Kleptoparasitism

Kleptoparasitism (literally, parasitism by theft) is a form of feeding where one animal takes prey from another that has caught, killed, or otherwise prepared it. The kleptoparasite gains either by obtaining prey that it could not obtain itself, or by saving the time and effort required to obtain the prey. However the kleptoparasite may run the risk of injury from the victim if it is able to defend its prey.

Kleptoparasitism may be intraspecific, where the parasite is the same species as the victim, or interspecific, where the parasite is a different species.

Animals that have unusual feeding methods often suffer kleptoparasitism. For example, oystercatchers are unusual in being able to break through the shells of mussels; adult oystercatchers suffer intraspecific kleptoparasitism from juveniles that are not yet strong or skillful enough to open mussels easily. Diving birds that bring their prey to the surface suffer interspecific kleptoparasitism from gulls, which are unable to fetch fish from the sea floor themselves.