VIGILANCE AND GROUPING IN THE EASTERN GRAY KANGAROO, MACROPUS-GIGANTEUS

Group formation may help animals reduce their risk of predation and al low more time for activities other than vigilance against predators. E astern grey kangaroos, Macropus giganteus, are gregarious and form ope n-membership groups. Vigilance behaviour of free-ranging kangaroos was observed in relation-to number of individuals within the group, sex a nd reproductive status of individuals, proximity to cover and position within the group. Our data support the view that kangaroos adjust the ir behaviour in relation to the risk of predation. Reproductive female s, individuals on the periphery of the group and individuals in groups far from cover were most vigilant. Contrary to previous reports, vigi lance behaviour was not influenced by group size except through the ed ge effect-the tendency of the proportion of individuals on the periphe ry of the group to decline as group size increases.