Chapter 14 Mammals

The rabbit (Oryctolagus cunniculus)

Rabbits belong to the mammalian order Lagomorpha. They were originally classified with species such as rats, mice and hamsters as members of the order Rodentia because they all have chisel-shaped incisors that are open-rooted and continue to grow throughout the animal’s life. However, rabbits have two pairs of upper incisors while rodents have only one pair, leading to the reclassification of rabbits (and the related hares and pikas) as lagomorphs. Rabbits are burrowing herbivorous animals that live in large social groups. They are readily preyed upon by carnivores and much of their anatomy is adapted to sensing danger and making a rapid escape.

Tables 14.1 and 14.2 give physiological and reproductive parameters for rabbits.


The wild European rabbit, Oryctolagus cuniculus, from which all our modern breeds are derived, weighs about 2.5 kg and is covered in brown ticked fur, often described as agouti-coloured. This colouration creates a dappled effect, which breaks up the outline and helps camouflage the individual. Selective breeding has led to the development of about 50 breeds of domestic rabbit ranging in weight from 1–8 kg, with a variety of fur textures and colours, many of which would be unsuitable for life in the wild.

The head is rounded, with long, black-tipped upright ear pinnae set high on either side. They are large, representing approximately 12% of the body surface, and very vascular, which enables them to be used as a means of thermoregulation. The pinnae are extremely mobile and are designed to pick up sounds of danger. The lop breeds of rabbit have been developed to have ears that hang downwards.

The eyes are protuberant and set on either side of the head, providing a wide range of monocular vision to detect predators. Rabbits are crepuscular, i.e. active at dawn and dusk, and their sight is adapted to lower light intensities. The lips are soft and covered in sensitive hairs. The upper lip is divided by a deep philtrum, which enables the rabbit to nibble grass very short.

Mature female rabbits develop a large fold of skin under the chin known as the dewlap from which they pull fur to line their nests before giving birth. The skin of the rabbit is well supplied with scent glands, which are used for territorial marking. They can be found under the chin, at the anus and on either side of the perineum.

The forelegs are relatively short and used for digging, while the hind legs are longer and provide the propulsive force for the characteristic hopping method of locomotion. They also kick the earth away when the rabbit is digging its burrow. There are five toes on each forepaw and four on each hind foot. Each toe ends in a sharp claw, those of the hind feet being long and straight. The feet are entirely covered in fur and there are no footpads.

When the rabbit is at rest, the entire plantar surface of the hind limb from toes to hock rests on the ground. When grazing, among a group of rabbits there will always be one or two standing upright on their hind legs, watching for predators. If danger threatens they will thump their hind legs on the ground to warn the others. Both of these behavioural patterns can be seen in pet rabbits. Rabbits have short fluffy tails with white undersides. As the rabbit runs the white colouration ‘flashes’ to warn the rest of the group of possible danger.

Digestive system

Rabbits are herbivorous and have been likened to ‘little horses’ in that both the rabbit and the horse are hindgut fermenters, i.e. the main chamber for the breakdown of plant material is part of the large intestine. Unlike the horse, however, the digestive system of the rabbit allows for rapid passage of food through the tract and rapid elimination of fibre. This has enabled the body size and weight of the rabbit to remain small, which allows the animal to show the speed and agility necessary to escape predators. By contrast, in the horse, fibre remains in the gut for some time, necessitating the evolution of a large-volumed fermentation chamber and consequently a large body size (see Ch. 16). The digestive tract of the rabbit (Fig. 14.3) is relatively long and makes up 10–20% of body weight.

Reproductive system

Jul 18, 2016 | Posted by in PHARMACOLOGY, TOXICOLOGY & THERAPEUTICS | Comments Off on Mammals

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