Mechanisms of recognition in birds and social Hymenoptera: from detection to information processing

Neural correlates of individual facial recognition in a social wasp

Individual recognition is critical for social behavior across species. Whether recognition is mediated by circuits specialized for social information processing has been a matter of debate. Here we examine the neurobiological underpinning of individual visual facial recognition in Polistes fuscatus paper wasps. Front-facing images of conspecific wasps broadly increase activity across many brain regions relative to other stimuli. Notably, we identify a localized subpopulation of neurons in the protocerebrum which show specialized selectivity for front-facing wasp images, which we term wasp cells. These wasp cells encode information regarding the facial patterns, with ensemble activity correlating with facial identity. Wasp cells are strikingly analogous to face cells in primates, indicating that specialized circuits are likely an adaptive feature of neural architecture to support visual recognition.

Highly diverse cuticular hydrocarbon profiles but no evidence for aggression towards non-kin in the ambrosia beetle Xyleborinus saxesenii

Animal societies use nestmate recognition to protect against social cheaters and parasites. In most social insect societies, individuals recognize and exclude any non-nestmates and the roles of cuticular hydrocarbons as recognition cues are well documented. Some ambrosia beetles live in cooperatively breeding societies with farmed fungus cultures that are challenging to establish, but of very high value once established. Hence, social cheaters that sneak into a nest without paying the costs of nest foundation may be selected. Therefore, nestmate recognition is also expected to exist in ambrosia beetles, but so far nobody has investigated this behavior and its underlying mechanisms. Here we studied the ability for nestmate recognition in the cooperatively breeding ambrosia beetle Xyleborinus saxesenii, combining behavioural observations and cuticular hydrocarbon analyses. Laboratory nests of X. saxesenii were exposed to foreign adult females from the same population, another population and another species. Survival as well as the behaviours of the foreign female were observed. The behaviours of the receiving individuals were also observed. We expected that increasing genetic distance would cause increasing distance in chemical profiles and increasing levels of behavioural exclusion and possibly mortality. Chemical profiles differed between populations and appeared as variable as in other highly social insects. However, we found only very little evidence for the behavioural exclusion of foreign individuals. Interpopulation donors left nests at a higher rate than control donors, but neither their behaviours nor the behaviours of receiver individuals within the nest showed any response to the foreign individual in either of the treatments. These results suggest that cuticular hydrocarbon profiles might be used for communication and nestmate recognition, but that behavioural exclusion of non-nestmates is either absent in X. saxesenii or that agonistic encounters are so rare or subtle that they could not be detected by our method. Additional studies are needed to investigate this further.

Auditory perception of self and others in zebra finches: evidence from an operant discrimination task

Vocal communication is essential for social interactions in many animal species. For this purpose, an animal has to perceive vocal signals of conspecifics and is often also required to discriminate conspecifics. The capacity to discriminate conspecifics is particularly important in social species in which individuals interact repeatedly. In addition, auditory perception of self plays an important role for vocal learners. A vocal learner has to memorise vocalisations of conspecifics and to subsequently modify its own vocalisations in order to match the memorised vocalisations. Here, we investigated auditory perception of self and others in zebra finches (Taeniopygia guttata), a highly gregarious songbird species and vocal learner. We used laboratory colonies in which founder males had been previously trained to produce the same song type. This resulted in artificial dialects in the song of founders and their offspring. We investigated whether those birds would be able to discriminate between familiar and unfamiliar conspecifics based on song. Furthermore, we examined whether they would classify their own song as familiar or unfamiliar. We found that birds were able to discriminate between songs of familiar versus unfamiliar conspecifics, despite the fact that all songs were imitations of the same song type. This suggests that such discrimination is possible even based on songs with a high acoustic similarity. None of the subjects classified their own song as unfamiliar. Three out of eight males classified their own song as familiar. Thus zebra finches might recognise their own song. Further experiments are needed to confirm such self-recognition.