Ahypercarnivore is ananimal that has a diet that is more than 70%meat, either via activepredation or byscavenging. The remaining non-meat diet may consist of non-animal foods such asfungi,fruits or other plant material.[1][2] Some extant examples of hypercarnivorous animals includecrocodilians,owls,shrikes,eagles,vultures,felids, some wildcanids,polar bear,odontocetid cetaceans (toothed whales),snakes,spiders,scorpions,mantises,marlins,groupers,piranhas and mostsharks. Every species in thefamilyFelidae, including the domesticatedcat, is a hypercarnivore in its natural state. Additionally, this term is also used inpaleobiology to describetaxa of animals which have an increased slicing component of theirdentition relative to the grinding component.[2] In domestic settings, e.g. cats may have a diet derived from only plant and synthetic sources using modern processing methods.[3] Feeding farmed animals such asalligators and crocodiles mostly or fully plant-based feed is sometimes done to save costs or as an environmentally friendly alternative.[4][5] Hypercarnivores are not necessarilyapex predators. For example,salmon are exclusively carnivorous, yet they are prey at all stages of life for a variety of organisms.
Many prehistoric mammals of thecladeCarnivoramorpha (Carnivora andMiacoidea withoutCreodonta), along with the early order Creodonta, and some mammals of the even earlier orderCimolesta, were hypercarnivores. The earliest carnivorous mammal is considered to beCimolestes, which existed during the LateCretaceous and earlyPaleogene periods in North America about 66 million years ago. Manytheropoddinosaurs such asTyrannosaurus rex that existed during the late Cretaceous, although not mammals, wereobligate carnivores.
Large hypercarnivores evolved frequently in thefossil record, often in response to an ecological opportunity afforded by the decline or extinction of previously dominant hypercarnivorous taxa. While the evolution of large size and carnivory may be favored at the individual level, it can lead to a macroevolutionary decline, wherein such extreme dietary specialization results in reduced population densities and a greater vulnerability for extinction.[6] As a result of these opposing forces, the fossil record ofcarnivores is dominated by successiveclades of hypercarnivores that diversify and decline, only to be replaced by new hypercarnivorous clades.
As an example of related species with differing diets, even though they diverged only 150,000 years ago,[7] thepolar bear is the most highly carnivorous bear (more than 90% of its diet is meat) while thegrizzly bear is one of the least carnivorous in many locales, with less than 10% of its diet being meat.[8][9][10]
The genomes of theTasmanian devil,killer whale, polar bear,leopard, lion,tiger,cheetah and domestic cat were analysed: shared positive selection for two genes have been found related to bone development and repair (DMP1,PTN), which is not a development seen in either omnivores or herbivores. This indicates that a stronger bone structure is a crucial requirement and drives selection towards predatory hypercarnivore lifestyle in mammals.[11][12] Positive selection of one gene related to enhanced bone mineralisation has been found in theScimitar-toothed cat (Homotherium latidens).[13]
Animals that live almost exclusively on food of animal origin are incapable of biosynthesizingarachidonic acid. This characteristic has been found in the lion, the domestic cat, theturbot, and even the haematophagousmosquito.[14]
In hypercarnivore mammals, the enzymealanine:glyoxylate aminotransferase is expressed mainly or exclusively in themitochondria, which would allowglyoxylate to be metabolised from thehydroxyproline present in animal matter.[15]
