Cant and his team discovered that banded mongooses have a very peculiar reproductive system, in which the females will give birth to a communal litter, usually on the same day.

When females do give birth on different days, the pups born earliest almost always die within the first few days. Turns out, the other females will slaughter the first-born pups.

The researchers hypothesized that the females synchronize their births to escape from this threat of infanticide. “Only when the females can be certain that the litter does not contain any of her pups will they kill the litter,” Cant explained.

So, being enterprising scientists, they used hormone injections on selected females. In the first attempt, only the dominant females were allowed to successfully breed – not surprisingly, all of their litters survived. On the second attempt the researchers attempted the opposite with the subordinate females…with, shall we say, uglier results. Meaning, slaughter.

Researchers Hodge SJ, Bell MB and Michael Cant on PubMed via io9.