Breeding in the Grey Kangaroo, MAcropus giganteus, from Widespread Locations in Eastern Australia

Abstract

Small samples of eastern grey kangaroos drawn from a number of locations throughout their known distribution, and over a period of years, provided information on their breeding biology, which complemented earlier reports from restricted study areas. Irrespective of locality, young appeared to be born in all months of the year with the majority of births in the summer months, though subject to modification by seasonal conditions. Comparison of reproductive strategies adopted by red and grey kangaroos at one site under identical conditions of less than average rainfall supported an earlier theoretical proposition that the two species were subject to 'r' and 'K' selection respectively. Both male and female grey kangaroos became sexually mature from age 20 to 36 months. Quiescent blastocysts in some females suckling advanced pouch young were noted in most populations. Although apparently associated with favourable nutritional conditions, the stimuli which induce an oestrus resulting in the carrying of a quiescent blastocyst are not yet understood.