Heavier birds react faster to predators: individual differences in the detection of stalking and ambush predators |
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Authors: | Katherine A Jones John R Krebs Mark J Whittingham |
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Institution: | (1) Department of Ecology and Evolutionary Biology, Faculty of Biomedical and Life Sciences, University of Glasgow, Graham Kerr Building, Glasgow, G12 8QQ, UK;(2) Department of Zoology, Edward Grey Institute of Field Ornithology, Oxford University, South Parks Road, Oxford, OX1 3PS, UK;(3) School of Biology and Psychology, Newcastle University, Ridley Building, Newcastle-Upon-Tyne, NE1 7RU, UK |
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Abstract: | The relationship between body mass and reactions speed in response to a predatory threat is poorly understood. Theory predicts
that different vigilance patterns are optimal for the detection of different predator types. We suggest that birds of different
individual state might also differ in their speed of response dependent upon predator type. We used laboratory trials of wild
caught chaffinches (Fringilla coelebs) to determine how between individual differences in chaffinch behaviour and state correlate with latency to react to a ground
predator model (domestic cat), thus providing a comparison with previous work in the same model system using aerial predator
models. In experiment 1, we observed chaffinch responses to a moving cat model, simulating a stalking predator. In experiment
2, we used a camouflaged cat model simulating an ambush predator. Both experiments show evidence suggesting heavier individuals
(which previous literature has linked to impaired flight performance) responded more quickly to the model cat. Heavier individuals
also had shorter interscan intervals. In contrast to a previous study, both experiments found individuals with a higher intake
rate were not faster at responding to the cat model. In addition, individuals in experiment 1 that head turned more while
scanning were slower to respond to the stalking cat model. Our work suggests that although heavier individuals may have impaired escape performance
they appear to show behavioural compensation by allocating more attention to anti-predator behaviour and by modifying their
interscan intervals, resulting in faster response times to a ground predator. We suggest more experiments investigating response
time to different predatory types and explicitly manipulating state to elucidate cause and effect. |
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Keywords: | Anti-predator behaviour Reaction speed Predation Stalking Vigilance Body mass |
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