Variation in response to environmental cues when foraging

• Main Author: Herborn, Katherine
• Published: University of Glasgow 2010
• Subjects: 591.5; QL Zoology
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.524022

Animals often respond differently to the same environmental cues. Where behavioural responses differ consistently between individuals over time or contexts, this is “personality”. In wild animals, personality is linked to variation in fitness and survival. Predictions on the behavioural mechanisms underlying this variation come from captive studies, on the often untested assumption 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 predicted foraging behaviour in the wild. I measured the personality traits neophobia (latency to feed in novel scenarios) and exploratory tendency, first by relatively standard captive protocols and second, using an electronic monitoring system at feeding stations, by novel wild methods. As predicted, analogous traits correlated across contexts. Moreover, neophobia and exploratory tendency 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 whilst neophilic and exploratory types maintain foraging routines. In chapter 3, I tested this second captive prediction in the wild, defining environmental sensitivity in the wild by changes in feeder use with varying air temperature or food supply. Neophobic and, contrary to expectation, exploratory blue tits were most environmentally sensitive. By contrast, neophilic and nonexploratory birds visited feeders at a fixed level independent of temperature and continued to visit feeders for a prolonged period even after they were emptied. Age and body size also influenced environmental sensitivity, suggesting learning and dominance interactions modify the expression of personality in the wild. From potential behavioural costs, in chapter 4 I turned to the physiological costs of personality. Variation in metabolic rate and stress metabolism may be proximate mechanisms for personality. Whilst these physiological traits are linked to oxidative stress directly, with pro-oxidants that damage body tissue a by-product of metabolism, few studies 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-bred greenfinches (Carduelis chloris). Finally, variation in response to environmental cues may reflect differences in learning between individuals, as perhaps illustrated by age differences in environmental sensitivity (Chapter 3). In chapters 5 and 6, I investigated whether learning that a feeding site is temporally stable could cause changes in response to food appearance (“local cues”) when foraging. I predicted that birds would re-find food by spatial rather than local cues in these scenarios, as appearance can change hence local cues become unreliable over time. In chapter 5, I carried out an associative learning test to test this prediction in captive-bred greenfinches. Within a simple foraging scenario, the prediction was upheld: greenfinches favoured local cues in situations where the temporal stability of food was unknown, but switched to spatial cues when temporal stability was learnt through repeated encounters. In chapter 6 though, four of five wild bird species foraging at temporally stable bird feeders continued to respond to local cues, selecting feeders on the basis of colour. Most species were biased toward red feeders, and also responded to social cues when finding feeders: foraging strategies better suited to finding ephemeral food than re-finding temporally stable feeding sites. I suggest that wild birds use information on temporal stability from the broader environment (i.e. natural ephemeral food beyond temporally stable artificial feeders). This illustrates how animals may not necessarily forage in the wild as we would expect within specific contexts. Throughout this thesis therefore, my findings illustrate the importance of testing predictions generated from captive behaviour in the wild. Moreover, identifying variation in both the foraging strategies and physiological costs to individual variation in behaviour, this thesis provides new insight into the adaptive significance of animal personality.