rump affords a survival advantage to feral pigeons, as it decreases the chances of success in Peregrine Falcon attacks. When pigeons with and without the white rump patch had their feathers swapped, the success of the Peregrines reversed accordingly. The presence of Peregrines in the area increased the frequency of the feral pigeon wild type in the area. As for the possible reason for the increased failure of Peregrines in capturing wild-type feral pigeons:All feral pigeons perform the same evasive roll during predation by falcons. The protective white patch may disguise the initiation of the pigeon’s evasive roll by contrasting conspicuous (white patch) and cryptic targets (grey wings and body). A fast flying falcon primed to a conspicuous target centered on the roll might fail to detect the dodge initiated by the cryptic wings as the predator closes from behind. I wonder who ate this squab? Sorry if you are squeamish!Never underestimate pigeons. They have been found to outperform university students in a range of probability calculation tests (see this post for an example). According to Walter T. Herbranson and Julia Schroeder:Pigeons might not possess the cognitive framework for a classical probability-based analysis of a complicated problem [...], but it is certainly not far-fetched to suppose that pigeons can accumulate empirical probabilities by observing the outcomes of numerous trials and adjusting their subsequent behavior accordingly.Update: see this post on pigeon convergenceReferencesHerbranson, W. & Schroeder, J. (2010). Are birds smarter than mathematicians? Pigeons (Columba livia) perform optimally on a ... Read more »
Herbranson, W., & Schroeder, J. (2010) Are birds smarter than mathematicians? Pigeons (Columba livia) perform optimally on a version of the Monty Hall Dilemma. Journal of Comparative Psychology, 124(1), 1-13. DOI: 10.1037/a0017703
Palleroni, A., Miller, C., Hauser, M., & Marler, P. (2005) Predation: Prey plumage adaptation against falcon attack. Nature, 434(7036), 973-974. DOI: 10.1038/434973b
- January 17, 2012
- 05:25 PM
- 198 views
The hybrid goose in the park
I have known this goose since 2005. It is a hybrid between Canada Goose and possibly Greylag, and it turns up every winter in my local park. Today, it behaved gallantly, chasing away other geese and ducks while its partner, a Canada goose, fed.The hybrid goose holds the pair of Canada away from the food source, allowing his partner to feed unmolested.This goose is a large bird, with a mixture of features from both species (see photos of Greylag and Canada below), with the white patch on the face of the Canada, the pink legs of the Greylag and a beak half, black half pink.A Canada goose A Greylag I think the hybrid is a male. He is paired with a female Canada and travels with a Canada flock. Hybridisation is a fascinating issue. In a puritanical view of species - which were created, would not change and could be nicely put into separate drawers - hybrids, were viewed as oddities: unnatural, often sterile, hard to put away in a neat drawer. This view has changed a lot lately. Recent genome sequencing data have shown that we humans seem to be a melange of different hominid isolates that mixed when they met; polar bears and brown bears have been shown to have often interbred during the Pleistocene; Carrion Crows and Hooded Crows do it; Willow Grouse and Rock Ptarmigan do it as well. There are many more examples. Natural climatic changes, such as during ice ages, often brings species together facilitating hybridization. Human introductions, placing species that previously didn't come together in the same areas can also promote hybridisation. Hybridisation is not only more frequent in nature than previously thought, but can also fuel species diversification and adaptation. Geese hybridisation is interesting as, when young, goslings undergo a phenomenon called imprinting. After hatching, goslings have a sensitive period during which they attach themselves socially to any moving stimulus, and follow it. This usually happen to be their parents, but they will eagerly follow people when goslings are hatced in an incubator. Even their mating preferences are determined to some point early in life, as goslings imprint on the adults that rear them - this is called sexual imprinting - and, when adults, will try and find a mate of the same species of the individuals that reared them. In nature, errors can happen. For example when individuals practice egg parasitism - laying eggs on another species' nest - or a brood from another species is adopted or brood amalgamation, when goslings from different species pool together and the adults of one of the species take care of them. What happens to the fostered brood when they grow up? They imprint on their foster parents, which rear them as if they were their offspring, but they still look like their biological parents. Eric Fabricius carried out an experiment in the wild to examine the effects of sexual imprinting on hybridisation in geese. He swapped all eggs from two nests of Canada geese by Greylag eggs. The cross-fostered Greylags migrated with their Canada parents and upon returning to the breeding ground the following spring they paired up:Of 35 returning birds, all 16 females paired with greylag goose males (100%) whereas of 19 males 5 paired with Canada goose females (14%) and the remaining 14 with greylag goose females (74%). The pair bonds generally persisted as long as both birds were present, but after loss of a partner, the remaining bird usually re-mated. Even when this happened several times during the lifetime of a male, the new mate was always a Canada goose female, showing that the males were sexually imprinted to this species. The Canada goose females which had mated with the greylag ganders also remated when widowed, but their new mate could be either a Canada goose or a greylag goose.All cross-fostered females paired with Greylags. They looked like greylags, so they weren't courted by Canada males, just Greylag males. The pattern in the males is interesting, as they probably actively courted Canada females - and some accepted them- but they were also found attractive by greylag females and they ended up pairing with them. Only the category of cross-fostered males pairing with Canada are likely to father hybrid offspring. What happens to the hybrid offspring is interesting as they do look intermediate between species. If is still unclear if hybrid CanadaxGreylags are fertile. The hybrid in the park then probably had a cross-fostered dad. He appears to have no trouble keeping a mate, and if he is always as considerate in his behaviour as today, she might as well keep him.ReferencesFabricius, E. (2010). Interspecific Mate Choice Following Cross-fostering in a Mixed Colony of Greylag Geese (Anser anser) and Canada Geese (Branta canadensis). A Study on Development and Persistence of Species Preferences1 Ethology, 88 (4), 287-296 DOI: 10.1111/j.1439-0310.1991.tb00283.x... Read more »
Fabricius, E. (2010) Interspecific Mate Choice Following Cross-fostering in a Mixed Colony of Greylag Geese (Anser anser) and Canada Geese (Branta canadensis). A Study on Development and Persistence of Species Preferences1. Ethology, 88(4), 287-296. DOI: 10.1111/j.1439-0310.1991.tb00283.x
Edwards, C., Suchard, M., Lemey, P., Welch, J., Barnes, I., Fulton, T., Barnett, R., O'Connell, T., Coxon, P., Monaghan, N.... (2011) Ancient Hybridization and an Irish Origin for the Modern Polar Bear Matriline. Current Biology, 21(15), 1251-1258. DOI: 10.1016/j.cub.2011.05.058
Quintela, M., Thulin, C., & Höglund, J. (2010) Detecting hybridization between willow grouse (Lagopus lagopus) and rock ptarmigan (L. muta) in Central Sweden through Bayesian admixture analyses and mtDNA screening. Conservation Genetics, 11(2), 557-569. DOI: 10.1007/s10592-009-0040-9
- December 20, 2011
- 05:18 PM
- 266 views
Marsupial water slaters
Water slaters or water-lice, Asellus aquaticus, scurry about the leaf litter of my indoor pond. They are fascinating pond inhabitants, always active, sometimes three individuals walking in a line across the tank walls. Most of the water slaters had broken antennae when I collected them, but they have now grown back, the new segments were still thin and transparent a few weeks ago (above), but have now fully developed. Unlike insects, which have very limited regeneration abilities, crustaceans can regenerate lost or broken appendages - as even when adults they carry on molting, and in each molt, they regenerate a bit more of the missing leg or antenna.Water slaters tolerate a wide range of ecological conditions and are distributed across much of temperate Europe, Russia and North America. They are often abundant in polluted water and live in lakes, rivers, springs and even caves - where albino subspecies with smaller eyes have evolved. Being scavengers, they just need some detritus and fallen leaves and organic material to subsist.In the last few days, a female has laid eggs into her brood pouch or marsupium. While she climbed over the leaves beside the tank wall, I took a photo where her yellow eggs are visible through the transparent brood pouch.The marsupium is made of overlapping flat blades coming out of the female's anterior four pair of legs, and allows the mother to hold the brood under her body. This structure is a common feature of all Isopods - which include also terrestrial woodlice. The female not only carries the eggs but also the developing larvae. The larvae will emerge as miniature versions of the adults (see the figure below).Fig. I. Marsupial stages of Asellus aquaticus. Top plate: A, stage A showing two membranes (arrows). B, stage B showing one membrane (arrow) and cleft yolk mass. C, stage B shedding membrane to reveal lateral outgrowth (arrow). D. stage C with its comma shape surrounded by a membrane (arrow). Bottom plate: A, stage C shedding membrane (arrow) to reveal stage D with free appendages. B, stage D with lateral outgrowth (arrow) and appendages covered i n a closely-fitting membrane. C, stage E showing setose body and appendages (arrows). It is at this stage that the juvenile leaves the marsupium to become free-living (from Holdich & Tolba 1981)Occasionally females expel some larvae from the pouch - possibly due to physical limitations of how many she can carry as they grow - and larvae can also develop normally outside the marsupium from developmental stage B. Probably they need the ventilation and extra oxygen produced by the mother in the initial stage. Carrying the eggs and larvae is also bound to offer them some protection from predators, so it probably evolved as a form of maternal care.Although water slaters normally stop reproducing during the coldest months of the year, my indoor pond is warmer than outside, and this might have triggered the start of reproduction; a situation that also occurs in wild populations downstream thermal power stations where water is warm all year round. More informationVitagliano, G., Fano, E., Marchetti, E., Colangelo, M., & Vitagliano, E. (1991). Importance of longevity, growth, and diapause in the evolution of Asellus aquaticus Bolletino di zoologia, 58 (2), 113-117 DOI: 10.1080/11250009109355740Holdich, D., & Tolba, M. (1981). The effect of temperature and water quality on the in vitro development and survival of Asellus aquaticus (Crustacea: Isopoda) eggs Hydrobiologia, 78 (3), 227-236 DOI: 10.1007/BF00008519... Read more »
Vitagliano, G., Fano, E., Marchetti, E., Colangelo, M., & Vitagliano, E. (1991) Importance of longevity, growth, and diapause in the evolution of Asellus aquaticus. Bolletino di zoologia, 58(2), 113-117. DOI: 10.1080/11250009109355740
Holdich, D., & Tolba, M. (1981) The effect of temperature and water quality on the in vitro development and survival of Asellus aquaticus (Crustacea: Isopoda) eggs. Hydrobiologia, 78(3), 227-236. DOI: 10.1007/BF00008519
- December 19, 2011
- 03:30 PM
- 280 views
Sexual roles and gender conflict in pond snails
I caught these pond snails mating in my indoor tank today. The bluish, tongue-like structure between both snails is the penis of the snail on the background, entering the other snail's mantle cavity. So, that snails is acting as a male, (the one with a walrus-like head resting on its partner's shell) and the other as a female. Pond snails are simultaneous hermaphrodites, all individuals have functional ovaries and testis. The snails can self-fertilise, but if sperm from other individual is present, they prefer to use it. Although reciprocal sperm exchange might appear as a logical reproductive strategy, each individual snail might benefit more from acting as a male or as a female in a particular encounter with a potential partner. For example, large snails are able to invest in energetically demanding eggs, and might prefer to act as a female. Individuals acting as females are limited in the frequency at which they produce eggs, so they might prefer not to mate as often. Male reproductive efficiency might depend more on how many sexual encounters he has had, so snails preferring to be males might want to mate more often.Sexual encounters of pond snails can result in just one of them acting as a male and the other like a female, or in subsequent reciprocation. But, the snails could disagree, what if both mating partner insist on providing, but not receive sperm? This is called gender conflict, and the resolution depends on one of the individuals compromising and adopting its less preferred role, at least initially.Petra Hermann and collaborators studied the effect of age on sex role preferences in the great pond snails, Limnaea stagnalis, disentangling it from the effect of size. They reared three batches of snails that had known ages at the time of the experiments (young, Y, middle age M, and senior, S) and matched them by size.First, they looked at the effect of age on mating interactions in age-matched couples. The chances of copulation decreased strongly with age, with young snails copulating with much higher frequency (80%) than senior snails (30%). Encounters between young snails normally ended in a reciprocal intromission (the individual acting as a female initially, then acting as a male), middle aged and senior snails, in contrast, had mostly unilateral sperm exchanges. Then they set encounters between snails of different ages. When pairing young and middle aged snails, also size-matched, about 25% ended in no copulation, and unilateral encounters were more common than reciprocal. The primary role in the copulation (the snail acting as a male first) was adopted by the young snail in about 80% of the encounters, indicating that the male role is the coveted one for the young snail, and that the fact that reciprocation is rare indicates that the middle ages snail is content acting as a female in unilateral encounters. There is an age related shift in sexual role preferences from male to female.Fig. 6. Sexual interactions between young and middle-aged Lymnaea.(A) Most couples of a young and a middle-aged snail (YM) performed acopulation. The majority of these interactions were unilateral, i.e. the snailsdo not reverse roles after finishing the first copulation. Note that in thecases in which the middle-aged animals acted as primary male all youngpartners reciprocated. By contrast, role reversal occurred in only a smallminority (18%) in the couples in which the middle-aged animals acted asfemale. (B) Younger snails act significantly more often as primary male thantheir middle-aged partner. (modified from Hermann et al 2009)They concluded:Animals in the early phase of the species’ life cycle tend to assure that they act as male (either primary or secondary), independent of the age of their partner (Fig. 7A). Senior animals, by contrast, tend to act preferentially as females. The sexual behaviour of middle-aged animals depends on the age of their partner. Combined with similarly aged partners they either act as male or female. Combined with a younger partner they tend to act as female only. Combined with an older partner, they tend to execute both gender roles and will act as males with a similar probability as younger animalsInterestingly, the snails resolved conflict by engaging in reciprocation. When both agreed on a role the encounters tend to be unidirectional. Note that as these snails store sperm and the partners were not virgins, the lack of interest in copulation of the older snails might stem from the fact that they might have accumulated enough sperm to fertilise their eggs. So although the authors removed the confounding effect of age from their experiments, they failed to account for the effect of sperm storage. The snails' efforts are resulting on these lovely egg masses appearing attached on the walls of the tank.More informationHermann PM, Genereux B, & Wildering WC (2009). Evidence for age-dependent mating strategies in the simultaneous hermaphrodite snail, Lymnaea stagnalis (L.). The Journal of experimental biology, 212 (19), 3164-73 PMID: 19749110... Read more »
Hermann PM, Genereux B, & Wildering WC. (2009) Evidence for age-dependent mating strategies in the simultaneous hermaphrodite snail, Lymnaea stagnalis (L.). The Journal of experimental biology, 212(19), 3164-73. PMID: 19749110
- December 18, 2011
- 04:13 PM
- 311 views
Pholcus Phalangioides, the Daddy Long-leg spider
In dark, forgotten corners of houses and outbuildings, a spindly-legged spider hangs upside down - motionless - from a loose, barely visible web made of very fine threads. It is Pholcus phalangioides, the Daddy Long-leg Spider or Cellar Spider. Today, several hang from underneath a wooden shelf in my outside toilet, including the male above. This species is cosmopolitan but has recently expanded its range northwards in the UK, and it is almost always found associated to buildings.A male showing its palps.Mating pair. After an initial male approach and web and leg tapping, if the female accepts him, the partners approach their ventral surfaces and the male inseminates the female using his palps.Pholcus is a very generalist predator and has no trouble subduing large prey. I have seen it with captured Tegenaria (above) even Dysdera (below), the latter a spider with enormous chelicerae. Pholcus is able to do so thanks to its long legs, as it throws silk to its prey and wraps it on silk while keeping a safe distance. It can also invade other spiders' webs and then makes them vibrate simulating the effect of an entangled prey, in order to attract the owners and catch them, a deceptive behaviour known as aggressive mimicry. It will also eat other spider's eggs and trapped prey. If Pholcus is disturbed in its own web it has a defensive behaviour called whirling: it moves its body rapidly in a circle, becoming a blur, while keeping its legs on the web, this might deter other spiders from entering its web but even so, Pholcus can often capture and eat these spiders. Pholcus is even able to capture and feed on woodlice, which often walk up the walls in my conservatory.Female Pholcus are dedicated mothers. They hold their egg clutch of about 20 to 30 eggs by their chelicerae. The eggs in this clutch are close to hatching. The spiderlings' legs are visible through the egg shell as white threads. The spiderlings stay close to their mother for some days after hatching. She hasn't fed since she laid the eggs and she will have to wait until the spiderlings disperse. Pholcus go through five moults before maturity. The one below is molting.Apparently, the most effective enemy of these spiders is that noisy generalist predator, the vacuum cleaner.More informationCheck this website for detailed information on Pholcidae.Maciej Bartos (1998) Quantitative analyses of male courtship behaviour in Pholcus phalangioides(Fuesslin, 1775) (Araneae, Pholcidae). In: P. A. Selden (ed.). Proceedings of the 17th European Colloquium of Arachnology, Edinburgh 1997. 171-176. here.Kazuyoshi Miyashita (1988a) Development of Pholcus Phalangioides (Fuesslin) (Araneae, Pholcidae) under Long and Short Photoperiods. Journal of Arachnology, 16 (1), pp. 126-129.Kazuyoshi Miyashita (1988b) Egg Production in Pholcus Phalangioides (Fuesslin) (Araneae, Pholcidae) under a Constant Temperature and Photoperiod. Journal of Arachnology, 16 (1), 129-131.Jackson, R., & Brassington, R. (1987). The biology of Pholcus phalangioides (Araneae, Pholcidae): predatory versatility, araneophagy and aggressive mimicry Journal of Zoology, 211 (2), 227-238 DOI: 10.1111/j.1469-7998.1987.tb01531.x... Read more »
Jackson, R., & Brassington, R. (1987) The biology of Pholcus phalangioides (Araneae, Pholcidae): predatory versatility, araneophagy and aggressive mimicry. Journal of Zoology, 211(2), 227-238. DOI: 10.1111/j.1469-7998.1987.tb01531.x
- December 11, 2011
- 05:03 PM
- 1,093 views
The CSI Blowfly
At this time of the year, when there has been a few frosts and the sun is weak, the most likely insect you are likely to see on the wing are bluebottles. I found this one yesterday enjoying the sun in my conservatory. It is the urban blowfly, Calliphora vicina, a very cold tolerant species which is the most common buebottle in the UK. Calliphora vicina is one of the most important species in forensic entomology, especially in investigating human remains. Different fly species arrive at a body at different stages of decomposition and they will lay their eggs on it. Blowflies can smell rotting flesh from large distances and are one of the earliest finding a body. They have a very fast life cycle, and they can produce up to five generations a year, depending on the temperature.(Figure from Amendt, Krettek & Zehner 2004)The female lays batches of 150-200 eggs in open wounds, rotten meat, or bodies. These eggs can hatch almost immediately after being laid, but they can take up to 9 days to hatch at 5 oC. The maggost will start feeding immediately. As the duration of each of the three larval stages depend on the temperature and is known in great detail, the age of the oldest maggots together with the average arrival time of the species allows to estimate the post mortem interval and approximate time of death.Bluebottles will enter houses and lay batches of eggs in exposed meat either cooked or raw, and their attraction to rubbish makes them very abundant in cities. Bluebottles have an important ecological role as carcass decomposers...... but they are also pollinators of several plants with exposed nectaries, such as ivy, spurges (Euphorbia) and plants from the carrot family. Some companies have even used bluebottles for greenhouse pollination of various crops as they fly at lower temperatures than bees. They also act as dispersers of fungal spores, and some fungi, like Stinkhorns (Phallus impudicus) have specific adaptations to attract blowflies, releasing chemicals that smell like rotting meat. The flies feed on the surface on the fungus and the spores attach to the fly, which can disperse them. Next time you are annoyed when a bluebottle enters your house, you might want to give a thought to how useful these flies are.More informationAmendt, J., Krettek, R., & Zehner, R. (2004). Forensic entomology. Naturwissenschaften, 91 (2), 51-65 DOI: 10.1007/s00114-003-0493-5Donovan, S., Hall, M., Turner, B., & Moncrieff, C. (2006). Larval growth rates of the blowfly, Calliphora vicina, over a range of temperatures. Medical and Veterinary Entomology, 20 (1), 106-114 DOI: 10.1111/j.1365-2915.2006.00600.x... Read more »
Amendt, J., Krettek, R., & Zehner, R. (2004) Forensic entomology. Naturwissenschaften, 91(2), 51-65. DOI: 10.1007/s00114-003-0493-5
Donovan, S., Hall, M., Turner, B., & Moncrieff, C. (2006) Larval growth rates of the blowfly, Calliphora vicina, over a range of temperatures. Medical and Veterinary Entomology, 20(1), 106-114. DOI: 10.1111/j.1365-2915.2006.00600.x
- December 2, 2011
- 06:50 PM
- 290 views
Caching carrion crow
Many species of the crow family store food when it is plentiful for future use in harder times, a behaviour called caching. Some species rely on stored food more or less all year round, but others might do it occasionally. Carrion crows, Corvus corone, in particular, hoard food when they find some discarded human food, or other, occasionally abundant supply of edible items such as acorns. Today, I was walking along a path when I noticed a carrion crow on the verge. Carrion crows around here are usually very wary of humans and expected it would fly away. It didn't. I stopped with my back to the crow, took my camera slowly out of my bag and took some photos. The crow (above) was indeed very preoccupied with a few pieces of food on its beak, putting them down carefully, covering one with leaves, and then moving a few steps and repeating the procedure with another piece. I have watched carrion crows caching food - including chocolate! - before. What happens to this stored food? Do crows remember where they stored it? are these valuable resources to turn into in times of hardship? R.K. Waite carried out observations of caching crows, rooks and magpies in fields near copses. The main items they cached was acorns, and this behaviour was most common in the autumn, although carrion crows also cached large earthworms when they were plentiful. The birds carried the items in their bill or in a pouch under the tongue and hammered the acorn in a hole they had pecked on the ground, covering it afterwards with leafs, tufts of grass, or soil. These corvids are scatter-hoarders, they do not use the same exact location every time, but the stored food was distributed in many sites, often on the fields away from the trees. By January, there were no acorns to be seen on the ground. It is unclear if Carrion Crows remember the exact location of each cached item, although this has been suggested for Rooks, but they might retain a memory of the general area. Waite found out two different retrieving behaviours. In the first type, individuals foraging in the field for invertebrates came across a cached item, apparently, just by chance, and ate it, they carried out looking for invertebrates afterwards. In the second type of behaviour individuals appeared to be actively searching for cached items during winter:On 14 occasions in late winter, flocks of Rooks or pairs of Carrion Crows or Magpies were seen to recover cached acorns in a quite different way. First, acorns were found about 10 times more quickly. Most observations were of birds foraging on fields rarely used at other times, while some birds found more than one acorn during a foraging bout and only eight out of 56 birds took any invertebrates. Second, searching occurred on days when temperatures were significantly below average and invertebrate availability was reducedWaite's analysis shows that recovering cached items is a profitable way of foraging. The time spend storing the food should the taking into account as a cost, but as this happens where there is not a lot of competition, the nesting season is over, and there is a surplus of food, this cost is offset by the benefits of retrieving the food in cold days when foraging for earthworms and other invertebrates is not very profitable. Waite wondered if Rooks, Carrion crows and Magpies acorn caching behaviour might make them inadvertent, but better foresters than the Jay, as inevitably, some acorns will be forgotten or just not needed and will germinate in the spring in the fields, away from established woodland.More informationWaite, R. (1985). Food caching and recovery by farmland corvids Bird Study, 32 (1), 45-49 DOI: 10.1080/00063658509476854... Read more »
Waite, R. (1985) Food caching and recovery by farmland corvids. Bird Study, 32(1), 45-49. DOI: 10.1080/00063658509476854
- November 29, 2011
- 04:23 PM
- 247 views
Great Tit nestlings respond adaptively to different antipredator alarm calls
Young birds are vulnerable. While they are still in the nest they can easily fall prey to cats, snakes or predatory birds, and once they leave it they are still naive and clumsy and they can also be easy prey. Parents, however, can help: they are experienced and know what other animals represent a risk, and they could make a difference by communicating this to their young offspring by using alarm calls. In a recent paper Toshitaka Suzuki showed how Great Tits (above, a fledgling) produce different alarm calls depending of which predator approaches their nest, and how, crucially, nestlings use this information to behave in the most effective way to avoid predation. The main predators for Great Tits in Japan are the Japanese Rat Snake species and the Jungle Crow. Snakes fit into the cavities Great Tits use and can then kill the chicks, while crows can only snatch chicks approaching the nest entrance. Suzuki presented nesting Great Tits with either a stuffed jungle crow (11 nests) or a live snake (10 nests) in a transparent plastic box, and the parents readily responded to the predators with repeated alarm calls.In response to a crow, they continually gave ‘chicka’ alarm calls that were composed of several different types of syllables, but these calls were rarely produced in the snake trials. Instead, when detecting a snake, parents produced ‘jar’ alarm calls that were composed of harsh syllables. Such ‘jar’ alarm calls were repeatedly given in response to the snake, but were never uttered for the crow.He recorded the nestlings responses to the parents' alarm call using video cameras set inside the nest. When the nestlings heard the 'chicka' call, they crouched inside the nest, making less likely that a crow would be able to reach them from the entrance hole. In contrast, upon hearing the 'jar' call, all nestlings in the 10 nests tested with the snake jumped hurriedly out of the nest. Snakes can easily enter the nest, so early fledgling is the only chance of escape. The parents took care of the early fledged nestlings as normal for fledglings. Although early fledgling can mean lower chances of survival, it is a better option to an almost certain death when a snake enters the nest.This study shows that parent offspring communication can be quite nuanced, and hints at how little we still understand important aspects of the behaviour of common bird species.ReferencesSuzuki TN (2011). Parental alarm calls warn nestlings about different predatory threats. Current biology : CB, 21 (1) PMID: 21215927... Read more »
Suzuki TN. (2011) Parental alarm calls warn nestlings about different predatory threats. Current biology : CB, 21(1). PMID: 21215927
- November 16, 2011
- 05:20 PM
- 419 views
Is global warming erasing a melanism cline?
The 2 spot ladybirds, Adalia bipunctata, I find in my garden are of the typical morph, red with 2 black spots, one in the centre of each wing case, but there is also a melanic morph in this species - black with four red spots - and several rarer intermediate morphs, which are determined genetically. Some colour morphs tend to be more common in some areas than in others. This geographic variation is thought to reflect differences in temperature regulation between morphs. Melanic ladybirds benefit from thermoregulating more effectively in certain microclimates: when there is little, intermittent sunshine and is colder. This advantage becomes most important in early spring, when after emerging from hibernation ladybird behaviour is strongly limited by temperature, so the black ladybirds can start reproducing earlier. Paul Brakefield and Peter de Jong have studied the polymorphism in the two spot ladybird in Holland for 30 years. The two spot colour polymorphism, nicely matched the differences in climate between the warmer coast and the colder inland areas. At the beginning of their study period, in 1980, the dark morph was commonest inland, where it reached 60%, and its frequency decreased gradually towards the coast (less than 20%). Samples taken in the same transect since then show how the sharp decline in frequency of the dark morph gradually disappeared to the point that there was little if no differences between sampled areas in 2004, with the frequency of the melanics in inland areas dropping to similar levels than the frequency in coastal areas. Brakefield and de Jong think that the disappearance of this cline is a response of the ladybirds to the gradually warming climate in the area.Figure 1 Changes over time in the proportion of the illustrated melanic and non-melanic morphs of the two-spot ladybird beetle along a transect of ca. 115 km in length in the Netherlands (bottom-left). Samples were collected in each of the 5 years indicated at 16 more or less evenly spaced localities from west to east. Colouring of years matches the histograms for melanic frequency in the individual samples from each locality. The panel on the bottom-right shows deviations in average temperature from a ‘normal’ season/year at De Bilt (red spot on map). From left to right, columns represent data for winter (Wi), spring (Sp), summer (Su), autumn (Au) and the overall year (Tot), respectively, and from top to bottom for different years beginning before the period of ladybird sampling. The colour of each block indicates the extent to which the average temperature in the particular season/year deviated from ‘normal’; white, no deviation, blue, cooler than normal (dark blue more extreme than light blue), red, warmer than normal (dark red more extreme than light red)(from Brakefield & de Jong, 2011)The story has a second dark aspect. The researchers had trouble reaching acceptable sample sizes in the 2004 sampling season. They even failed to find 2 spot ladybirds in two localities where they previously had been abundant. They attribute the decrease in numbers of the 2 spot ladybird to the impact of the invasive harlequin ladybird, which reached Holland in 2002. Not only the melanism cline is gone, but the 2 spot seems to be dissapearing as well.ReferencesBrakefield PM, & de Jong PW (2011). A steep cline in ladybird melanism has decayed over 25 years: a genetic response to climate change? Heredity PMID: 21792220... Read more »
Brakefield PM, & de Jong PW. (2011) A steep cline in ladybird melanism has decayed over 25 years: a genetic response to climate change?. Heredity. PMID: 21792220
- November 14, 2011
- 05:42 PM
- 415 views
The Migrant Hawker
The Migrant Hawker, Aeshna mixta, is one of the commonest dragonflies found away from water. It regularly visits my pond-less garden, with a clearly marked peak in the second half of August (the male on the top shot from 15th August this year). This species is a fast developer, their larvae take just a year to become adults, but it is sensitive to the cold. Adults are not territorial and are often found hunting together, at high, patrolling over the garden hawking for insects. Early in the morning they rest hanging from vegetation, sunbathing, at about 1-2 m high, often a pair not far from one another, and they then allow close approach.A female Migrant Hawker basking, with another individual on the background (16/08/06) - which I only noticed when checking the photos.Although dragonfly migration has been known for over a century, it is still a little known phenomenon. Several British dragonfly species are regular long-distance migrants, like the Four Spotted Chaser and the Common and Ruddy Darters, and others occasionally appear as vagrants from the Mediterranean or even from North America. Where do they go and why do they do it? Do they migrate back and forth or do they just wander? Is this behaviour to avoid overcrowding or drought, in search for good sites for reproduction? David and Elizabeth Lack (1951) favoured the existence of large scale two way migration in dragonflies, like that of many birds and butterflies, after observing large numbers of Common Darters passing over a high mountain pass in the Pyrenees. American migrants tend to be species breeding in ephemeral or semipermanent ponds, which dry frequently, so migration might also be a wandering in search of suitable ponds. Recently, a combination of miniaturised radio transmitters, isotope analysis and genetic markers have shed light into the migratory behaviour of the American common green darner, Anax junius. The Migrant Hawker has been seen forming large swarms, but, unfortunately, we know very little about the migration in this species. In any case, its migratory behaviour makes it a very good coloniser. In the early 20th century it was regarded as a scarce immigrant, but singe an invasion in 1935 it has been steadily and rapidly expanding its range northwards and westwards in the UK, reaching Scotland in 2004. The species also colonised Ireland in 2000 and is now well established. I can't wait to find out more about these fascinating garden visitors.ReferencesWikelski, M., Moskowitz, D., Adelman, J., Cochran, J., Wilcove, D., & May, M. (2006). Simple rules guide dragonfly migration Biology Letters, 2 (3), 325-329 DOI: 10.1098/rsbl.2006.0487Lack, D. & Lack, E. (1951). Migration of Insects and Birds Through a Pyrenean Pass The Journal of Animal Ecology, 20 (1) DOI: 10.2307/1644E.S. Dyatlova & V.J. Kalkman (2008). Massive migration of Aeshna mixta and Sympetrummeridionale in the Ukrainian Danube delta (Odonata-Anisoptera: Aeschnidae, Libellulidae) Entomologische Berichten, 68, 188-190Brian Nelson, Colm Ronayne & Robert Thompson (2003). Colonization and Changing Status of Four Odonata Species, Anax imperator, Anax parthenope, Aeshna mixta and Sympetrum fonscolombii, in Ireland 2000-2002 The Irish Naturalists' Journal, 27 (7), 266-272... Read more »
Wikelski, M., Moskowitz, D., Adelman, J., Cochran, J., Wilcove, D., & May, M. (2006) Simple rules guide dragonfly migration. Biology Letters, 2(3), 325-329. DOI: 10.1098/rsbl.2006.0487
David, ., & Lack, E. (1951) Migration of Insects and Birds Through a Pyrenean Pass. The Journal of Animal Ecology, 20(1), 63. DOI: 10.2307/1644
E.S. Dyatlova and V.J. Kalkman. (2008) Massive migration of Aeshna mixta and Sympetrum meridionale in the Ukrainian Danube delta (Odonata- Anisoptera: Aeschnidae, Libellulidae). Entomologische Berichten, 188-190. info:/
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