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, wolves, orcas, red foxes, spotted hyenas, spiders, brown bear, lynx, and mink.

The term was invented by Dutch biologist Hans Kruuk after studying spotted hyenas in Africa and red foxes in England.

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.

References

• Jennifer L. Maupin and Susan Reichert, Superfluous killing in spiders.
• Joseph K. Gaydos, Stephen Raverty,Robin W. Baird, and Richard W. Osborne, SUSPECTED SURPLUS KILLING OF HARBOR SEAL PUPS (PHOCA VITULINA) BY KILLER WHALES (ORCINUS ORCA).
• William G. George and Timothy Kimmel, A Slaughter of Mice by Common Crows.
• Wolf Trust, Wolf Depredation-Surplus Killing'.
• Wildlife Online: Foxes-Surplus Killing, Why do foxes kill to excess....
• For Wolves: Ralph Maughan Wolf Report, Jackson Trio makes some surplus kills.
• High Country News, Zachary Smith, Wolf pack wiped out for ‘surplus killing’.
• Victor Van Ballenberghe, Technical Information on Wolf Ecology and Wolf/Prey Relationships.
• Ned Rozell, Far North Grizzlies Develop Taste for Muskoxen.
• Pierre-Yves Daoust, Andrew Boyne, Ted D’Eon, Surplus killing of Roseate Terns and Common Terns by a mink.
• RayDerPhan, Killer whales hunting young seals (video).