Infanticide by females is a leading source of juvenile mortality in a large social carnivore

Social animals benefit from their group-mates, so why do they sometimes
kill each other’s offspring? Using 30 years of data from multiple groups
of wild spotted hyenas, we address three critical aims for understanding
infanticide in any species: (1) quantify the contribution of infanticide
to overall mortality (2) describe the circumstances under which
infanticide occurs and (3) evaluate hypotheses about the evolution of
infanticide. We find that, although observed only rarely, infanticide is
in fact a leading source of juvenile mortality. Infanticide accounted for
24% of juvenile mortality, and 1 in 10 hyenas born in our population
perished due to infanticide. In all observed cases of infanticide, killers
were adult females, but victims could be of both sexes. Of four hypotheses
regarding the evolution of infanticide, we found the most support for the
hypothesis that infanticide in spotted hyenas reflects competition over
social status among matrilines.