There are several different causes of lion mortality, which include human predation, starvation and diseases, such as canine distemper virus. Infanticide often contributes to a high rate of mortality among lion cubs.
Lions often die violently, either as a consequence of poaching or because of fights with other lions. Humans often hunt lions because they view the cats as a threat. Lions fight with each other over territorial disputes or fight within the same pride over a kill. In addition, it is possible for a lion to be maimed while hunting and die because of the subsequent wounds.
Lions are also vulnerable to parasites and diseases. An outbreak of sable fly among a certain population of lions caused the lions to become emaciated and to have sores all over their bodies. As a result, the population dropped from 70 to only 15 as lions died or emigrated. In addition, lions are vulnerable to viruses, such as the feline immunodeficiency virus, the canine distemper virus and feline infective peritonitus.
Many lions die is as cubs. When male lions take over a pride, they want to be able to mate with females as soon as possible. As a result, they often kill off all cubs they find, contributing to high cub mortality.