Collective Animal Behavior from Bayesian Estimation and Probability Matching

Animals living in groups make movement decisions that depend, among other factors, on social interactions with other group members. Our present understanding of social rules in animal collectives is based on empirical fits to observations and we lack first-principles approaches that allow their derivation. Here we show that patterns of collective decisions can be derived from the basic ability of animals to make probabilistic estimations in the presence of uncertainty. We build a decision-making model with two stages: Bayesian estimation and probabilistic matching.
In the first stage, each animal makes a Bayesian estimation of which behavior is best to perform taking into account personal information about the environment and social information collected by observing the behaviors of other animals. In the probability matching stage, each animal chooses a behavior with a probability given by the Bayesian estimation that this behavior is the most appropriate one. This model derives very simple rules of interaction in animal collectives that depend only on two types of reliability parameters, one that each animal assigns to the other animals and another given by the quality of the non-social information. We test our model by obtaining theoretically a rich set of observed collective patterns of decisions in three-spined sticklebacks, Gasterosteus aculeatus, a shoaling fish species. The quantitative link shown between probabilistic estimation and collective rules of behavior allows a better contact with other fields such as foraging, mate selection, neurobiology and psychology, and gives predictions for experiments directly testing the relationship between estimation and collective behavior

Finding a place to live: conspecific attraction affects habitat selection in juvenile green and golden bell frogs

Conspecific attraction plays an important role in habitat selection of several taxa and can affect and determine distribution patterns of populations. The behaviour is largely studied and widespread among birds, but in amphibians, its occurrence seems limited to breeding habitats of adults and gregarious tadpoles. The Australian green and golden bell frogs (<i>Litoria aurea</i>) have suffered considerable shrinking of their original distribution in south-eastern Australia since the 1970s. Currently, with only about 40 populations remaining, the species is considered nationally threatened. In natural conditions, these frogs are aggregated in the landscape and do not seem to occupy all suitable ponds within the occurrence area. To date, studies focusing on the frogs' habitat have failed in finding a general habitat feature that explains current or past occupancy. This led us to the hypothesis that social cues may play a key role in habitat selection in this species. Using two choice experiments, we tested the preference of juvenile green and golden bell frogs for habitats containing cues of conspecifics of similar size versus habitats without conspecific cues. Tested frogs did not show a preference for habitats containing only scent from conspecifics but did prefer habitats where conspecifics were present. Our results show that conspecific attraction is a determining factor in juvenile green and golden bell frog habitat selection. To our knowledge, this is the first time the behaviour is shown to occur in juvenile frogs in the habitat selection context. From a conservation management point of view, the behaviour may help to explain the failure of reintroductions to areas where the frogs have been extinct, and the non-occupation of suitable created habitats in areas where they still inhabit and develop appropriated management strategies