This Marsupial is the Only Animal That's Always Pregnant
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This marsupial is the only animal that's always pregnant
Most mammals can become pregnant several times during adulthood, but for the vast majority, there is a healthy pause after each birth, while mothers nurse their babies. For some, of course, it's normal to only have one or a couple offspring in a lifetime.
But swamp wallabies, small hopping marsupials found throughout eastern Australia, are far outside the norm: New research suggests that most adult females are always pregnant. As described in a paper published March 2 in the Proceedings of the National Academy of Science, the animals typically conceive one to two days before giving birth.
Like all marsupials, swamp wallabies (Wallabia bicolor) give birth to tiny, immature babies that crawl to a special pouch where they nurse on their mother's milk. Some marsupials, like kangaroos, can mate and conceive about a day after birth, but not before, says Brandon Menzies, a study co-author and researcher with the University of Melbourne.
These wallabies are the only animal, besides the European brown hare, that can become pregnant while already pregnant. But the hares have distinct breeding seasons and are not continuously pregnant most or all of their adult lives, as female swamp wallabies are.
The study is important because "understanding the biology and endocrinology of reproduction in any species may have valuable lessons for human reproduction too," says David Gardner, at the same university, who wasn't involved in the paper.
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