Volume 75, Issue 1, January 2008, Pages 299–307
·
Barbara Clucas*, , ,
·
Matthew P. Rowe†, 2,
·
Donald H. Owings*, ‡, 1,
·
* Animal Behavior Graduate Group,
University of California, Davis, U.S.A.
·
† Department of Biological Sciences, Sam
Houston State University, U.S.A.
·
‡ Department of Psychology, University of
California, Davis, U.S.A.
·
§ Department of Fishery and Wildlife
Science, New Mexico State University, Las Cruces, U.S.A.
Chemical substances produced by one species are
sometimes found on the body of another species. Animals often ingest such
foreign substances and sequester them into their integument, but here we report
a case of direct application of heterospecific substances to the body.
California ground squirrels, Spermophilus beecheyi, and rock squirrels,
Spermophilus variegatus, apply scent derived from their major predator,
rattlesnakes, Crotalus spp., by chewing shed rattlesnake skins and licking
their fur. We found that the sequence of body areas licked during application
was essentially the same for the two species. We consider three hypotheses
regarding the function of this ‘snake scent application’ (SSA): antipredator
defence, ectoparasite defence, and conspecific deterrence. To test these
hypotheses, we assessed patterns of species and sex/age class differences in
application quantity and compared them with patterns reflecting differences in
the importance of predation, flea loads and conspecific aggression as sources
of selection. We found no species differences in application quantity; however,
juveniles and adult females of both species engaged in longer bouts of
application than adult males. This pattern of sex/age class differences in SSA
supports only the antipredator hypothesis because juveniles are most vulnerable
to predation and adult females actively protect their young. We found no
evidence to support either the ectoparasite defence or conspecific deterrence
hypotheses. Thus, SSA behaviour may be a novel form of chemical defence against
predation.
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