Marsupials are unusual mammals, found mostly in Australia and New Guinea. They give birth to live young called joeys which are incompletely developed, the joeys then move to their mother’s pouch where they nurse until fully developed. While these facts are strange enough, researchers have just discovered that the swamp wallaby’s reproductive strategy is even more unusual — they can be continuously pregnant.
A team of researchers from the Leibniz Institute for Zoo and Wildlife Research and the University of Melbourne have been able to demonstrate that a female swamp wallaby can conceive a new pregnancy while already pregnant. This means that a female already carrying a fetus ovulates while pregnant can mate with a male creating a new embryo. This newly formed embryo is then essentially put on pause until the mother gives birth to her joey and raises it. Once this first joey leaves the pouch nine months later the paused pregnancy is un-paused, and the cycle begins again.
The swamp wallaby manages this unusual feat by having two separated uteri and cervices. They are also able to produce two different kinds of milk for their young at two different development stages. This unusual adaptation that blurs the normal stages of reproduction must provide the swamp wallaby with an evolutionary advantage, although further study of the species will be required to learn more.
Source: Phys Org
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