Taxonomy and distribution of the grey kangaroos, Macropus giganteus Shaw and Macropus Fuliginosus (Desmarest), and their subspecies (Marsupialia : Macropodidae)

Abstract

Of all the Macropodidae, grey kangaroos cover the widest range in Australia. There is considerable geographical variation in morphology and opinions have differed as to the taxonomic status of the various kinds. This investigation supports a primary division of grey kangaroos into two species-eastern and western on the basis of serological, reproductive, and morphological distinctions. The eastern species, M. giganteus, is found in all eastern states, Queensland, New South Wales, Victoria, and Tasmania, plus south-east South Australia, while the western species, M. fuliginosus, occurs in south-western Western Australia and southern South Australia including Kangaroo I., extending into western Victoria and south-western New South Wales, where the ranges of the two species overlap. Transferrin polymorphism was detected by starch-gel electrophoresis, revealing three phenotypes, A, AB, and B. Western populations possess all three phenotypes, but eastern populations have type A only. Western and eastern grey kangaroos also have characteristic antigens. Eastern animals when immunized with sera from western kangaroos produced antibodies which during double-diffusion analysis reacted with sera from western individuals. Likewise the reverse immunization acted as expected. Thus the origin of individuals, from western or eastern populations, could be determined. Hybrids were not found in the field, but matings between captive western males and eastern females the reverse mating never occurred produced hybrids whose antigens were characteristic of both parental types. In eastern grey kangaroos the mean length of oestrous'cycle, 45.6 days, and gestation period, 36.4 days, is longer than in western kangaroos, with mean lengths 34.9 and 30.6 days. Oestrous cycles of hybrid females and gestation periods of all hybrids are of intermediate length, 37.6 and 34.1 days respectively. The colour of eastern grey kangaroos ranges from light to dark grey while western kangaroos are brown. The history of the previously described taxa and the effect of the current findings on the nomenclature relating to grey kangaroos are discussed.