One of Australia's oldest known animals, the musky rat-kangaroo, is the subject of a University of Queensland study which may shed light on links between kangaroos and possums.
Researcher Shan Lloyd, who is studying the musky rat-kangaroo for her PhD in anatomical sciences, said little was known about the life and reproductive cycle of the diminutive marsupial.
Ms Lloyd is conducting field studies of seven musky rat-kangaroo populations near Atherton and Mission Beach in Queensland's Wet Tropics region as well as undertaking a captive breeding program at the University's veterinary science farm at Pinjarra Hills in Brisbane.
'The musky rat-kangaroo is the most primitive of the kangaroos and while it is not considered endangered, it is rare because its rainforest habitat is rare and fragmented,' Ms Lloyd said.
'We think the musky rat-kangaroo is the closest living relative to the ancestral phalangerid (possum) from which kangaroos evolved. There are many similarities to the possum: the musky rat-kangaroo doesn't bound like a kangaroo, it scurries; it has an extra digit on its back feet, a simple, monosaculated stomach, is a fruit eater, and has possum-like dental characteristics.'
Ms Lloyd's research is focusing on breeding patterns and genetic differences between populations in different areas.
'We would like to see how sperm production differs in musky rat-kangaroos, possums and kangaroos, and record basic information about the female's oestrus cycle and gestation period,' she said.
'We have very little knowledge of the musky rat-kangaroo's reproductive cycles. For example, the males' testes shrink in winter but are huge in summer. In a kangaroo, testes account for about 0.5 percent of its body weight, and in the musky rat-kangaroo they account for 4 percent of body weight in summer.
'We assume they are not reproductively active in winter, because it looks like they shut down and don't make sperm, but that might not be true. Our knowledge of reproduction is not great enough to say why, but it could be because of poor body condition.'
Current research suggests that about 66 per cent of the musky rat-kangaroo population is male, but Ms Lloyd said this could be because males are more easily trapped for some reason.
Breeding starts at about 18 months and a female has only about three breeding seasons in its average four year life span. Twins and triplets are usual.
Genetic research will investigate differences between populations in different areas to try to determine the impact of the Black Mountain barrier, west of Cairns, in which pockets of rainforest were separated on either side during glacial periods.
'Morphologically there is no difference between populations, but unless the musky-rat kangaroo was restricted to one side of the barrier, re-dispersing after the glacial periods, then there must be some genetic differences.'
For more information, contact Ms Lloyd (telephone (07) 3202 6967).
