Plastic proteans: reduced predictability in the face of predation risk in hermit crabs

Abstract

Variation in behaviour occurs at multiple levels, including between individuals (personality) and between situations ( plasticity). Behaviour also varies within individuals, and intra-individual variation (IIV) in behaviour describes within-individual residual variance in behaviour that remains after the effects of obvious external and internal influences on behaviour have been accounted for. IIV thus describes how predictable an individual's behaviour is. Differences in predictability, between individuals and between situations, might be biologically significant. For example, behaving unpredictably under predation threat might reduce the chance of capture. Here, we investigated the duration of startle responses in hermit crabs, in the presence and absence of a predator cue. Individuals differed in startle response duration ( personality) and while individuals also varied in their sensitivity to risk, mean response time was greater in the presence of a predator ( plasticity). Moreover, IIV was greater in the presence of a predator, providing some of the first evidence that the facultative injection of unpredictability into behaviour might represent a strategy for dealing with risk.

Individual quality and personality: bolder males are less fecund in the hermit crabPagurus bernhardus

“…We also found, similar to previous studies, that crab mass had no effect on the mean duration of startle responses [44]. Although we have controlled for mass in previous analyses of IIV [3,8,9], this is the first time that we have tested the 46], the size range of crabs used in this study represents only a small proportion of the size and hence age range of sexually mature males. Thus, ontogenetic variation is unlikely to underpin this trend for increasing unpredictability with crab mass.…”

“…Long startle responses reduce the time available for other activities, but provide a mechanism for avoiding risk. Thus, in hermit crabs, startle responses increase in duration under conditions of high risk [9,44,51]. Similar positive associations between risk level and hiding time are also seen in other species (e.g.…”

“…Previous studies indicate that IIV in hermit crab hiding times varies with ambient risk level [3,9]. We suggested that rspb.royalsocietypublishing.org Proc.…”

Individual variation in avian avoidance behaviours in response to repeated, simulated vehicle approach

“…Individual personality also can contribute to how animals respond to risk (Sih et al 2015), and variation across individuals might result from high individual repeatability in behaviours over time (Carrete and Tella 2010, 2013Briffa 2013;Highcock and Carter 2014). Within-individual variability reflects the predictability or repeatability of an animal's behaviour (Briffa 2013).…”

“…Within-individual variability reflects the predictability or repeatability of an animal's behaviour (Briffa 2013). For example, Carrete and Tella (2010) found that breeding Burrowing Owls (Athene cunicularia (Molina, 1782)) exhibited relatively high repeatability (0.84-0.92; low within-individual variation) in flight initiation distance (FID) in response to human approaches toward burrows, and speculated that selection and distribution of breeding sites reflected different levels of individual tolerance to human disturbance.…”