Hares, pikas and rabbits (Lagomorpha) are small terrestrial mammals that include cottontails, jackrabbits, pikas, hares and rabbits. The group is also commonly referred to as lagomorphs. There are about 80 species of lagomorphs divided into two subgroups, the pikas and the hares and rabbits.
Lagomorphs are not as diverse as many other mammal groups, but they are widespread. They inhabit every continent except Antarctica and are absent from only a few places around the globe such as parts of South America, Greenland, Indonesia and Madagascar. Although not native to Australia, lagomorphs have been introduced there by humans and have since successfully colonized many parts of the continent.
Lagomorphs generally have a short tail, large ears, wide-set eyes and narrow, slit-like nostrils that they can scrunch tightly closed. The two subgroups of lagomorphs differ considerably in their general appearance. Hares and rabbits are larger and have long hind legs, a short bushy tail and long ears. Pikas, on the other hand, in contrast, are smaller than hares and rabbits and more rotund. They have round bodies, short legs and a tiny, barely-visible tail. Their ears are prominent but are rounded and not as conspicuous as those of hares and rabbits.
Lagomorphs often form the foundation of many predator-prey relationships in the ecosystems they inhabit. As important prey animals, lagomorphs are hunted by animals such as carnivores, owls and birds of prey. Many of their physical characteristics and specializations have evolved as a means of helping them escape predation. For example, their large ears enable them to hear approaching danger better; the position of their eyes enables them to have a near 360-degree range of vision; their long legs enable them to run quickly and out-maneuver predators.
Lagomorphs are herbivores. They feed on grass, fruits, seeds, bark, roots, herbs and other plant material. Since the plants they eat are difficult to digest, they expel a wet fecal matter and eat it to ensure that the material passes through their digestive system twice. This enables them to extract as much nutrition as possible from their food.
Lagomorphs inhabit most terrestrial habitats including semi-deserts, grasslands, woodlands, tropical forests and arctic tundra. Their distribution is worldwide with the exception of Antarctica, southern South America, most islands, Australia, Madagascar, and the West Indies. Lagomorphs have been introduced by humans to many ranges in which they were not formerly found and often such introductions have lead to widespread colonization.
Lagomorphs are mammals. They are divided into two subgroups, the pikas and the hares and rabbits. The classification of lagomorphs is highly controversial. At one time, lagomorphs were considered to be rodents due to striking physical similarities between the two groups. But more recent molecular evidence has supported the notion that lagomorphs are no more related to rodents than they are to other mammal groups. For this reason they are now ranked as an entirely separate group of mammals.
The earliest representative of the lagomorphs is thought to be Hsiuannania, a ground dwelling herbivore that lived during the Paleocene in China. Hsiuannania is know from just a few fragments of teeth and jaw bones. Despite the scant fossil record for early lagomorphs, what evidence there is indicates that the lagomorph clade originated somewhere in Asia.
The earliest ancestor of rabbits and hares lived 55 million years ago in Mongolia. Pikas emerged about 50 million years ago during the Eocene. Pika evolution is difficult to resolve, as only seven species of pikas are represented in the fossil record.