What is the term for male lions killing cubs sired by other males?

The term for male lions killing cubs sired by other males is infanticide. In lions, it most often occurs after a new coalition of males takes control of a pride and displaces the previous males.

The incoming males may kill existing cubs because lionesses that are nursing are usually unavailable to conceive again. Once their cubs die, the lionesses can return to oestrus sooner, allowing the new males to father offspring during their limited period of control. This is an example of sexually selected infanticide, in which eliminating unrelated young can increase the killer’s future reproductive success.

Lionesses do not simply accept this outcome. They may defend cubs aggressively, and cooperation among several females can improve their chances. Females may also mate with multiple males, which can make paternity uncertain and sometimes reduce the risk that a male will attack a cub. The behavior is not the same as “culling” or general population control: infanticide is the zoological term for intentional killing of young by an adult of the same species, whether or not the motive is reproductive competition.