The technical term for mammals in theorderCarnivora iscarnivoran, and they are so-named because most member species in the group have a carnivorous diet, but the similarity of the name of the order and the name of the diet causes confusion.
Many but not all carnivorans are meat eaters; a few, such as thelarge and small cats (Felidae) areobligate carnivores (see below). Other classes of carnivore are highly variable. Theursids (bears), for example: while the Arcticpolar bear eats meat almost exclusively (more than 90% of its diet is meat), almost all other bear species areomnivorous, and one species, thegiant panda, is nearly exclusivelyherbivorous.[3]
Dietary carnivory is not a distinguishing trait of theorder. Many mammals with highly carnivorous diets arenot members of the order Carnivora.Cetaceans, for example, all eat other animals, but are paradoxically members of the almost exclusivelyplant-eatinghooved mammals.
Animals that depend solely on animal flesh for their nutrient requirements in nature are calledhypercarnivores orobligate carnivores, whilst those that also consume non-animal food are calledmesocarnivores, orfacultative carnivores, oromnivores (there are no clear distinctions).[2] A carnivore at the top of thefood chain (adults not preyed upon by other animals) is termed anapex predator, regardless of whether it is anobligate orfacultative carnivore. In captivity or domestic settings, obligate carnivores like cats and crocodiles can, in principle, get all their required nutrients from processed food made from plant and synthetic sources.[4][5]
Carnivores may alternatively be classified according to the percentage of meat in their diet. The diet of ahypercarnivore consists of more than 70% meat, that of amesocarnivore 30–70%, and that of ahypocarnivore less than 30%, with the balance consisting of non-animal foods, such asfruits, other plant material, orfungi.
Omnivores also consume both animal and non-animal food, and apart from their more general definition, there is no clearly defined ratio of plant vs. animal material that distinguishes afacultative carnivore from anomnivore.[6]
TheBengal tiger's largecanines and strong jaws reveal its place as anapex predator.Lions are voracious carnivores; they require more than 7 kilograms of meat daily. A major component of their diet is the meat of largemammals, such as thisbuffalo.
Obligate or "true" carnivores are those whose diet requires nutrients found only in animal flesh in the wild. While obligate carnivores might be able toingest small amounts of plant matter, they lack the necessaryphysiology required to fullydigest it. Some obligate carnivorous mammals will ingest vegetation as anemetic, a food that upsets their stomachs, to self-induce vomiting.[7]
Obligate carnivores are diverse. The amphibianaxolotl consumes mainly worms and larvae in its environment, but if necessary will consume algae. All wildfelids, including feraldomestic cats, require a diet of primarily animal flesh and organs.[8] Specifically, cats have high protein requirements and their metabolisms appear unable to synthesize essential nutrients such asretinol,arginine,taurine, andarachidonic acid; thus, in nature, they must consume flesh to supply these nutrients.[9]
Characteristics commonly associated with carnivores include strength, speed, and keen senses for hunting, as well as teeth and claws for capturing and tearing prey. However, some carnivores do not hunt and arescavengers, lacking the physical characteristics to bring down prey; in addition, most hunting carnivores will scavenge when the opportunity arises. Carnivores have comparatively short digestive systems, as they are not required to break down the tough cellulose found in plants.
Many hunting animals have evolved eyes facing forward, enabling depth perception. This is almost universal among mammalian predators, while most reptile and amphibian predators have eyes facing sideways.
The earliest predators weremicroorganisms, which engulfed and "swallowed" other smallercells (i.e.phagocytosis) anddigested them internally. Because the earliest fossil record is poor, these first predators could date back anywhere between 1 and over 2.7 bya (billion years ago).[10]
The rise ofeukaryotic cells at around 2.7 bya, the rise of multicellular organisms at about 2 bya, and the rise ofmotile predators (around 600 Mya – 2 bya, probably around 1 bya) have all been attributed to early predatory behavior, and many very early remains show evidence of boreholes or other markings attributed to small predator species.[10]
The dominance of temnospondyls around the wetland habitats throughout theCarboniferous forced other amphibians to evolve intoamniotes that had adaptations that allowed them to live farther away from water bodies. These amniotes began to evolve both carnivory, which was a natural transition from insectivory requiring minimal adaptation; andherbivory, which took advantage of the abundance ofcoal forestfoliage but in contrast required a complex set of adaptations that was necessary for digesting on thecellulose- andlignin-rich plant materials.[12] After theCarboniferous rainforest collapse, bothsynapsid andsauropsid amniotes quickly gained dominance as the top terrestrial animals during the subsequentPermian period. Some scientists assert thatsphenacodontoid synapsids such asDimetrodon "were the first terrestrial vertebrate to develop the curved, serrated teeth that enable a predator to eat prey much larger than itself".[13]
Though the theropods were the larger carnivores, several carnivorous mammal groups were already present. Most notable are thegobiconodontids, thetriconodontidJugulator, thedeltatheroidans andCimolestes. Many of these, such asRepenomamus,Jugulator andCimolestes, were among the largest mammals in their faunal assemblages, capable of attacking dinosaurs.[14][15][16]
Most carnivorous mammals, fromdogs todeltatheridiums, share several dental adaptations, such ascarnassial teeth, longcanines and even similar tooth replacement patterns.[17] Most aberrant arethylacoleonids, with a diprodontan dentition completely unlike that of any other mammal; andeutriconodonts like gobiconodontids andJugulator, with a three-cusp anatomy which nevertheless functioned similarly to carnassials.[14][18]
^Ullrey, Duane E. "Omnivores".Encyclopedia of Animal Science. Mammals.
^Armstrong, P. Jane; Gross, Kathy L.; Becvarova, Iveta; Debraekeleer, Jacques (2010)."Introduction to Feeding Normal Cats"(PDF).Small Animal Clinical Nutrition. pp. 371–372.Archived(PDF) from the original on 12 May 2021. Retrieved17 January 2022.Because grass is not digested within the cat's gastrointestinal (GI) tract, it acts as a local irritant and sometimes stimulates vomiting. Thus, grass eating may serve as a purgative to eliminate hair or other indigestible material.
^abKielan-Jaworowska, Zofia; Cifelli, Richard L.; Luo, Zhe-Xi (2004). "Chapter 12: Metatherians".Mammals from the Age of Dinosaurs: Origins, evolution, and structure. New York, NY: Columbia University Press. pp. 425–262.ISBN0-231-11918-6.
^Fox, Richard C. (2015). "A revision of the late Cretaceous–Paleocene eutherian mammalCimolestes(Marsh, 1889)".Canadian Journal of Earth Sciences.52 (12):1137–1149.Bibcode:2015CaJES..52.1137F.doi:10.1139/cjes-2015-0113.
