Delighted visitors at Sydney’s Taronga Zoo have been treated with the appearance of a joey peeking out of its mother Mica’s pouch this month – somewhat to the surprise of keepers, given the only resident male left the zoo more than a year ago.
“We weren’t planning for another joey, so it was quite a shock when we started seeing something moving inside the pouch,” said Tony Britt-Lewis, a Keeper at the zoo.
The unexpected birth is the result of a phenomenon called ’embryonic diapause’, which enables certain mammals to extend their gestation period and time the birth of their young. “It’s an interesting survival mechanism that allows the mother to delay the development of the embryo in drought conditions or if she already has a joey in the pouch,” explained Tony.
Mum, Mica – a brush-tailed rock wallaby (Petrogale penicillata) – was carrying another joey in her pouch until August last year, about five months after the only resident male, Sam, had moved to another wildlife park. Zoo keepers suspect Mica mated with Sam soon after giving birth to her previous joey, and the resulting embryo stayed dormant while her pouch was occupied.
IMAGE CREDIT: Paul Fahy
According to a statement released by Taronga Zoo, the new joey looks to be about six months old, and its sex is yet to be determined.
Brush-tailed rock wallabies are listed as an endangered specied in NSW. They were hunted extensively for their fur in the 1900s and continue to be threatened by habitat loss and introduced predators such as foxes and cats.
This story originally appeared on Australian Geographic.
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