Kleptoparasitism or cleptoparasitism (literally, parasitism by theft) is a form of feeding in which one animal takes prey or other food from another that has caught, collected, or otherwise prepared the food, including stored food (as in the case of cuckoo bees, which lay their eggs on the pollen masses made by other bees). The term is also used to describe the stealing of nest material or other inanimate objects from one animal by another.
The kleptoparasite gains prey or objects not otherwise obtainable or which otherwise require time and effort. However, the kleptoparasite might be injured by the victim in cases in which the latter defends its prey.
Kleptoparasitism may be intraspecific (the parasite is the same species as the victim) or interspecific (the parasite is a different species). In the latter case, the parasites are commonly close relatives of the organisms they parasitize ("Emery's Rule").
Animals that have extraordinarily specialized feeding methods are often targets of 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. A fox or a coyote could lose its kill to a brown bear, gray wolf, or even a bald eagle. 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. Chinstrap penguins also actively engage in kleptoparasitism, being known to steal rocks and other nest materials from members of their colony for use in their own nest.
There are many lineages of cuckoo bees, all of which lay their eggs in the nest cells of other bees within the same family. Bombus bohemicus, for example, parasitises several other species of Bombus, including Bombus terrestris, Bombus lucorum (white-tailed bumblebee), and Bombus cryptarum.
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The cuckoo wasps include the family Chrysididae. Many species of Chrisidid lay their eggs in the nests of potter and mud dauber wasps; other wasps parasitise related species, as for example Polistes sulcifer, which parasitises Polistes dominula. These insects are sometimes referred to as kleptoparasites; other terms used (not exact synonyms) are inquiline and brood parasite.
Some flies are kleptoparasites, which is especially common in the subfamily Miltogramminae of the family Sarcophagidae. There are also some kleptoparasites in the families Chloropidae and Milichiidae. Some adult milichiids, for example, visit spider webs where they scavenge on half-eaten stink bugs. Others are associated with robber flies (Asilidae), or Crematogaster ants. Flies in the genus Bengalia (Calliphoridae) steal food and pupae transported by ants and are often found beside their foraging trails. Musca albina (Muscidae) reportedly shows kleptoparasitic behaviour, laying eggs only in dung balls being interred by one out of several co-occurring dung-rolling scarab species.
Scarab dung beetles relocate vast amounts of vertebrate dung to establish their nests. A few species do not transport dung materials, but merely use reserves made by other species, either "roller" or "tunneller". Examples are the genus Cleptocaccobius (small species parasiting balls of roller dung beetles), and the genus Pedaria (whose species nidificate in the nests of large tunneller dung beetles in tropical Africa).
Many semiaquatic bugs (Heteroptera) are known to engage in kleptoparastism of prey. In one study, whenever the bug Velia caprai (water cricket) took prey heavier than 7.9 g, other bugs of the same species joined it and successfully ate parts of the prey.
Kleptoparasitic spiders, which steal or feed on prey captured by other spiders, are known to occur in five families:
Kleptoparasitism is relatively uncommon in birds. However, some non-passerine groups, such as skuas, jaegers and frigatebirds, rely extensively on such behavior to obtain food, and others—including raptors, gulls, terns, coots, and some ducks and shorebirds—will do so opportunistically. Among opportunistic species such as the roseate tern, research has found that parent birds involved in kleptoparasitism are more successful in raising broods than non-kleptoparasitic individuals. Bald eagles have also been seen attacking smaller raptors, such as ospreys, to steal fish away from them. Among passerine birds, there are fewer known examples of kleptoparasitism, though masked shrikes have been recorded stealing food from wheatears, and Eurasian blackbirds have been seen stealing smashed snails from other thrushes.
Skuas (including the smaller species known as jaegers in North America) are masters of piracy. Their victims are typically gulls and terns, though other fish-eating species (including auks) are also pursued until they disgorge their catches. The fact that skuas are swift and agile fliers—and that they sometimes gang up on a single victim—aid in their success rate.
During seabird nesting seasons, frigatebirds will soar above seabird colonies, waiting for parent birds to return to their nests with food for their young. As the returning birds approach the colony, the frigatebirds (which are fast and agile) drop down and pursue them vigorously; they have been known to seize tropicbirds by their long tail plumes. Many of the frigatebirds' colloquial names, including man-o'-war bird and pirate of the sea, are a clear reference to this kleptoparasitic behaviour. A study of kleptoparasitism in the magnificent frigatebird suggests that the amount of food obtained by kleptoparasitism may be marginal.
Gulls are the perpetrators as well as the victims of kleptoparasitism, with some species frequently exhibiting the behavior, particularly during the breeding season. While the victim is most often another member of the same species, other (principally smaller) gulls and terns are also targeted. In the Americas, Heermann's gulls, and laughing gulls are known to steal food from brown pelicans; as the pelicans surface and empty the water from their bills, the gulls lurk nearby and grab escaping food items. Several species of gull also steal food from humans, for example takeaway food at seaside resorts.
Several species of coots and gallinules have been recorded engaging in kleptoparasitism. American coots often feed in the company of other waterfowl species, and occasionally will rob diving ducks—including ring-necked ducks, redheads and canvasback—when they surface with food. Eurasian coots steal from conspecifics, as well as from diving and dabbling ducks, and swans. Allen's gallinules rob both conspecifics and African pygmy geese.
The relationship between spotted hyenas and lions, in which each species steals the other's kills, is a form of kleptoparasitism. Cheetahs are often targets of kleptoparasitism. Bears, coyotes and wolves are very opportunistic and all have this behavior. All hyena species engage in this behavior when they can, and jackals also steal from other carnivores' kills. Sperm whales sometimes steal fish from fishermen's lines, making them the largest of all kleptoparasites.
Three minutes later: this spotted hyena and another are running toward the kill
38 seconds later: The cheetah has fled without resistance. The vultures will also engage in kleptoparasitism: when the hyenas move a piece of the carcass, the vultures will take scraps from the ground.
Human intraspecific kleptoparasitism (humans taking food from other humans) is common in times of famine.
Humans take milk from mammals such as cows, goats, sheep, horses, and camels, and honey from bees.
One researcher saw humans chasing lions from captured prey in Waza National Park, Cameroon in 2006. Interviews with Bororo herdsmen suggest this behaviour, which possibly contributes to declining lion populations in the park, is more widespread than recognised.
Various crocodiles will steal food from other animals: the Nile crocodile is known to steal from big cats and hyenas.
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