Lemon sharks – live fast, die young

News Release

Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB)

29. July 2020

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Risk-taking individuals are expected to grow better but also die faster than the less explorative individuals. Such trade-offs can maintain multiple phenotypes in a population by allowing individuals with different behavioural strategies to achieve comparable fitness, according to the hypothesis that IGB together with an international team has thus tested – and could not substantiate for every ecological context.

An international team around Félicie Dhellemmes from IGB investigated the behaviour and life-history of lemon sharks in the Bahamas. The team could show: Lemon sharks exhibit consistent individual differences in behaviour – they have a personality. And this personality can, under certain circumstances, determine the course of life. The researchers studied two shark populations, first in semi-captivity and then in the wild, where the two groups were exposed to different environmental conditions; in one area there were few larger sharks that can threaten the juvenile lemon sharks as predators, in the other area there were more predators. The more explorative sharks in captivity took more risks in the wild and grew faster. In turn, larger, fast-growing sharks had lower apparent survival. It is still unclear why this only applied to one of the two shark populations studied by the team. In the other group with a higher predator pressure, fast-growing sharks were also more likely to die, but this was not linked to personality and risk-taking behaviour. “In a predator-rich environment, sharks may not fully behave according to their personality, making the evidence of a link to life history impossible to detect ”, says IGB researcher Félicie Dhellemmes, first author of the study.

Life as a compromise

Researchers explain differences in personality with the pace-of-life-syndrome hypothesis, which gives an evolutionary explanation for the maintenance of phenotypic variation within populations. This theory says that there is a link between life-history and personality. Life-history trade-offs occur when the optimal response for one trait is reached at the expense of another. Such trade-offs can maintain multiple phenotypes in a population by allowing individuals with different behavioural strategies to achieve comparable Fitness –  that is, securing the offspring. For example, fast growth might be reached at the expense of survival, when the additional foraging effort is associated with decreased vigilance towards potential predators. Fast-growing individuals might then reach sexual maturity faster, increasing their fitness but they might also die sooner than slow growing individuals, resulting in equivalent fitness.

“Empirical support for the pace-of-life-syndrome hypothesis remains limited and ambiguous. Our study demonstrates that the association between personality and life-history is favoured in some ecological contexts but not in others. We identify predator and resource abundance as two main potential drivers of the personality mediated trade-off”, concludes Félicie Dhellemmes.

Related scientific article: Personality‐driven life history trade‐offs differ in two subpopulations of free‐ranging predators

Source: igb-berlin

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