Variation in response to environmental cues when foraging

QL Zoology

Herborn, Katherine ; Arnold, Kathryn

University:University of Glasgow

关键词: Personality, cue selection, oxidative stress, behavioural syndromes, exploration, neophobia, Cyanistes caeruleus, Carduelis chloris;   

Others  :  http://theses.gla.ac.uk/2159/1/2010herbornphd.pdf

来源: University of Glasgow

【 摘 要 】

Animals often respond differently to the same environmental cues. Where behavioural responsesdiffer consistently between individuals over time or contexts, this is “personality”. In wildanimals, personality is linked to variation in fitness and survival. Predictions on the behaviouralmechanisms underlying this variation come from captive studies, on the often untestedassumption that captive behaviour reveals how animals would behave in the wild. In chapter 2,using blue tits (Cyanistes caeruleus) I tested first whether behaviour in captivity predictedforaging behaviour in the wild. I measured the personality traits neophobia (latency to feed innovel scenarios) and exploratory tendency, first by relatively standard captive protocols andsecond, using an electronic monitoring system at feeding stations, by novel wild methods. Aspredicted, analogous traits correlated across contexts. Moreover, neophobia and exploratorytendency were uncorrelated within individuals in both contexts, in contrast to many other species.In captive studies, personality types also respond differently to changing environmental cues, or“environmental sensitivity”: neophobic and non-exploratory types adjust behaviour whilstneophilic and exploratory types maintain foraging routines. In chapter 3, I tested this secondcaptive prediction in the wild, defining environmental sensitivity in the wild by changes in feederuse with varying air temperature or food supply. Neophobic and, contrary to expectation,exploratory blue tits were most environmentally sensitive. By contrast, neophilic and nonexploratorybirds visited feeders at a fixed level independent of temperature and continued to visitfeeders for a prolonged period even after they were emptied. Age and body size also influencedenvironmental sensitivity, suggesting learning and dominance interactions modify the expressionof personality in the wild. From potential behavioural costs, in chapter 4 I turned to thephysiological costs of personality. Variation in metabolic rate and stress metabolism may beproximate mechanisms for personality. Whilst these physiological traits are linked to oxidativestress directly, with pro-oxidants that damage body tissue a by-product of metabolism, fewstudies link personality to oxidative stress. I found that oxidative profile (pro-oxidants,antioxidants, oxidative stress and oxidative damage) and hence physiological costs differed notonly within traits but also related differently to neophobia and object exploration in captive-bredgreenfinches (Carduelis chloris). Finally, variation in response to environmental cues may reflectdifferences in learning between individuals, as perhaps illustrated by age differences inenvironmental sensitivity (Chapter 3). In chapters 5 and 6, I investigated whether learning that afeeding site is temporally stable could cause changes in response to food appearance (“localcues”) when foraging. I predicted that birds would re-find food by spatial rather than local cues inthese scenarios, as appearance can change hence local cues become unreliable over time. Inchapter 5, I carried out an associative learning test to test this prediction in captive-bredgreenfinches. Within a simple foraging scenario, the prediction was upheld: greenfinchesfavoured local cues in situations where the temporal stability of food was unknown, but switchedto spatial cues when temporal stability was learnt through repeated encounters. In chapter 6though, four of five wild bird species foraging at temporally stable bird feeders continued torespond to local cues, selecting feeders on the basis of colour. Most species were biased towardred feeders, and also responded to social cues when finding feeders: foraging strategies bettersuited to finding ephemeral food than re-finding temporally stable feeding sites. I suggest thatwild birds use information on temporal stability from the broader environment (i.e. naturalephemeral food beyond temporally stable artificial feeders). This illustrates how animals may notnecessarily forage in the wild as we would expect within specific contexts. Throughout this thesistherefore, my findings illustrate the importance of testing predictions generated from captivebehaviour in the wild. Moreover, identifying variation in both the foraging strategies andphysiological costs to individual variation in behaviour, this thesis provides new insight into theadaptive significance of animal personality.