Pikas, Rabbits and Hares are related species, all belonging to the order 'Lagomorphs'. When considering differences between them, the most useful considerations are size, behavior, distribution and habitat, as they share many traits.
Pikas are the smallest of the three animals, reaching a length of about 8 inches (20cm). There are 15 species in all, most of which live in mountainous areas of Asia. However, two species are known in north America, the Rock Pika and the Burrowing Pika. Both are specially adapted for life in a cold environment, inhabiting areas such as the Rockies and high grassland, and cannot endure warm temperatures. Their call is a whistle, emitted at times of excitement. The Rock Pika has more in common with Hares and the Burrowing Pika more in common with Rabbits as regards social behavior and breeding. Rock Pikas are solitary animals or form pairs. They produce 2-3 young per year after a gestation of about a month. Burrowing Pikas live in larger groups and can produce 20 young in a year, though the mortality rate is high.
Rabbits, Oryctolagus cuniculus, are much larger than Pikas, growing to 12 to 16 inches in length (30-40cm) and weighing 1 1/2 to 2 kilograms, (3.3 to 4.4 lbs) They originated around the Mediterranean Sea and have been introduced into Britain, Australia, New Zealand, Chile and America. They have successfully adapted to a wide variety of habitats, heathland, arable farmland, open grassland, deciduous woods and sand dunes. They avoid high altitude and coniferous woodlands. Unlike Hares, they live communally in warrens, a series of connected burrows 1-2 meters long, and they can breed all the year round. The young are born after a gestation of 28-30 days and are blind, deaf, naked and helpless. A typical litter numbers 3-12 kits, which wean at 28 days and are sexually mature at 4 months!
There are several different species of Hares. Hares can be found from the high Arctic through Europe and Asia into Africa. Species such as the European Brown Hare, Lepus capensis(europaeus), are larger than Rabbits, which they superficially resemble when seen at a distance. Brown Hares grow to 20 to 24 inches in length (52-60cm) and weigh from 3.2 to 3.9 kilograms, (7lbs to 8lbs 10 ozs). Hares tend to be solitary animals except at breeding time in late winter and early spring, when they can be seen in small courtship groups. Males investigating unresponsive females are fended off with the forepaws in a display often likened to boxing. Young are born after a 42-44 day gestation. The typical litter is three leverets, which are born eyes open and covered in hair. They can run within 1 day of birth and are weaned at 1 week old. Soon after this they become independent, but are not sexually mature until 8 months old.
Brown Hares do not burrow and make warrens, they live in 'forms', shallow scrapes in the soil above ground amid sheltering vegetation. They rely on lying motionless in the daytime to avoid detection by predators, but if startled avoid capture by accelerating away on their long, powerful legs. They are faster runners than Rabbits or Pikas and rely entirely on speed to escape foxes and other predators.
Hares are deeply rooted in British, Irish and European folklore, which spread around the globe with colonization. Hares were sacred animals to the Celts of Britain and Ireland. In the writings of Taliesin, Gwion was said to have sought to escape Ceridwen's vengeance by shape-shifting into a hare. Later, in post-Roman England, they were seen as the sacred beast of Eostre, the Anglo-Saxon Goddess of fertility whose cult was celebrated at Easter. The 'Easter Bunny' probably has its origins here. Easter eggs may derive from the mistaken belief that Hares laid eggs; Lapwings, (Vanellus vanellus) lay their eggs in spring in open land such as Brown Hares frequent. There seems to be no such associations with Pikas or Rabbits!