Abstract

Among species providing uniparental care, the caring parent faces time constraints and may have to compromise offspring care/protection for self-maintenance. In most mammalian species females raise their offspring without receiving help from males. Communal nesting, when multiple females share a single nest where they rear their pups together, may have evolved as a mutually beneficial cooperative behaviour to reduce mothers' nest attendance without increasing the time their offspring are left alone. We tested this hypothesis using data collected in a free-living house mouse population where reproduction occurred in nest boxes and was closely monitored. Individuals were fitted with transponders allowing automatic recording of their location, and a genetic parentage analysis confirmed maternal identity. Compared to mothers raising their pups solitarily, communally nesting mothers spent less time inside their nest. Their pups, however, were left alone for a similar amount of time as solitarily raised pups. The time communal litters were left alone did not covary with the kinship of communally nesting females. These results indicate that communally nesting mothers can allocate more time to foraging or territorial defence without impairing the amount of maternal attention received by their offspring. Nevertheless, communally nesting mothers showed some overlap in their stays at the nest. Offspring may benefit from more regular meals while mothers may gain information on the partner's contribution to combined maternal care which could potentially prevent cheating.

Remarks

Featured Article in the June 2014 issue of Animal Behaviour (DOI: 10.1016/j.anbehav.2014.04.039).

Abstract

From the synchronised beauty of fish schools to the rigorous hierarchy of ant colonies, animals often display awe-inspiring collective behaviour. In recent years, principles of statistical physics have helped to unveil some simple mechanisms behind the emergence of such collective dynamics. Among the most elementary tools used to explain group behaviour are random processes, a typical example being the so-called “random walk”. In this paper, we have developed a framework based on such random assumptions to study the spatial and social structure of a population of wild house mice. We introduce the concept of perceptual landscape to describe the spatial behaviour of animals, whilst including all sensory and social constraints they are subject to: the perceptual landscape effectively maps the environment of animals as they perceive it. By applying our assumptions to a multi-agent model, we are able to reveal that much of the high-level social behaviour observed in the mouse population can indeed be explained through the many interactions of randomly moving individuals. This raises the question of how much of what we often regard as complex natural phenomena may, in fact, be the result of exceedingly simple forces.

Abstract

We investigate to what extent the interaction dynamics of a population of wild house mouse (Mus musculus domesticus) in their environment can be explained by a simple stochastic model. We use a Markov chain model to describe the transitions of mice in a discrete space of nestboxes, and implement a multi-agent simulation of the model. We find that some important features of our behavioural dataset can be reproduced using this simplified stochastic representation, and discuss the improvements that could be made to our model in order to increase the accuracy of its predictions. Our findings have implications for the understanding of the complexity underlying social behaviour in the animal kingdom and the cognitive requirements of such behaviour.

Abstract

The measurement of information flows within moving animal groups has recently been a topic of considerable interest, and it has become clear that the individual(s) that drive collective movement may change over time, and that such individuals may not necessarily always lead from the front. However, methods to quantify the influence of specific individuals on the behaviour of other group members and the direction of information flow in moving group, are lacking on the level of empirical studies and theoretical models. Using high spatio-temporal resolution GPS trajectories of foraging meerkats, Suricata suricatta, we provide an information-theoretic framework to identify dynamical coupling between animals independent of their relative spatial positions. Based on this identification, we then compare designations of individuals as either drivers or responders against designations provided by the relative spatial position. We find that not only does coupling occur both from the frontal to the trailing individuals and vice versa, but also that the coupling direction is a non-linear function of the relative position. This provides evidence for (i) intermittent fluctuation of the coupling strength and (ii) alternation in the coupling direction within foraging meerkat pairs. The framework we introduce allows for a detailed description of the dynamical patterns of mutual influence between all pairs of individuals within moving animal groups. We argue that applying an information-theoretic perspective to the study of coordinated phenomena in animal groups will eventually help to understand cause and effect in collective behaviour.

Abstract

Risk-sensitive adaptive spatial organisation during group movement has been shown to efficiently minimise the risks associated with external ecological threats. Whether animals can draw on such behaviours when confronted with man-made threats is generally less clear. We studied road-crossing in a wild, but habituated, population of meerkats living in the Kalahari Desert, South Africa. We found that dominant females, the core member in meerkat social systems, led groups to the road significantly more often than subordinates, yet were consistently less likely to cross first. Our results suggest that a reshuffling occurs in progression order when meerkat groups reach the road. By employing a simple model of collective movement, we have shown that risk aversion alone may be sufficient to explain this reshuffling, but that the risk aversion of dominant females toward road crossing is significantly higher than that of subordinates. It seems that by not crossing first, dominant females avoid occupying the most risky, exposed locations, such as at the front of the group – a potential selfish strategy that also promotes the long-term stability and hence reproductive output of their family groups. We argue that our findings support the idea that animals can flexibly apply phylogenetically-old behavioural strategies to deal with emerging modern-day problems.

Remarks

Extended abstract

Abstract

Several social mammals, including elephants and some primates, whales and bats, live in multi-level societies that form temporary subgroups. Despite these fission-fusion dynamics, group members often maintain long-term bonds. However, it is unclear whether such individual links and the resulting stable social subunits continue to exist after a complete reorganisation of a society, e.g. following a population crash. Here we employed a weighted network analysis on 7109 individual roosting records collected over four years in a wild Bechstein's bat colony. We show that, in response to a strong population decline, the colony's two stable social subunits fused into a non-modular social network. Nevertheless, in the first year after the crash, long-term bonds were still detectable, suggesting that the bats remembered previous individual relationships. Our findings are important for understanding the flexibility of animal societies in the face of dramatic changes, and for the conservation of social mammals with declining populations.

Abstract

Elephants, dolphins, as well as some carnivores and primates maintain social links despite their frequent splitting and merging in groups of variable composition, a phenomenon known as fission-fusion. Information on the dynamics of social links and interactions among individuals is of high importance to the understanding of the evolution of animal sociality, including that of humans. However, detailed long-term data on such dynamics in wild mammals with fully known demography and kin structures are scarce. Applying a weighted network analysis on 20 500 individual roosting observations over 5 years, we show that in two wild Bechstein's bat colonies with high fission-fusion dynamics, individuals of different age, size, reproductive status and relatedness maintain long-term social relationships. In the larger colony, we detected two stable subunits, each comprising bats from several family lineages. Links between these subunits were mainly maintained by older bats and persisted over all years. Moreover, we show that the full details of the social structure become apparent only when large datasets are used. The stable multi-level social structures in Bechstein's bat colonies resemble that of elephants, dolphins and some primates. Our findings thus may shed new light on the link between social complexity and social cognition in mammals.

Remarks

Gerald Kerth and Nicolas Perony contributed equally to the study. Featured in Science Editor's Choice (DOI: 10.1126/science.331.6023.1366-d). Among the Proc. R. Soc. B most-read articles in February 2011.