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Bun Biology 101

Rabbits belong to a family known as leporids (along with hares).  They are no longer classified as a rodent.  The domestic rabbit (Oryctolagus cuniculus) originated from the European wild rabbit. There are many other species of rabbit, and these, along with cottontails, pikas and hares make up the Order Lagomorpha.  The full taxonomy is:

Order: Lagamorpha
Family: Leporidae (rabbits and hares)
Genus: Lepus, hares
Genus: Cylvilagus, cottontail rabbit
Genus & Species: Oryctolagus cuniculus, European or true rabbit

Rabbits are gregarious animals that live in burrows in open fields and along hedgerows. They are nocturnal, coming out of the burrows in the evening and retiring in the early morning. Grasses and other herbaceous plants are foods of choice; the bark of woody plants are eaten if herbaceous plants are not available. (Lousiana Vet. Med. Assoc.)

Anatomy and Physiology (from LVMA)

Adult body weight: NZW: 2 - 6 kg (female); 2 - 5 kg (male)
Life span: 5 - 6 years
Respiratory rate: 32 - 60 breaths/minute
Heart rate: 130 - 325 beats/minute
Normal average rectal temperature: 102.5F
  • The dental formula is 2(I 2/1, C 0/0, P 3/2, M 3/3) = 28. All teeth are open rooted and grow continuously.
  • The cecum is large, thin-walled, coiled, and terminates in the thick-walled light-colored vermiform process or cecal-appendix. This appendix contains a large amount of lymphoid tissue. Just proximal to the cecum is another gastrointestinal structure containing a large amount of lymphoid tissue, the sacculus rotundus.
  • The left lung consists of two lobes, the right lung consists of four lobes.
  • The right atrioventricular valve of the heart, called the tricuspid valve in human, has two cusps.
  • The rabbit possesses a well-developed nictitating membrane, the third eyelid.
  • The uterus is duplex with separate cervical and uterine openings.
  • There are usually four pairs of mammary glands.
  • The bones are relatively lightweight and represent only 8% of the body weight of the rabbit, compared to 13% in the cat. The rabbit has strong musculature.
  • The highly vascularized ears are important in thermoregulation.
  • Rabbit neutrophils contain eosinophilic granules and are termed heterophils. These heterophils may be confused with eosinophils and are distinguished by their cellular size and granule size (smaller than eosinophils), and the intensity of the granule staining (less intense than eosinophils). The larger granules of eosinophils often obscure the nucleus.
  • The normal urine pH is 8.2. The urine of young rabbits is free of precipitate but albuminuria is normal; the urine of mature rabbits is cloudy due to the presence of ammonium magnesium phosphate and calcium carbonate crystals. The color may vary from tan to reddish-orange, the latter color being due to the presence of porphyrin and bilirubin derivatives. This reddish-orange color is intensified during dehydration or by certain pigmented or high calcium diets, and must be differentiated from hematuria (blood in the urine).

Picture at upper left is courtesy of Sluggy Freelance



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