Why do animals sometimes kill each other's offspring? Among hyenas, infanticide is a leading source of juvenile mortality; in all observed cases, killers were adult females, frequently higher-ranking than the mothers

Infanticide by females is a leading source of juvenile mortality in a large social carnivore. Ally Kelsey Brown et al. , Oct 17 2020. https://doi.org/10.1101/2020.05.02.074237

Rolf Degen's take: https://twitter.com/DegenRolf/status/1317687883348795392

Abstract: Social animals benefit from their group-mates, so why do they sometimes kill each other's offspring? A major barrier to understanding the evolution of infanticide is a lack of data from natural populations. Especially when perpetrated by females, infanticide remains poorly understood, because the increased mating opportunities that explain infanticide by males do not apply in females. Using 30 years of data from several spotted hyena groups, we show that infanticide is a leading source of juvenile mortality, and we describe the circumstances under which it occurs. In all observed cases, killers were adult females, but victims could be of both sexes. Killers only sometimes consumed the victims. Mothers sometimes cared for their deceased offspring, and sometimes consumed the body. Killers tended to be higher-ranking than the mothers of victims, and killers were sometimes aided by kin. Our results are consistent with theory that infanticide by females reflects competition among matrilines.

Key words: infanticide by females, matrilineal society, thanatology, female-female competition, nepotism