Abstract
Marine environments are subject to increasing disturbance events, and coral reef ecosystems are particularly vulnerable. During periods of environmental change, organisms respond initially through rapid behavioural modifications. Whilst mean population level modifications to behaviour are well documented, how these shifts vary between individuals, and the relative trade-offs that are induced, are unknown. We test whether the frequency and time invested in different behaviours varies both between and within individuals with varying resource availability. To do this, we quantify differences in four key behavioural categories (aggression, exploration, feeding and sociability) at two sites of different resource availability, using an obligate corallivore butterflyfish species (Chaetodon lunulatus). Individuals on a low resource site held larger territories, investing more time in exploration, which was traded off with less time invested on aggression, feeding and sociability. Repeatability measures indicated that behavioural differences between sites could plausibly be driven by both plasticity of behaviour within individuals and habitat patchiness within feeding territories. By combining population-level means, co-correlation of different behaviours and individual-level analyses, we reveal potential mechanisms behind behavioural variation in C. lunulatus due to differences in resource availability.Significance statementUsing observational methods, we identify differences in the behaviour of an obligate corallivorous butterflyfish (Chaetodon lunulatus) between a high and a low resource site. We use a combination of density surveys, territory mapping and behavioural observation methods in a comparative analysis to relate behaviour directly to the environment in which it occurs. Bringing together insights from game theory and optimal foraging, we also use our results to highlight how understanding the correlations of different behaviours can inform our understanding of the extent to which behaviours are plastic or fixed. Furthermore, by considering how multiple behaviours are correlated, we move away from exploring individual behaviours in isolation and provide an in-depth insight into how differences in behaviour both between individuals and at the population level can affect responses to declining resource availability.
Highlights
Behaviour mediates an organism’s complex interactions with both its biotic and abiotic environment
To visualise correlations of behaviours of individual pairs, we used a principal component analysis (PCA) with the Kaiser–Meyer–Olkin (KMO) criterion as a measure of sampling accuracy (Kaiser and Rice 1974) and Bartlett’s test of sphericity (Bartlett 1951) to ensure our data fit the assumptions of PCA
The proportion of variance from the ANOVAs attributed to both within and between individual variations was similar between the two sites, with the exception of feeding, where between individual variation accounted for 70% of total variance at the. We have identified both broad and fine scale differences in the behaviour of C. lunulatus between two sites of different resource availabilities
Summary
Behaviour mediates an organism’s complex interactions with both its biotic and abiotic environment. Spatial and temporal variation in the environment can affect various aspects of behaviour, such as predation and competition, which in turn can alter species interactions (Anholt 1997). Changes in behaviour have the potential to shape ecological communities (Delarue et al 2015). The capacity for a population to acclimate and/or adapt behaviourally to severe environmental change can be determined by factors such as if and how behaviour is transmitted between individuals (Keith and Bull 2017), geographic variation in biotic interactions (Early and Keith 2018) and the likelihood that initial acclimation contributes to evolutionary or ecological traps (Schlaepfer et al 2002). Individual behaviour can, scale up to influence population dynamics, with broader community and ecosystem-level consequences (Wong and Candolin 2015). To understand any potential mechanisms or limitations on adaptation, there is a need to understand the role of individual variation and associated trade-offs in responses to environmental change
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