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Rabbit Production. James I McNitt
Читать онлайн.Название Rabbit Production
Год выпуска 0
isbn 9781789244434
Автор произведения James I McNitt
Жанр Биология
Издательство Ingram
All breeds of domestic rabbits are descendants of the European wild rabbit, Oryctolagus cuniculus . Rabbits were originally classified as rodents but are now placed in a separate order, Lagomorpha, primarily because they have two more incisor teeth than rodents (six instead of four). The lagomorphs are divided into two major families: (1) pikas and (2) rabbits and hares.
Pikas, or rock rabbits, are common inhabitants of mountainous areas in North America and Asia (Fig. 1.2). In contrast to other lagomorphs, they are highly vocal, having a loud call or whistle. Pikas inhabit rocky areas of talus or piles of broken rock. They collect grass and other vegetation, which they cut and then allow to cure into hay in the sun. The hay is stored in piles in the rock crevices, to be used for winter feed. Pikas differ from rabbits in a number of fairly obvious characteristics, besides their whistling and calling. Both sexes lack the typical external sex organs of other animals and instead have a cloaca into which the fecal, urinary, and reproductive tract discharges are made.
Fig. 1.2. A pika or rock rabbit. Pikas, along with rabbits and hares, are members of the order Lagomorpha. (Courtesy of Justin Johnsen, licensed under the Creative Commons Attribution-Share Alike 3.0 unported license)
They have much less developed hind legs than rabbits and hares and resemble rodents in their appearance. Pikas are commonly seen or heard in high mountain areas, where they are often observed perched on rocks. A shrill whistle is used as an alarm signal. Unlike rabbits and hares, which are nocturnal, pikas, are most active by day.
Hares differ from rabbits in that they are born fully haired, with their eyes open, and can run within a few minutes of birth (Fig. 1.3). They are born in the open without a well-defined nest. They have long legs and take long leaps or bounds when running. Hares have long ears and are wary and alert. They can detect enemies at considerable distances and depend on their speed and endurance for escape. Hares are in the genus Lepus (e.g., Lepus europaeus -European hare; Lepus californicus -black-tailed jack rabbit). Some of the more common hares in North America are the jack rabbits of the western United States and Canada and of northern Mexico. Jack rabbits can become serious agricultural pests, causing great damage to crops and rangeland. In the past, rabbit drives were used to control them, whereas pesticide baits are now employed. The Arctic hare is found in northern Canada and in Alaska, Greenland, and Asia. The snow-shoe hare is found in most of Canada and the northern continental United States. Both the Arctic and snowshoe hares have different coat colors in summer and winter, being brown in summer and white in winter. The populations of snowshoe hares in northern areas fluctuate on about a 10- year cycle. Populations of their predators, such as the snowy owl and Canada lynx, fluctuate in a similar manner. The European hare is an important species for hunting in Europe. During the breeding season, European hares engage in courtship rituals involving dashing about wildly and leaping into the air, thus accounting for the expression “mad as a March hare.” High blood levels of the male hormone testosterone occur during the period of “March madness.”
Fig. 1.3. A jack rabbit. Jack rabbits are actually hares, close relatives of rabbits. (Courtesy of B.J. Verts)
The two main genera of rabbits are the true rabbits (Oryctolagus) and the cottontail rabbits (Sylvilagus) . Oryctolagus encompasses the wild European rabbit and its domesticated descendants, which include all the breeds of domestic rabbits. Sylvilagus includes a number of North American cottontails, such as the Eastern, Desert, Brush, Marsh, and Swamp cottontail rabbits.
Cottontails and domestic rabbits cannot be crossed. Laboratory investigations have shown that sperm and eggs of the two genera will fertilize, but the developing embryos die in a few hours, after about four cell divisions. The same is true for crosses of hares and rabbits. The lack of viability of the hybrid embryos is because of differences in chromosome numbers among the genera. There are 22 chromosome pairs in Oryctolagus, 21 in Sylvilagus, and 24 in Lepus.
The story of the domestication of rabbits is shrouded in mystery. It is believed that the original site of domestication was the Iberian Peninsula (Spain and Portugal and the south of France). The first recorded rabbit husbandry