The researchers used selective breeding and high-resolution ultrasonography to demonstrate that a male hare can fertilize a female during late pregnancy. The resulting embryos will develop around four days before delivery of the first pregnancy. The embryos don’t have any place to go at that time, however, since the uterus is occupied by the embryos’ older brothers and sisters. So the embryos hang out in the oviduct, rather like when you wait in your car for a parking space to open up. Once the uterus is free, the embryos move in.
The result is that a female hare can shorten the time between litters from 42 to 38 days and deliver up to 35.4 percent more offspring during a breeding season.
Link | Photo by Flickr user Biillyboy used under Creative Commons license