Summary: h i m . Behav., 1984,32,1108-1118
BEHAVIOURAL VARIATION IN NATURAL POPULATIONS. III:
ANTIPREDATOR DISPLAYS IN THE GARTER SNAKE
BY STEVAN J. ARNOLD*$ & ALBERT F. BENNETT1
*Department of Biomathematics, University of Oxford, Oxford, OX1 WZ, U.K.
fSchool of Biological Sciences, University of Calfomia, Irvine, CA 92717, U.S.A.
Abstract. Recently born garter snakes (Thamnophis radix) were subjected to a variety of threatening
stimuli. They would crawl away from the investigator until high levels of lactate were attained, and then
adopt one of a variety of antipredator displays. These antipredator behaviours were surprisingly vari-
able between individuals of a single population, but behaviours of individuals were consistent in repli-
cate trials and in response to different stimuli. Snakes became more defensive when simulated predator
attacks were more severe, but they became more offensive when tested at a lower temperature. Analysis
of behavioural variation within and between 15 litters of full-sibling (172) snakes gave heritability esti-
mates of 0.37 for single trials and 0.45 for the average of two replicate trials. This is the &st study to
examine the heritability of antipredator behaviour in any terrestrial vertebrate species.
Behaviourists have neglected the study of
behavioural variation in natural populations.
Because we know so little about the raw material