Female kangaroos have two vaginas and two uteruses. They also have a third canal that is used solely for birth.

Female kangaroos have what are called paired lateral vaginae. These are for the purpose of transporting the sperm to the womb, but there is a midline pseudovaginal canal for actually giving birth.

Male kangaroos have a two-pronged penis to accommodate the females two vaginas.

This is an adaptation that enhances the survival prospects of the kangaroo in Australia's harsh climate. The kangaroo has something called embryonic diapause: the mother kangaroo spends most of her adult life pregnant, but in drought times, she has the ability to indefinitely "freeze" the development of the young embryo until food sources are replenished. Having two vaginas enables the embryo, when ready, to pass to the birth canal, or the median vagina while another embryo waits in suspended development.

Incidentally, having two vaginas, 2 fallopian tubes, 2 uteruses and 2 cervixes is a feature of almost all marsupials. Scientists have theorised that this might be why the young joeys are born so small, but this has not, of course, been proven.