Surplus killing is the behavior predators exhibit when they kill more prey than they can immediately use. They may partially consume, cache, or abandon intact prey. This behavior has been observed in zooplankton, damselfly naiads, predaceous mites, weasels, honey badgers, wolves, orcas, red foxes, spotted hyenas, spiders, brown bear, lynx, mink, house cats, and humans. The term was invented by Dutch biologist Hans Kruuk after studying spotted hyenas in Africa[1] and red foxes in England.[2]
It is likely that this is a survival mechanism, the selection for aggressiveness toward prey being an evolutionary development toward becoming a more successful hunter.
Most cases of surplus killing occur when the prey is disadvantaged in some fashion. Under those conditions, the predator's energy expenditure and risk are low.