Physiological response of the European hedgehog to predator and nonpredator odour.

A respiratory chamber was used to investigate physiological responses of hedgehogs to predator and nonpredator odour cues, introduced by passing air through different faecal suspensions. Five recently caught hedgehogs showed a significant increase in oxygen consumption (29% +/- 18% at 95% c.i.) when treated with badger (predator) faecal suspension, and 10 hedgehogs held in captivity for ca. 2 years showed no significant response. The responses of recently caught hedgehogs to odour from badger (predator) and roe deer (non-predator) faecal suspensions were then investigated, over a range of concentrations spanning 3 orders of magnitude. Five hedgehogs were tested with badger odour; of these, 3 were also tested with roe deer odour. The mean rise in oxygen consumption was significantly greater in response to badger than to roe deer faecal suspension, but there was no significant variation in strength of response over the range of concentrations tested, and increased oxygen consumption was not associated with any increase in levels of visible activity. The responses are interpreted as an increase in arousal in response to a potential predatory threat. Lack of response in the captive-held animals raises questions about the welfare of such animals following release. Energy costs and foraging inefficiency associated with arousal may be significant factors of foraging decisions involving predation risk, but more naturalistic measurements would be required for any quantitative analysis.