Please contact the authors if you would like a copy of the paper.
Oliver H.P. Burman, Alexander Ilyat, Gareth Jones and Michael Mendla
Ultrasonic vocalizations as indicators of welfare for laboratory rats (Rattus
norvegicus)
Applied Animal Behaviour Science
Volume 104, Issues 1-2 , April 2007, Pages 116-129
aDivision of Animal Health and Husbandry, Department of Clinical Veterinary
Science, University of Bristol, Langford House, Langford BS40 5DU, UK
bSchool of Biological Sciences, University of Bristol, Woodland Road, Bristol
BS8 1UG, UK
Abstract
Adult laboratory rats produce two distinct types of ultrasonic vocalization
(USV) that appear to reflect the caller's emotional state, either positive (50
kHz) or negative (22 kHz). If these calls can influence the emotional state and
related behaviour of group-mates, then such calls may act as useful indicators
of welfare for not only the vocalizing rat, but also other non-vocalizing
individuals within auditory range. We therefore investigated the effect of
playing back these different USVs on the behaviour of rats in an emergence
test, a test of anxiety. In an initial experiment, we compared the response of
20 rats to playback of either background noise or to playbacks of 22 kHz
vocalizations from conspecifics. Rats that received playback of the 22 kHz USVs
were less likely to emerge, showed an increased latency to emerge and spent
less total time in the open arena than rats receiving playback of background
noise, suggesting a state of increased anxiety. In a second
experiment, the same 20 rats received playback of either background noise or
50 kHz vocalizations from conspecifics. Rats receiving 50 kHz USV playback
showed no difference in emergence behaviour to those rats receiving background
noise. Taken together, these results suggest that 22 kHz USVs can induce a
negative emotional state of increased anxiety in rats hearing the vocalization,
and could therefore be a useful indicator of welfare for rat groups; including
both callers and non-calling group-mates.
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