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A Small Shark With a Big Personality

"Personality" is no longer a trait which is only assigned to human beings. In fact, personality - defined as individual differences in behaviour which are consistent across both time and contexts - has been proven in over 200 species! Including mammals, amphibians, molluscs, birds, fishes and even insects! So how exactly is 'personality' defined? Do sharks have personalities? And why?


Lesser spotted catshark in a complex reef habitat (Image source: https://commons.wikimedia.org)

What is 'Personality'?

When psychologists discuss human personality, we are defined based on 'the big 5' behavioural axes, named 1. Openness to experience, 2. Extraversion, 3. Conscientiousness, 4. Agreeableness and 5. Neuroticism.


If you want to learn more about your personality type, you can take a Myers-Briggs test.


However, in animals behaviours are defined differently. Conscientiousness and has only been found in very few animal species. Instead, generally, animal personalities are explored based upon individual differences in: 1. Activity, 2. Aggression, 3. Boldness, 4. Explorativeness and 5. Sociability (Conrad et al, 2011).


Port Jackson sharks have been proven to have individual personalities (Image Credit: Mark Norman / WikimediaCommons)

Some Sharks are more Social than Others

Researching personality in animals is a relatively new field, but becoming increasingly popular amongst scientists. So now, we have started to see studies of shark personality! For example, we now know that some sharks are more bold or more explorative compared to other individuals of the same species. To learn more, check out Fortune Favours the Brave.


Small spotted catsharks have individual personalities which are consistent across time and contexts (Image Credit: H. Zell / WikimediaCommons)

Scientists have also learned that shark differ in how social they are. When assessing sharks in several different habitats, and considering both the size of the group and each individual shark's position within the network, scientists have found that certain small spotted catsharks (Scyliorhinus canicula) are consistently more sociable than others. Whatsmore certain sharks preferred to associate with specific individuals... Basically they have friends (Jacoby et al, 2014).




Shark Friendships are a Result of Evolution

The researchers hypothesised that having consistent social partners might allow the small spotted catsharks social stability and social cohesion. This is particularly important in prey species, like these catsharks, because grouping together can increase their chances of survival (Conrad et al, 2011; Jacoby et al, 2014).


The researchers also investigated whether this sociability was consistent in different contexts, by looking at the size of groups the catsharks rested in when they were in a different kinds of habitats. They found that in simple areas, with just gravel on the ground, the sharks formed a small number of large groups, but in more three-dimensionally complex structures, like coral reefs, the sharks formed many, small groups (Jacoby et al, 2014).


Some less spotted catsharks are more social that others (Image Credit: Susana Martins, with permission)

This suggests that, whilst individual sharks differed in their sociability, the environment also had an impact on their behaviour. This is called "plasticity"; meaning that an animal is able to adapt based on the context to ensure its behaviour is not sub-optimal in different situations (Jacoby et al, 2014).


Imagine how lively you are in different situations- In a social situation, with lots of friends you know, you might be very active, loud and laugh a lot, but if you were in a situation where you and the same friends were taking a test in an exam hall, your behaviour would be very different. This does not mean your personality has actually changed, but that the context you find yourself in affects how you behave.


The catsharks adapt their behaviour in this way because, in a more complex habitat, they are less vulnerable to predators, but in a simpler habit, they are much more exposed. In this situation, they form large groups for safety via the "predator confusion effect". Their spotted skin provides them camouflage when they are in a group because it is more difficult for a predator to pick out an individual within the school. In a habit with more structure, which already offers them some camouflage, the catsharks were able to relax in their favoured small cliques (Jacoby et al, 2014).



To learn more about personality in sharks, you can check out: To Boldly Go and Fortune Favours the Brave.


References

Conrad JL, Weinersmith KL, Brodin T, Saltz JB & Sih A (2011). Behavioural syndromes in fishes: a review with implications for ecology and fisheries management. Journal of Fish Biology, 78, 395-435.


Jacoby DMP, Fear LN, Sims DW & Croft DP (2014). Shark personalities? Repeatability of social network traits in a widely distributed predatory fish. Behavioral Ecology and Sociobiology, 12:68, 1995-2003. Access online.


Acknowledgements

Thank you to Susana Martins for allowing the use of her beautiful photography in this article.



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