In October 2014, the results of a study1 led by David M. P. Jacoby, Lauren N. Fear, David W. Sims, and Darren P. Croft of the University of Exeter and the Marine Biological Association of the UK (MBA) were published in the Behavioral Ecology and Sociobiology journal. The study focused on captive populations of Small-spotted catsharks (Scyliorhinus canicula), and the results give strong indications that sharks have personalities.
“We define personality as a repeatable behaviour across time and contexts. What is interesting is that these behaviours differ consistently among individuals. This study shows, for the first time, that individual sharks possess social personalities… In the wild these small juveniles can make easy prey items for larger fish, so different anti-predator strategies are likely to have evolved. More research, however, is required to truly test the influence of predators on social personality traits in sharks. This study is the first step in that direction.” said Professor Croft.
The researchers observed the social interactions of these sharks as they were moved among three different tank habitats.
“We found that even though the sizes of the groups forming changed, socially well-connected individuals remained well-connected under each new habitat. In other words, their social network positions were repeated through time and across different habitats.” reported Dr. Jacoby. “These results were driven by different social preferences (i.e social/antisocial individuals) that appeared to reflect different strategies for staying safe. Well-connected individuals formed conspicuous groups, while less social individuals tended to camouflage alone, matching their skin colour with the colour of the gravel substrate in the bottom of the tank.”
The paper’s abstract:
Interest in animal personalities has generated a burgeoning literature on repeatability in individual traits such as boldness or exploration through time or across different contexts. Yet, repeatability can be influenced by the interactive social strategies of individuals, for example, consistent inter-individual variation in aggression is well documented. Previous work has largely focused on the social aspects of repeatability in animal behaviour by testing individuals in dyadic pairings.
Under natural conditions, individuals interact in a heterogeneous polyadic network. However, the extent to which there is repeatability of social traits at this higher order network level remains unknown. Here, we provide the first empirical evidence of consistent and repeatable animal social networks. Using a model species of shark, a taxonomic group in which repeatability in behaviour has yet to be described, we repeatedly quantified the social networks of ten independent shark groups across different habitats, testing repeatability in individual network position under changing environments.
To understand better the mechanisms behind repeatable social behaviour, we also explored the coupling between individual preferences for specific group sizes and social network position. We quantify repeatability in sharks by demonstrating that despite changes in aggregation measured at the group level, the social network position of individuals is consistent across treatments. Group size preferences were found to influence the social network position of individuals in small groups but less so for larger groups suggesting network structure, and thus, repeatability was driven by social preference over aggregation tendency.
This article was written by Amanda Pachniewska, founder & editor of AnimalCognition.org
1 – David M. P. Jacoby, Lauren N. Fear, David W. Sims, Darren P. Croft
Shark personalities? Repeatability of social network traits in a widely distributed predatory fish
Behavioral Ecology and Sociobiology