ACS Distance Education UK
Terrestrial carnivores range in length from the least weasel 5-10” 26 g (1 oz) to the polar bear at 3.1 m 10 feet length , and in mass 1000kg (2,200 lb). Males carnivores are commonly larger than females. Aquatic carnivores have a smaller size range but greater maximum size, due to their aquatic habitat demanding greater thermoregulation through larger body size with layers of protecting fat and being able to supporting high body mass. The smallest seals are about 5 feet in length and 150lb in weight, with the largest the southern elephant seal (Mirounga leonine) weighing up to 5,000kg (11,000lb) and 6.9m (23 feet) in length. The size of carnivores that predate individually on other individual animals is adapted to their prey size, but not so much with pack hunting carnivores. Most tend to be medium size animals -if too small they wouldn’t be big enough to overpower and kill prey.
Carnivores are anatomically adapted to their various habitats to provide for locomotion, feeding, and thermoregulation and for sexual competition. Adaptations for locomotion provide for migration and predation and so depend on the carnivore’s habitat, ranging from aquatic, through terrestrial to arboreal. These include elongated legs for grassy plains in the maned wolf (Chrysocyon brachyurus), for hunting on high grassy plains, or with cheetahs for speed. All terrestrial predators are covered with shiny hair and fur of colours ranging from black to white, and in many shades of red/brown that may also include manes. Many animals have evolved to blend into their habitats, becoming camouflage, and with carnivores this assists in their hunting skills and allows them to ambush prey. A perfect example o this is the Tiger (Panthera tigris). The stripes on these large felines have assisted in their hunting skills and allows them to blend in with their environment. The Sumatran Tiger (Panthera tigris sumatrae) has adapted to have dark rustic fur with black stripes, and this assists them in blending into their jungle habitat. On the other hand the Siberian Tiger (Panthera tigris altaica) has adapted to having narrower stripes across the rustic fur, with more white patches, and this allows them to blend into their habitat of broadleaf and coniferous forests, and mountain ranges. Giant pandas (Ailuropoda melanoleuca) which diverged from other bears 23 million years ago, have evolved a 6th thumb from their wrist bone for grasping bamboo, and their molars are smoother and larger than those of other bears to crush bamboo but their canine teeth remain large for defence. Unlike Black Bears (Ursus americanis), Brown Bears (Ursus arctos) have adapted long, sharp claws which assist in digging dens and moving soil.
After the Cretaceous-Tertiary mass extinction, including the dinosaurs, there was a rapid diversification of ancestral mammals during the early Palaeocene period (65-55 million years ago) that included the rapid evolution and diversification of the Carnivores finally resulting in a wide range of terrestrial and aquatic species. Terrestrial carnivores have four legs, however, in seals the legs have become adapted to flippers from locomotion. All carnivores have claws made of keratin that may be non-retractable (dogs), semi non-retractable (cheetahs) or retractable (cats); retraction actually refers to withdrawal into a sheath not into a pocket.
This diversification included feeding habits driven by carnivore size and potential prey. Of terrestrial carnivores some completely carnivorous (tigers, polar bears, cheetahs, dog packs), others are omnivorous (foxes, skunks, badgers, bears), filter feeder of krill (some seals), or even herbivorous (giant pandas). All aquatic carnivores live entirely on animal prey including krill (monk seals, Lobodon carcinophaga), shellfish and benthic organisms (walrus, Odobenus rosmarus), and the shark ratfish, flatfish, crab, squid, octopus (southern elephant seal). Carnovores that only eat meat are termed obligate carnivores or hypercarnivores, species include many cats. Mesocarnovores such as racoons, coyotes and foxes normally have a diet consisting of about 50% meat and are omnivorous in their dietary habits. Carnivores that have diet that include less than 30% meat are termed hypocarnivores, an example is a the giant panda. Adaption’s to their skulls and teeth reflect carnivores diets. Some species such as the filter feeding crabeater seal have specialised krill-filtering cusp teeth, and walrus have greatly extended canines in the form of tusks.
Carnivores have large oral cavities and a large mouth size to assist in grabbing prey. Face muscles are reduces to enable a large gape size, and the jaws have a simple hinge in plane with the teeth. The temporalis muscle is massive and accounts for most of the bulk of the sides of the head.
The teeth of carnivores are spaced so as to not trap stringy debris. Canines are greatly elongated for stabbing, tearing, and killing prey. A common distinguishing characteristic of carnivores is that most have characteristic enlarged teeth (ie. fourth upper premolar; and first lower molar); which work together to effectively cut and shear off pieces of meat and tendon. Together these teeth are called the “carnassial pair”. Some carnivores (eg. bears, racoons and seals) have secondary modifications to the “carnassial pair” making them different to the typical carnivore animal. All carnivores also have incisors (teeth in the front centre) for grasping and tearing with the third incisor, next to the canines, frequently enlarged and more conical shaped. Predators do not mix digestive enzymes in their mouths but swallow large pieces whole. They have simple digestive systems and stomachs that have a high acidity capable of easily digesting bone. Carnivores can consume large amount of meat with one meal, for instance tigers can consume up to 80lb (45kg) of meat at one time from a deer kill, and consume about 50 deer sized prey a year. Meat tends to digest quicker than plant matter, and with this the intestines of carnivores is much shorter. Nutrient absorption occurs in the intestine so with a diet which consist of meat, there is no need to have long intestine.