Rabbits – Small Animals, Big Adaptations

Rabbits are mammals often used as pets by us. They look cute and the little children love playing with them. Rabbits belong to the class Mammalia and order Lagomorpha with family Leporidae. They are cosmopolitan in distribution. Seven genera within the family Leporidae are generally classified as rabbits. Rabbits are basically herbivorous animals and prefer to live in meadow, woods, forest, thickets and grasslands. They also inhabit deserts and wetlands. They prefer to live in groups by making underground burrows. A group of burrows is called as warren.

Majority of rabbit population has been reported from North America. They are natives of Europe, Southeast Asia, Sumatra, some islands of Japan, and in parts of Africa and South America. They are absent in Euresia where major population of hares dwell. Rabbits have first entered the South America during the Great America Interchange but the southern cone of South America lacks any species of rabbit. The Tapeti species of rabbit dominates South America. Presently European rabbits have been introduced in many parts of the world.

Rabbits bear long ears about 10 cm in length which are an adaptation for the detection of the predators. Hind legs are powerful for running fast. Front two paws have 5 toes and the extra one is called as dewclaw. Hind feet have 4 toes. Rabbits are digitigrades running with the tips of the toes. Wild rabbits may reach a length of 20 -50 cm weighing about 0.4-2 kg. Fur is generally long, soft with shades of brown, gray and buff and the tail includes a little plume of brownish fur. The epiglottis is present just over the palate so rabbit is an obligate nasal breather. Two sets of incisors are present just behind each other. They share a common lineage with rodents and are now often referred to as members of superclass Glires.

The major proportion of digestion occurs in the large intestine and the caecum so they are hindgut digesters. Caecum is about 10 times longer than the stomach and the large intestine makes about 40% of the digestive tract of rabbits. The special and unique musculature of the caecum facilitates the separation of more digestible matter from the fibrous material so that effective digestion may commence and the fibrous material may leave the body as feces. Rabbits are known to eat their faeces showing the phenomenon of coprophagy. Cecotropes are sometimes called as the night feaces and are consumed by rabbits as they are made of more nutritious elements like vitamins, minerals and proteins wrapped in the mucous lining of caecum. They are essential for rabbit’s health.

Rabbits are the prey of carnivores so they tend to remind confined in the underground burrows. They have a good sense of vision. Teeth are strong and serve for eating as well as biting the foe in order to escape from its grip. Reproductive rate is higher in these animals. Breeding season is from February to October. In Australia and New Zealand breeding occurs during the months of late July to January. Gestation period is of about 30 days. The normal litter contains 4-12 babies but the size of litter is large in larger species. A single female rabbit can produce about 800 children, grandchildren and great-grand children in one season. A doe is ready to breed at the age of 6 months and the buck at the age of 7 months. Courtship and mating occurs only for a short duration lasting in about 30-40 seconds. Courtship behaviour involves licking, sniffing and following the doe. Urine is also sprayed over the doe as a part of sexual behaviour. Females are reflex ovulators. Lumps of hairs are also lost by the female rabbit during sexual behaviour.

Ovulation commences in about 10 hours after mating. After mating female makes nest with the fur of the dewlap, flanks and belly regions. Removal of fur exposes the nipples of female so that it can nurse her babies well. The babies are altricial which means when they are born they are blind, naked and helpless. Babies attain passive immunity prior to birth through the placental transfer. The eyes of the babies open after 10-11 days after birth and they start eating on their own at the age of 14 days. The babies develop a soft body coat after few days of their birth whih is replaced by a pre-adult coat at the age of 5-6 weeks. This pre-adult coat is further replaced by the adult coat at the age of 6-8 months. The final adult coat is shed twice in a year. Rabbit milk is highly nutritious so the babies need the milk only twice a day. The overall life span of a rabbit is around 9-12 years and the longest lived species had an average life span of 18 years.

Rabbits are herbivores and prefer to feed on grass, leaf stuffs and forbs. The diet is chiefly composed of cellulose which is hard to digest. This problem has been solved by them by passing out two types of faeces one in the form of hard droppings and other in the form of soft, black and viscous pellets. The soft ones are immediately consumed by them as they pass out as they are rich source of nutrients. The grazing period varies considerably. The fist half an hour of grazing consists of rapid grazing followed by half an hour of selective grazing. During selective grazing rabbits pass out hard dropping which are not reingested. If the environment appears to be free from the enemies they continue to graze for prolonged intervals. Reingestion of the soft pellets has been observed early in the morning at around 8 o’clock and 5 o’clock in the evening inside the burrows.

The hard droppings are made up of plant cuticle and stalk being formed after the reingestion of the soft pellets. They are released outside the burrow and are not eaten back. Soft pellets are produced after the hard droppings have been excreted out generally after grazing. Soft pellets chiefly composed of micro-organisms and undigested plant cell walls. Chewed plant material gets collects in the secondary chamber called as the caecum present between small and large intestine housing large proportion of symbiotic bacteria that produes vitamin as well as cellulose enzyme to carry out the digestion of cellulose. Soft pellets contain about 56% of bacteria by dry weight and 24.4% proteins are also present in them. Pellets remain intact in the stomach for about 6 hours after reingestion and the bacteria present continue to digest the plant carbohydrates in them. This process of reingestion helps the rabbit to get maximum benefit of nutrients which have been lost during the first passage of feces. This process serves the same function as found in the ruminating cattle and sheep. They are incapable of vomiting due to the physiology of their digestive system.

Rabbits can be easily distinguished from the hares as the young one of rabbit are born naked, blind (altricial) while those of hairs are with hair and are able to see (precocial). All rabbits except the cotton tails live in burrows while hares live in simple nests just above the ground. Hares are larger than rabbits with long ears and with black markings on their fur. They are wild and cannot be domesticated like the European rabbits. Rabbits have been kept as pets since time immemorial. Pet rabbits are often called as house rabbits are kept in cages placed inside the rooms. They can often be trained for particular tasks. Some pet rabbits are kept in hutches during the day but are brought back inside the rooms in the night. Wild hares are consumed as food in Europe, South America, North America and many parts of Middle East. They are also sold by the butchers in markets in UK and Australia. When used for food rabbits are both hunted and bred for meat. Guns are used for capturing them. Cuniculture is a practice of rearing of rabbits for meat and this practice is popular in some parts of the globe. Fur of rabbits is often used for making scarves and hats. Angora rabbits are bred for their long, fine hairs. The faecal matter is a good source of manure for the plants and the rabbit milk is a rich source of protein.

Rabbits are also a source of menace to humans as their reproductive rate is very high and they cause considerable damage to the agricultural crops. They hold a considerable important place in cultural and religious beliefs. They are symbols of fertility and rebirth and have been designated as the Easter Bunny. They are also the symbols of playful sexuality which relates to human perception of innocence as well as its reputation as a prolific breeder.

Nature has gifted a specific role to every individual to perform. Rabbits apart from being used a source of entertainment, meat and fur deserves a special place in ecosystem.