• SharkieSophie

Fortune Favours the Brave

Updated: Apr 26

When we talk about personality, we often assume it is a solely human trait. However, this is far from true! In fact, “personality” (which is defined as consistent individual differences in behaviour throughout time and in different situations) has been proven to exist in over 200 species of animals - from insects to mammals - including several species of sharks, such as the lemon shark (Negaprion brevirostris), the Port Jackson shark (Heterodontus portjacksoni), the tiger shark (Galeocerdo cuvier), the lesser spotted catshark (Scyliorhinus canicula) and the blacktip reef shark (Triaenodon obesus)... But what does this mean? What does personality look like in a shark?


Port Jackson sharks (Image credit: Michaela Skovranova, Source: www.nytimes.com)

Animal personality is assessed in terms of five personality traits: 1. activity (an animal which is sluggish versus very active), 2. aggression (whether they are placid or aggressive in social contexts), 3. willingness to explore (exploration versus avoidance), 4. boldness (as opposed to shyness) and 5. sociability (whether they are solitary or prefer a large group) (Finger et al, 2017).


Blacktip reef sharks (Image source: https://sharkright.com)

Some sharks are more bold than others…

An animal which is more bold, compared to one which is more shy, will be less cautious in a situation perceived as dangerous, like when a predator is present. Bold individuals take more risks. In a study of Port Jackson sharks, researchers used an “emergence test” to assess individual boldness; whereby they placed the shark inside a shelter and then measured how long it took to emerge out from relative safety. They found that individuals consistently differed in the time it took them to emerge; the more bold individuals emerging more quickly. Similarly, juvenile lemon sharks have been found to differ in their boldness when foraging for food within the nursery habitat (Byrnes & Brown, 2016, Finger, et al, 2017).


Researchers have suggested that boldness has evolved because it allows these individuals to reach foraging opportunities more rapidly and readily. However, this strategy is also more risky; a kind of live fast, die young strategy. A study of personality in lemon sharks found that bolder individuals were more fast-growing, but also had a higher mortality rate. Therefore, at the other end of the spectrum, less bold individuals were also able to survive because, whilst they may not have been able to exploit all foraging opportunities, they were less exposed to risky situations and had a lower mortality rate (Finger, et al, 2017).


Lemon sharks (Image credit: C.J. Crooks, Source: https://blog.nationalgeographic.org)

Some sharks are more explorative than others…

An animal which is relatively explorative will make extensive movements to orient itself in a new environment. At the opposite end of the scale, an individual that displays avoidance, will only explore a small area; they prefer to stay close to home. A study to assess explorativeness in lemon sharks, found that individuals had significant differences in their rate of movement when they were placed into a new environment. It is thought that explorative individuals and home-bodies are able to coexist because they exploit a different “ecological niche”; the explorative sharks strike out to find new foraging opportunities and leave space for others to utilise food sources closer to home (Finger et al, 2017).


Differences in explorativeness can also have implications in movements on a larger scale. Tiger sharks (Galeocerdo cuvier) studied in Hawaii have been shown to have individual differences in how explorative they are, which affects whether they migrated long-distance. This means that some individual tiger sharks were residents of a specific area, where others were only transient (Meyer et al, 2010).


Tiger shark (Image credit: By Albert Kok, Source: https://commons.wikimedia.org)

Some sharks are more sociable than others…

Sociability as a personality trait refers to an animal’s reaction to other individuals of the same species (aka “conspecifics”). Asocial individuals will avoid conspecifics and favour smaller social groups, where social individuals display an attraction towards conspecifics. Lesser spotted catsharks have been found to have social interactions with specific individuals, which remain consistent even in different habitats; like they have favourite pals. It has also been discovered that the catshark has an organised social structure and each individual’s rank within the hierarchy is consistent (Byrnes & Brown, 2016, Finger, et al, 2018).


Blacktip reef sharks and lemon sharks have also been shown to differ in how social they are, with some individuals preferring large groups, where other consistently favoured to spend time in very small groups (Finger, et al, 2017). Whatsmore, lemon sharks are commonly seen with the same conspecifics and are consistent in whether they are a ‘leader’ or a ‘follower’ in a social group (Byrnes & Brown, 2016).


Lesser spotted catsharks (Image Source: https://www.marlin.ac.uk)

Sharks have complex personalities…

What is especially cool, is that, not only have sharks been found to have personalities, but we now also know that their personalities are complex and multi-facetted. In animals it is common that a certain personality trait will always be associated with another, completely different feature; for example, an individual which is often aggressive will also often be very active or an individual which is very bold is also very explorative. This is known as a “behavioural syndrome”.

(Byrnes & Brown, 2016)

A recent study sought to investigate behavioural syndromes in the Port Jackson shark, by assessing how bold they were using an emergence test, and testing how sensitive to stress they were by measuring their activity and rate of movement when stressed (this species tends to become very active when agitated, so a shark moving more slowly is likely to be relaxed and calm). The researchers found that an individual Port Jackson shark which was consistently more bold was also less reactive when they were exposed to stress, suggesting a strong behavioural syndrome exists between these two traits (Byrnes & Brown, 2016).


It is very important to understand personality in animals because it can be critical to design management strategies for endangered species. It has been noted that bold and/or explorative individuals may be more likely to be exposed to fisheries or beach nets, which could mean that these animals are disproportionately vulnerable to extraction. Similarly, more active and/or more exploitive sharks may be more likely to undergo extensive migrations, which could make them more likely to survive if their habitat is degraded, compared to individuals which prefer to stay close to home. In several other animals it has been shown that personality traits have a genetic component, which is heritable from parent to offspring. Therefore, skewed mortality of individuals with a certain personality trait, could reduce the genetic diversity of the species as a whole. This diversity is critical for conservation because it makes the species more resilient and more likely to survive.


To learn more about shark personality, you can check out my articles: To Boldly Go and A Small Shark with a Big Personality.

References

Byrnes EE & Brown C (2016). Individual personality differences in Port Jackson sharks Heterodontus portjacksoni. Journal of Fish Biology, DOI:10.1111/jfb.12993. Access online.


Byrnes EE, Pouca CV & Brown C (2016). Laterality strength is linked to stress reactivity in Port Jackson sharks (Heterodontus portusjacksoni). Behavioural Brain Research, 305, 239-246. Access online.


Finger JS, Dhellemmes F & Guttridge TL (2017). Personality in elasmobranchs with a focus on sharks: early evidence, challenges, and future directions. In: Vonk, J., Weiss, A. & Kaczaj, S.A. (Eds.). Personality in Nonhuman Animals, 129-152. Springer, Berlin.


Finger JS, Guttridge TL, Wilson ADM, Gruber SH, & Krause J (2018). Are some sharks more social than others? Short- and long-term consistencies in the social behaviour of juvenile lemon sharks. Behavioural Ecology and Sociobiology, 72:17, DOI: 10.1007/s00265-017-2431-0.


Meyer CG, Papastamatiou YP & Holland KN (2010). A multiple instrument approach to quantifying the movement patterns and habitat use of tiger (Galeocerdo cuvier) and Galapagos sharks (Carcharhinus galapagensis) at French Frigate Shoals, Hawaii. Marine Biology, 157, 1857–1868. Access online.


By Sophie A. Maycock for SharkSpeak.

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