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Comparative studies of acoustic communication in clades with diverse signal features provide a powerful framework for testing relationships between perception and behaviour. We measured auditory sensitivity in five species of estrildid songbirds with acoustically distinct songs and tested whether differences aligned with species differences in song frequency content. Species were chosen based on phylogeny and differences in song acoustics. Behavioural audiograms were obtained using operant training and testing. Adult audiograms were compared across species and between sexes within a species. Juvenile and adult audiograms were compared in one species. The audiograms of adults reared by their own species and those reared and tutored by another species were compared in one species. Results showed that audiograms were similar across species and similar to previous reports of songbird auditory sensitivity. Species differed in the highest frequency detected and the frequency of peak sensitivity. While hearing frequency range was not correlated with song frequency bandwidth, the frequency of peak sensitivity was highly corelated with the frequency of peak energy in song. Sensitivity did not differ based on sex, age or tutoring experience. Our findings suggest that adaptations in songbird auditory sensitivity are largely constrained by shared peripheral and central encoding mechanisms, with species-specific perception appearing only at peak sensitivity.

Difference in male and female motivation to mate can be attributed to conflicts over investment in gametes and offspring. While such motivations are relatively straightforward in separate-sexed species, they may become intertwined in simultaneous hermaphrodites. Such organisms produce both types of gametes and each sperm donor is also a sperm receiver. For the pond snail, Lymnaea stagnalis, male motivation has been shown to become temporarily low after having donated sperm. Moreover, previous studies indicated that being inseminated can be costly for the sperm recipient's reproductive success because accessory gland proteins transferred in the ejaculate can temporarily lower female and male reproductive success. In addition, potential sperm recipients have been found to exhibit behaviours that suggest that they try to avoid being inseminated. Such behaviours could be motivated via the sperm-receiving, female role in this pond snail. To test this, we experimentally eliminated this species' male role using a simple surgical procedure, thus creating ‘feminized’ snails. We subsequently observed mating behaviour and quantified egg laying and hatching success as a proxy of female reproductive success. Although we did not find an effect of feminization on hatching success, we did find a significant decrease in the occurrence of ‘biting’ behaviour in feminized individuals compared to sham-operated and control snails. Although biting has been proposed to be a female behaviour, it is likely dictated via the male role because feminized hermaphrodites showed less biting, possibly because they no longer had to defend their paternity success. The other prominent recipient behaviour, ‘crawl-out’, was not eliminated when performance of the male role was surgically removed, which suggests that this behaviour is female role motivated. The species and experimental approach used enabled us to disentangle sexual motivations of a simultaneous hermaphrodite and show that not all behavioural components have the same motivational basis.

To overcome the cost of competition resulting from close social proximity while foraging in a group, individuals may balance their use of private (i.e. acquired from personal sampling) and social (i.e. acquired by watching other individuals) information in order to adjust their foraging strategy accordingly. Reliability of private information about environmental characteristics, such as the spatial distribution of prey, is thus likely to affect individual movement and social interactions during foraging. Our aim was to investigate how movement characteristics of foraging individuals changed as they acquired reliable private information about the spatial occurrence of prey in a foraging context. We allowed guppies (Poecilia reticulata) to develop the reliability of their private knowledge about prey spatial occurrence by repeatedly testing shoals in a foraging task under three experimental distributions of prey: 1) aggregated prey forming three patches located in fixed locations, 2) scattered distribution of prey with random locations, or 3) no prey (used as control). We then applied tracking methods to obtain individual time series of spatial coordinates from which we computed a suite of movement variables reflecting search effort, social proximity and locomotion characteristics during foraging, in order to examine changes occurring over repeated trials and to investigate which best explained foraging success. We show that foraging shoals became more efficient at finding and consuming food over the first three days by increasing their time spent active. Over time, individuals foraging on either scattered or aggregated prey travelled greater distances, showed an increasing distance to their closest neighbour and became slightly more stochastic in their acceleration profile, compared to control individuals. We found that behaviour changed as private information increased over time. Social proximity was the major predictor of foraging success in the absence of prior foraging information, while stochasticity in acceleration and search effort became the most important predictors of foraging success as information increased. In conclusion, we show that individual movement patterns changed as they acquire private information. Contrary to our predictions, the spatial distribution of prey did not affect any of the movement variables of interest. Our results emphasise the importance of information, both private and social, in shaping movement behaviour in animals. Keywords: social foraging, movement, private information, prey spatial distribution, fish.

Funding: This work was supported by a University of Kent 50th Anniversary Scholarship, and a Cotutelle de thèse grant from swissuniversities to J.V. Optimal foraging theory has guided much of the research on foraging behaviour in the past five decades, with the notion of optimality deeply embedded in most models today. However, assuming that all foragers strive to maximize a certain predefined currency, such as amount of food per unit time, restricts what can be learned about the factors influencing foraging decisions. Here we applied a different approach: the discrete-choice model, which does not assume an optimal strategy as the starting point, but instead examines foraging decisions directly, modelling interpatch movements as the consequence of a choice of destination from a limited set of options. We analysed a set of foraging decisions by both adult male and female chimpanzees, Pan troglodytes, from two habituated communities in the Budongo forest, Uganda, to investigate the influence of foraging variables including food patch characteristics and interpatch distance on patch choice, with a view to identifying the strategy underlying these decisions. Despite differences in habitat between communities, we found that foraging strategies were remarkably similar across both communities and sexes, with chimpanzees exhibiting a clear preference for closer and novel (not previously visited) food patches. Individuals of both communities frequently chose to forage on food patches providing young leaves, highlighting the importance of this food type in their diet. Contrary to expectation, patch size did not predict foraging decisions, except for adult males of one community that chose larger patches, while both sexes aimed to minimize travel distance between consecutive patches. This study provides the first direct evidence that chimpanzees consider travel distance and whether they have recently visited a patch when choosing between potential foraging sites and demonstrates that new insights can be gained (even in a well-studied system) from integrating several important variables describing feeding ecology into a coherent model of patch choice. Publisher PDF

The ability of a single genome to express multiple phenotypes is key to understanding social evolution, where individuals with different morphologies perform different tasks. In social insects, phenotypes are typically determined during larval development and depend on the social environment. Here, we used the bumble bee Bombus impatiens to examine the social regulation of body size variation and caste by manipulating the identity (queen/worker) and the number of caretakers tending for the brood. Eggs of females and males were kept in cages with (1) a single queen; (2) a single worker; (3) three workers; or (4) ten workers. We measured larval weight, developmental length, and the resulting caste (in females) throughout the brood development of >2000 individuals. We found differences in larval mass when reared by varying number of workers, but not when reared by a single worker compared to a queen. Additionally, in contrast with previous findings in B. terrestris, none of the female eggs reared by workers developed into gynes (new queens), indicating that the mechanisms regulating caste determination in B. impatiens is not solely dependent on the queen presence as in B. terrestris. Adult males were slightly larger than workers and developed for a longer period in the presence of the queen. Overall, we suggest that body size in B. impatiens is determined by the number of caretakers and is likely mediated by the amount of provision. The hypothesis that the queen’s presence manipulates female caste was not supported by our data.

Intraspecific interactions shape animal social networks and regulate population dynamics. Species with solitary life histories rely on communication cues for population regulation, especially olfaction for many terrestrial mammals. Increasing evidence shows complex social structures among presumably solitary species and although social factors may play a key role in spatial organization, we lack insights into how species with solitary life histories structure and maintain sociospatial systems. Herein, we applied a social network approach to decode leopard, Panthera pardus, behaviour and interactions at marking sites that we monitored with camera traps. We found that leopard social units within our study area consisted of up to five individuals and that same-sex and opposite-sex interactions were equally likely to occur. Individuals behaved and responded differently depending on the type of interaction, serving both ter-ritorial and reproductive purposes. Temporal segregation allowed intersexual co-occurrence, while same-sex co-occurrence may be facilitated through familiarity with stable neighbours. Central in-dividuals interacted within and outside their social unit and appeared fundamental to group stability. The removal of these individuals, such as through legal harvest or pre-emptively as an attempt to minimize depredation, may weaken social cohesion and ultimately affect population demography. Our findings on intraspecific co-occurrence in a solitary carnivore depict a complex social structure that can be important for population stability and might occur in other solitary species.(c) 2023 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.