Kleptoparasitism (originally speltclepto-parasitism,[1][2] meaning "parasitism bytheft") is a form offeeding in which one animal deliberately takes food from another. The strategy isevolutionarily stable when stealing is less costly than direct feeding, such as when food is scarce or when victims are abundant. Many kleptoparasites arearthropods, especially bees and wasps, but including some true flies, dung beetles, bugs, and spiders.Cuckoo bees are specialized kleptoparasites which lay their eggs either on the pollen masses made by other bees, or on the insect hosts ofparasitoid wasps. They are an instance ofEmery's rule, which states that insect social parasites tend to be closely related to their hosts. The behavior occurs, too, in vertebrates including birds such asskuas, which persistently chase other seabirds until they disgorge their food, and carnivorous mammals such asspotted hyenas andlions. Other species opportunistically indulge in kleptoparasitism.
Kleptoparasitism is a feeding strategy where one animal deliberately steals food from another. This may be intraspecific, involving stealing from members of the same species, or interspecific, from members of other species.[3][4] The term denotes a form ofparasitism involvingtheft, from Greek κλέπτω (kléptō, 'steal').[5] The strategy has been widely studied inbirds; in four families, allseabirds, theFregatidae,Chionididae,Stercoraridae, andLaridae, it occurs in more than a quarter of the species.[6][4]
Such a strategy should be followed only if it isevolutionarily stable, meaning that it offers aselective advantage to individuals that practise it. Kleptoparasitism costs time and energy which could otherwise be spent directly on feeding, so this cost must be outweighed by the benefit in energy gained from the stolen food. Mathematical modelling suggests that when food is abundant, ordinary feeding is the best strategy; when food abundance falls below a critical level, kleptoparasitism suddenly becomes advantageous, and aggressive interactions become common. Similarly, when potential victims are rare or widely dispersed, the time needed to find them may not be justified by the food that might be stolen from them, resulting infrequency-dependent selection.[3][6]
There are many lineages ofcuckoo bees, all of which lay their eggs in the nest cells of otherbees, often within the same family.[7]Bombus bohemicus, for example, parasitises several other species in its genus, includingB. terrestris,B. lucorum, andB. cryptarum.[8] These are instances ofEmery's rule, named for the Italian entomologistCarlo Emery, which asserts thatsocial parasites among insects, including kleptoparasites, tend to be closely related to their hosts.[9][10] The largestmonophyletic lineage of kleptoparasitic bees isNomadinae (a subfamily ofApidae), which comprises several hundred species in 35 genera.[11]
| Host genus | Parasite genus |
|---|---|
| Bombus | Bombus (Psithyrus) |
| Anthophora | Melecta,Zacosmia |
| Amegilla | Thyreus |
| Megachile | Coelioxys |
Thecuckoo wasps (Chrysididae) lay their eggs in the nests ofpotter andmud dauber wasps. Other families ofwasps have "cuckoo" species that parasitise related species, as for examplePolistes sulcifer, which parasitises a related species,P. dominula.[12][13] Numerous other wasp families have genera or larger lineages of which some or all members are kleptoparasitic (e.g., the genusCeropales inPompilidae and the tribeNyssonini inCrabronidae).[7] Some of these species areinquilines andbrood parasites rather than kleptoparasites.[14]
Others are dubbed kleptoparasitoids, namelyparasitoids that select hosts that have been parasitized by another female. Kleptoparasitoids may make use of the punctures made by previous parasitoids on their hosts; may follow the trails or traces left by parasitoids to locate hosts; or use hosts already weakened by other parasitoids.[15] Especially the latter is referred to as pirate parasitism.[16]
Sometrue flies (Diptera) are kleptoparasites; the strategy is especially common in the subfamilyMiltogramminae of the familySarcophagidae. There are also some kleptoparasites in thefamiliesChloropidae andMilichiidae. Some adult milichiids, for example, visitspider webs where they scavenge on half-eatenstink bugs. Others are associated with robber flies (Asilidae), orCrematogasterants.[17] Flies in the genusBengalia (Calliphoridae) steal food and pupae transported byants and are often found beside their foraging trails.[18]Musca albina (Muscidae) reportedly shows kleptoparasitic behaviour, laying eggs only in dung balls being interred by one of several co-occurring dung-rollingscarab species.[19]
Scarabdung beetles relocate large amounts of vertebrate dung, rolling balls of the material to their nests for their larvae to feed on. Several smaller species of dung beetle do not gather dung themselves but take it from the nests of larger species. For example, species ofOnthophagus enter dung-balls whileScarabeus beetles are making them.[20]
Many semiaquatic bugs (Heteroptera) are kleptoparasitic on their own species. In one study, whenever the bugVelia 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.[21]
Kleptoparasiticspiders, which steal or feed on prey captured by other spiders, are known to occur in five families:
A few bird species are specialist kleptoparasites, while many others are opportunistic.Skuas (including jaegers) andfrigatebirds rely heavily on chasing other seabirds to obtain food. Other species—includingraptors,gulls,terns,coots, and someducks andshorebirds—do so opportunistically. Among opportunists such as theroseate tern, parent birds involved in kleptoparasitism are more successful in raising broods than non-kleptoparasitic individuals.[23][24]Bald eagles have been seen attacking smaller raptors, such asospreys, to steal fish from them.[25] Amongpasserine birds,masked shrikes have been recorded stealing food fromwheatears,[26] andEurasian blackbirds have been recorded stealing smashedsnails from otherthrushes.[23]
Duringseabird nesting seasons, frigatebirds soar aboveseabird colonies, waiting for parent birds to return to theirnests with food for their young. As the returning birds approach the colony, the frigatebirds, which are fast and agile, swoop in to pursue them vigorously; they sometimes seizetropicbirds by their long tail plumes. The namefrigatebird, as well as many of the frigatebirds' colloquial names, includingman-o'-war bird andpirate of the sea, denote this behaviour.[27] However, the amount of food obtained by kleptoparasitism in themagnificent frigatebird may be marginal.[28]
Gulls are both perpetrators and victims of opportunistic kleptoparasitism, particularly during the breeding season. While the victim is most often another member of the same species, other (principally smaller) gulls and terns can also be targeted. In theAmericas, asbrown pelicans surface and empty the water from their bills, they sometimes have their food stolen byHeermann's gulls andlaughing gulls, which lurk nearby and grab escaping food items.[29]Great black-backed gulls are skilled kleptoparasites, stealing from other gulls and from raptors. Several species of gull steal food from humans, for example takeaway food at seaside resorts.[30]
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The relationship betweenspotted hyenas andlions, in which each species steals the other's kills,[31] is a form of kleptoparasitism.[21] Cheetahs are common targets. Bears, coyotes and wolves are very opportunistic and all have this behavior.Crab-eating macaques have also exhibited kleptoparasitic behaviors. Allhyena species engage in this behavior when they can, as dojackals.[32] Human hunters may commonly take the remains of fresh kills from other carnivores, such as lions andEurasian lynx.[33][34][35]Risso's dolphins have been observed charging "head-on" atsperm whales, causing them to open their mouths; it has been suggested that the observed harassment results in someregurgitation, and that the food is then eaten by the Risso's dolphins. The behaviour is rare and may be opportunistic.[36]
