Lagomorpha

Lagomorpha is a monophyletic order that diverged from other placental mammals during the Paleocene, with the earliest fossils dating to the Eocene of Asia and North America. The order is traditionally placed within the clade Glires, alongside rodents, based on molecular and morphological data. The two extant families, Leporidae and Ochotonidae, split around 37 million years ago, and the family Prolagidae, containing the Sardinian pika, went extinct in historical times. Fossil lagomorphs include giant forms such as Nuralagus rex from Menorca, which weighed up to 12 kg, and the North American Megalagus. Classification within the order has been refined by molecular phylogenetics, revealing that hares (genus Lepus) are more closely related to certain rabbits than to each other, and that the volcano rabbit (Romerolagus diazi) is a basal lineage within Leporidae.

Lagomorphs share a distinctive dental formula (2/1, 0/0, 3/2, 3/3) with a second pair of small peg-like incisors behind the large front pair, a trait that separates them from rodents. Their incisors grow continuously and are worn down by gnawing on fibrous vegetation. Lagomorphs are hindgut fermenters, digesting plant cellulose in an enlarged cecum and colon, and they practice coprophagy—reingesting soft fecal pellets to extract additional nutrients. Their digestive efficiency is lower than that of ruminants, but their rapid passage rate allows them to process large quantities of low-quality forage. The order also exhibits a unique mode of locomotion: rabbits and hares are saltatorial, using a galloping gait, while pikas are more cursorial. Their ears are large and vascularized, aiding in thermoregulation, and their eyes are positioned laterally for a wide field of view.

Lagomorphs occupy a wide range of habitats, from arctic tundra to tropical forests, and play crucial roles as prey and ecosystem engineers. Rabbits and hares are typically solitary or live in loose groups, while pikas are territorial and often form colonies in rocky talus or burrows. Many species exhibit crepuscular activity patterns, avoiding peak predator activity. Lagomorphs are a key food source for a diverse array of predators, including raptors, canids, and mustelids, and their grazing can shape plant community composition. Some species, such as the European rabbit (Oryctolagus cuniculus), are invasive in regions where they have been introduced, causing significant ecological and economic damage. Conversely, the critically endangered Amami rabbit (Pentalagus furnessi) is a relict species confined to two Japanese islands, highlighting the vulnerability of island lagomorphs.

Beyond the familiar rabbits and hares, Lagomorpha includes several obscure and surprising members. The hispid hare (Caprolagus hispidus), once thought extinct, survives in small populations in the Himalayan foothills. The Sumatran striped rabbit (Nesolagus netscheri) was rediscovered in 1998 after being unseen for decades, and its close relative, the Annamite striped rabbit, was described as new to science in 2000. Pikas, often overlooked, are notable for their vocalizations and haypile behavior, storing vegetation for winter. The extinct Sardinian pika (Prolagus sardus) was hunted by early humans and may have survived until the 18th century. Lagomorphs also have a unique reproductive strategy: female rabbits can conceive a second litter while still pregnant with the first, a phenomenon known as superfetation. Additionally, the order's name derives from the Greek lagos (hare) and morphe (form), reflecting their historical classification as rodents.

Coprophagy

The ingestion of feces, practiced by lagomorphs to re-digest food and absorb more nutrients.

Hindgut fermentation

A digestive process in which plant material is fermented in the cecum and colon, rather than in a multi-chambered stomach.

Leporidae

The family of rabbits and hares, characterized by long ears and powerful hind legs.

Ochotonidae

The family of pikas, small lagomorphs with short ears and no visible tail.

Superfetation

The occurrence of a second conception during an ongoing pregnancy, observed in some lagomorphs.