Among-individual variation of risk-taking behaviour in group and solitary context is uncorrelated but independently repeatable in a juvenile Arctic charr (Salvelinus alpinus) aquaculture strain

Behavioural traits have been shown to have implications in fish welfare and growth performances in aquaculture. If several studies have demonstrated the existence of repeatable and heritable behavioural traits (i.e., animal personality), the methodology to assess personality in fishes is often carried out in solitary context, which appears to somewhat limit their use from a selective breeding perspective because these tests are too time consuming. To address this drawback, group-based tests have been developed. In Nordic country, Arctic charr (Salvelinus alpinus) is widely used in aquaculture, but no selection effort on behavioural traits has yet been carried out. Specifically, in this study we examined if risk-taking behaviour was repeatable and correlated in group and solitary context and if the early influences of physical environment affect the among-individual variation of behavioural trait across time in order to verify whether a group risk-taking test could be used as a selective breeding tool. Here, we found that in both contexts and treatments, the risk-taking behaviour was repeatable across a short period of 6 days. However, no cross-context consistency was found between group and solitary, which indicates that Arctic charr express different behavioural trait in group and solitary.

Prioritised Learning in Snowdrift-Type Games

Cooperation is a ubiquitous and beneficial behavioural trait despite being prone to exploitation by free-riders. Hence, cooperative populations are prone to invasions by selfish individuals. However, a population consisting of only free-riders typically does not survive. Thus, cooperators and free-riders often coexist in some proportion. An evolutionary version of a Snowdrift Game proved its efficiency in analysing this phenomenon. However, what if the system has already reached its stable state but was perturbed due to a change in environmental conditions? Then, individuals may have to re-learn their effective strategies. To address this, we consider behavioural mistakes in strategic choice execution, which we refer to as incompetence. Parametrising the propensity to make such mistakes allows for a mathematical description of learning. We compare strategies based on their relative strategic advantage relying on both fitness and learning factors. When strategies are learned at distinct rates, allowing learning according to a prescribed order is optimal. Interestingly, the strategy with the lowest strategic advantage should be learnt first if we are to optimise fitness over the learning path. Then, the differences between strategies are balanced out in order to minimise the effect of behavioural uncertainty.

Ain’t going down without a fight: state-and environment-dependence of antipredator defensive aggressive personalities in Carpetan rock lizard

Aggression is one of the most frequently studied behavioural traits across a wide range of taxa; however, most studies evaluate aggressive behaviour in a social context, in which aggressive interactions between conspecifics are motivated by resource control (offensive or social aggression). However, in an antipredator context, the primary role of aggression is defence (defensive or antipredator aggression). Although the neuroendocrinology of antipredator aggression is often studied in domesticated and laboratory animals, how environment and individual state affect this behavioural trait in the wild is largely unknown. Here, by conducting a manipulative experiment, we tested whether (i) consistent between-individual differences (i.e. animal personality) are present in antipredator aggression in adult male Carpetan rock lizards (Iberolacerta cyreni) and (ii) short-term environmental changes (presence vs. absence of predator cues) and differences in individual state (body length, head size, hind limb length) affect individual mean behaviour (i.e. behavioural type). We found moderate-high repeatability in antipredator aggression (willingness to bite a human), indicating the presence of animal personality in this behavioural trait. Lizards were on average more defensive in the presence of predator cues; furthermore, short-legged males showed higher antipredator aggression than long-legged males in the presence of predator cues, probably as an attempt to balance their decreased escape speed. Larger (~ older) males were more defensive than smaller ones, probably due to their increased fighting ability. We conclude that antipredator aggression is an important part of an individual’s behavioural repertoire and its expression is driven by both environmental situation and individual state. Significance statement Antipredator/defensive aggression is not the primary antipredatory response; however, when other ways of escape are not possible, actually hurting the predator could be the only way of survival. While this behaviour obviously has substantial effects on fitness, it is severely understudied compared to social/offensive aggression. In a manipulative experiment, we found that there are consistent between-individual differences in antipredator aggression (i.e. willingness to bite during handling) of adult male Carpetan rock lizards (Iberolacerta cyreni), supporting the presence of animal personality and suggesting that this behavioural trait might respond to natural selection. Furthermore, short-term environmental variation (i.e. presence vs. absence of predator cues) in interaction with individual state affected antipredator aggression of individuals, emphasising the ecological and evolutionary relevance of this behaviour.

Predation as a driver of behavioural variation and trait integration: effects on personality, plasticity, and predictability

Predation is increasingly viewed as an important driver in maintaining ecological and phenotypic diversity. In contrast to classic evolutionary theory which predicts that predation will shift trait means and erode variance within prey species, several studies indicate higher behavioural trait variance and integration in high predation populations. These results come predominately from field-sampled animals that cannot isolate the role of predation from other ecological factors such as density. Here, we study the role of predation on behavioural trait (co-)variation in density-controlled populations of guppies (Poecilia reticulata) living with and without a benthic ambush predator. At 2.5yrs post introduction of the predators (up to 10 overlapping generations), 40 males were sampled from each of the six populations and extensively assayed for activity rates, water-column use and voracity. Individual variation was pronounced in both treatments, with substantial individual variation means, temporal plasticity and predictability. The effects of predation were subtle. Predators had little effect on mean behaviour, though predator-exposed fish spent more time at the surface in early trials, which decreased to the same as controls with time. Predators did however affect the integration of behavioural traits. In predator exposed ponds, guppies that were higher in the water-column fed slower and had a reduced positive correlation with activity, relative to control populations. Predators also affected the integration of personality and plasticity – leading to changes in among-individual variances through time in water-column use and activity – which was absent in controls. Our results contrast with the extensive guppy literature showing rapid evolution in trait means, and shows maintenance of behavioural variance under predation.

Evolutionary GEM: Crocodilian Vocalizations

The clade, Archosauria, encompasses crocodilians and birds. Both crocodilians and birds exhibit vocalizations to communicate a variety of behaviours including courtship, distress, and aggression. The similarity in vocalization behaviours of modern day Archosauria suggests that vocal communication may be a conserved behavioural trait also exhibited by ancient Archosauria.

On the Chemical Disguise of a Physogastric Termitophilous Rove Beetle

Inter-specific symbiotic links are often reinforced by morphological, physiological, or behavioural trait modification undergone by the associated species. In some cases, such as in physogastric termitophile staphylinids, such modifications do facilitate the social interaction. Here we inspect chemical traits of the physogastric staphylinid Corotoca melantho (Insecta: Coleoptera) and its termite host Constrictotermes cyphergaster (Insecta: Blattodea: Isoptera), aiming to verify whether staphylinids resemble their host. First, we compared CHC profiles of hosts and guests within and among termitaria, to gather evidence on the origin of such profiles in guests. Then, we examined nitrogen and carbon isotopic signatures of these cohabitants to inspect whether chemical disguise is achieved by predation of host workers by staphylinids. Beetles presented CHC more similar to the CHC of their cohabiting termites than to (i) their conspecifics and (ii) termites from another nest, thereby favouring the hypothesis on CHC acquisition by guests. Isotopic signatures revealed that such similarities could not be majorly determined by share nutrition between these cohabitants. In general, our results evidenced that chemical disguise in termitophiles may function as a strategy for social integration in morphological mimics.