When a joey brush-tailed rock wallaby started peeking out from his mother’s pouch at Taronga Zoo in Sydney, keepers and visitors were pretty surprised.
That’s because Mica had given birth more than a year after the father of her joey – Sam, the zoo’s only resident male – left to go to another wildlife park. FYI, wallabies are normally born after a period of around only 28 days.
Apparently this birth delay is the result of a phenomenon known as embryonic diapause. This enables certain mammals to extend their gestation period, meaning they can time the birth of their young.
“We weren’t planning for another joey, so it was quite a shock when we started seeing something moving inside the pouch,” keeper Tony Britt-Lewis said.
The reproductive strategy is also used by kangaroos and wombats too.
“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,” Britt-Lewis said.
Britt-Lewis said keepers don’t know the joey’s sex yet. But it appears to be very healthy and about six months of age.
“Mica is a confident and attentive mum and her joey looks to be very strong. It shouldn’t be long before we start to see it venturing out of the pouch to take its first wobbly steps,” he said.
Brush-tailed rock wallabies used to live all over the rocky country of south-eastern Australia. However, they’re now listed as an endangered species in New South Wales.