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Camouflage can be achieved by both morphological (e.g. colour, brightness and pattern change) and behavioural (e.g. substrate preference) means. Much of the research on behavioural background matching has been conducted on species with fixed coloration and body patterns, while less is known about the role background choice plays in species capable of rapid (within minutes or seconds) colour change. One candidate species is the rock goby, Gobius paganellus , a common rock pool fish capable of rapid changes in colour and brightness when placed on different backgrounds. However, their ability to match different backgrounds is not unbounded, with some colours and brightness being easier to match than others, thus raising the possibility that gobies may use behavioural background matching to make up for their limited ability to match certain backgrounds. We used digital image analysis and a model of predator vision to investigate the ability of rock gobies to match chromatic (beige and greenish-grey) and achromatic (varying brightness) backgrounds. We then conducted choice experiments to determine whether gobies exhibited a behavioural preference for the backgrounds they were best at matching. Gobies rapidly changed their colour and brightness when placed on the different backgrounds. However, the level of camouflage differed between backgrounds: fish were better at matching beige than greenish-grey, and darker than lighter backgrounds. When given the choice, gobies displayed a behavioural preference for the backgrounds they were best at matching. Our findings therefore show that rock gobies, and probably other animals, use a combination of morphological and behavioural means to achieve camouflage and in doing so mitigate limitations in either approach alone. Highlights • Gobies rapidly change colour and luminance in response to their background. • Fish were better at matching the colour beige than greenish-grey. • Gobies are much better at matching dark backgrounds than brighter ones. • Gobies show a behavioural preference for the background they are best at matching. • A mixture of behaviour and colour change probably helps mitigate limitations in both. [ABSTRACT FROM AUTHOR]

Animal ‘personality’, the phenomenon of consistent individual differences in behaviour within populations, has been documented widely, yet its functional significance and the reasons for its persistence remain unclear. One possibility is that among-individual behavioural variation is linked to fitness-determining traits via effects on resource acquisition. In this study, we tested this idea, using rockpool prawns, Palaemon elegans , to test for a correlation between ‘high-risk exploration’ and the ability to monopolize a limited resource. Modified open field trials (OFTs) confirmed that consistent among-individual (co)variation in high-risk exploratory behaviours does exist in this species, and multivariate analysis showed trait variation is consistent with a major axis of personality variation. Subsequent feeding trials in size-matched groups where competition was possible revealed a high repeatability of feeding duration, used here as a proxy for RHP (resource-holding potential). We found significant negative correlations between feeding duration and two ‘risky’ behaviours, such that individuals that took fewer risks fed more. Our results are not consistent with the widely hypothesized idea of a ‘proactive syndrome’ in which bolder, risk-taking personalities are positively associated with RHP. Rather they suggest the possibility of a trade-off, with some individuals successful at monopolizing limited, high-value resources, while others are more willing to engage in potentially risky exploration (which may increase the likelihood of encountering novel resource patches). We speculate that alternative strategies for acquiring limited resources might thereby contribute to the maintenance of personality variation observed in wild populations. [ABSTRACT FROM AUTHOR]

Cognition is vital for carrying out behaviours required for survival and reproduction. Cognitive performance varies between species, but also between individuals within populations. While variation is a prerequisite for natural selection, selection does not act on traits in isolation. The extent to which cognitive traits covary with other aspects of phenotype (e.g. personality traits) may be important in shaping evolutionary dynamics. Here we adopted a multivariate approach to test spatial learning in male Poecilia reticulata and asked whether differences in cognitive performance are associated with (repeatable) differences in stress response behaviour. Functional links between cognitive traits and 'stress coping style' have been hypothesized. Furthermore, individual level studies of cognitive performance typically rely on multiple testing paradigms that may themselves be a stressor. There is a risk that variation in stress responsiveness is itself a cause of apparent, but artefactual variance in cognitive ability. Fish repeatedly experienced two spatial learning tasks (maze layouts) and an acute stress response test (open field trial). We found repeatable differences between individuals in performance within and across maze layouts. On average, performance improved with experience in the first maze, consistent with spatial learning, but not in the second. Individuals varied in the trajectory of mean performance with trial number in both mazes, suggesting they differ in 'learning rate'. Acute stress response behaviour was repeatable but predicted neither average time to solve the maze nor learning rate. We found no support for between-individual correlation between acute stress response and cognitive performance. However, we highlight the possibility that cumulative, chronic stress effects may nevertheless cause declines in performance for some individuals (leading to lack of improvement in mean time to solve the second maze). If so, this may represent a pervasive but difficult challenge for our ability to robustly estimate learning rates in studies of animal cognition. • Multivariate approach to test spatial learning and acute stress response in guppies. • Spatial learning performance is repeatable among individuals across contexts. • Acute stress response behaviour is also repeatable among individuals. • No support for correlation between acute stress response and cognitive performance. • Cumulative chronic stress may cause declines in performance for some individuals. [ABSTRACT FROM AUTHOR]