Killing of Cape fur seal (Arctocephalus pusillus pusillus) pups by brown hyenas (Parahyaena brunnea) at mainland breeding colonies along the coastal Namib Desert

Abstract

Brown hyenas (Parahyaena brunnea) scavenge and kill seal pups at mainland Cape fur seal (Arctocephalus pusillus pusillus) colonies. The prey encounter interval and interval between kills depended on seal density, and increased density resulted in an increase of the capture rate and increase in hunting efficiency from 14% in November to 47% in January. The time brown hyenas spent at the seal colony decreased with increasing seal density and increasing air temperatures. Nevertheless, they were regularly active during the day when less adult seals were present at the colony, which indicates that the attendance of adult seals might play a role in the choice of foraging time. Brown hyenas killed seal pups throughout the study period. The predation rate was independent of the availability of non-violent mortalities, but the absolute number of kills was positively density-dependent. Mass kill events were recorded throughout the study period and are therefore not unusual occurrences. The overabundance of easy and vulnerable prey may lead to an over stimulus situation that triggers killing independent of the consumption of the prey or the hunger state.