Rodents are the world's most widespread, adaptable, and prolific group of mammals. They reproduce well, grow fast, learn quickly, and adapt to a wide variety of local conditions. Many convert vegetation into meat efficiently, digesting some fiber, even though their stomach, like man's, is a simple one.
It seems probable, therefore, that some species would make suitable microlivestock - a notion supported by the previous domestication of the guinea pig, laboratory rat and mouse, gerbil, and hamster. Indeed, "ranching" rodents might be an effective way to increase food supplies in remote areas. It could also be a mechanism to ensure the survival of rare rodents whose natural habitats are being rapidly destroyed.
RODENTS AS FOOD
Rodents are already common foods in many countries and are valued items of commerce. It has been estimated that 42 of 383 cultures eat rodents.! But the fact that they are a major meat source is almost unrecognized. This is due in part to cultural misunderstanding. Rodents suitable for human food or other products do not live in filth, like common rats. They are clean and vegetarian. Like rabbits, they eat grass and grains.
In some regions of the world, cooked rodent meat is regarded as the epitome of dining. In many countries, local rodent species are the most eagerly sought meats. City markets in different parts of Latin America carry guinea pig, pace, capybara, and vizcacha. Markets in Asia may carry rice rats, cloud rats, and bandicoot rats. Those of rural Africa are filled with "bushmeats" - usually including grasscutters, giant rats, and several other rodent species. These are often preferred to the meat of domestic stock and fetch higher prices than beef. And the amounts of rodent bushmeat available are not minor. In one year, for example, hunters in Botswana have brought to market 3.3 million kg of meat of the rodent called springhare (see page 278).
Fondness for rodent meat is not restricted to the tropics. In the United States, squirrel was once a much sought treat. Fat, nut-fed grey squirrels went into Brunswick stew, which has been called the most famous dish to emerge from the campfires and cabins of Colonial America. Thomas Jefferson liked it. Today, squirrel is the country's number two game animal (after deer), and many are still eaten.
Ancient Romans kept fat dormice in captivity, serving them as a delicacy. "The fat dormice are fattened up in barrel-like pots like those in country houses," wrote Varro (116-27 BC). "One feeds these animals large amounts of acorns, chestnuts, or other nuts."2 This small rodent remains a prized food in Europe and still appears on tables in certain areas. The meat is regarded as a delicacy because it tastes of almonds and other nuts. Often it is roasted, broiled, and cooked with its cracklings.
Rodents have seldom been included in livestock programs or economic development plans. Yet human appetite has actually caused the extinction of a number of species. Caribbean Indians ate several endemic rodents (one of which was as big as a bear), and may have caused several species to become extinct just before the time of Columbus. Others may soon follow the same dismal route, including the beautiful cloud rat of the Philippines, the hare-like mare of Argentina, the vizcacha of southern South America, and the gentle hutias of the Caribbean.
The guinea pig is described in a later chapter, but as it is the epitome of a rodent microlivestock species, some historical background is given here. It was domesticated for food use at least 7,000 years ago, probably in what is now the central highlands of Peru and Bolivia. With only llama and deer available, the prehistoric Andean peoples had few readily available sources of meat. They adopted wild cavies, and found that these rangeland rodents (which are more closely related to porcupines than to rats or mice) were gentle, manageable, and easy to rear. By the time the Spaniards arrived in the 1500s, the "cuy" (pronounced "coo-ee," like the faint cry it makes) was a major food from Argentina to the Caribbean.
This impressed the conquistadores, who introduced cuys into Europe, where they also became a delicacy.3 Within a century, these easily transported animals began to appear on tables in many parts of the Spanish empire. Guinea pigs are now reared in campesino huts in the mountains of central Mexico, in the Philippines, and in several African nations, along with other areas of the world.
Elsewhere, guinea pigs came to be used only as house pets and laboratory animals. Although during World War II Mussolini's government urged Italians to keep them to supplement their meager meat rations, their use as food was largely ignored in most parts of the world.
The idea of domesticating rodents may seem radical, but domestication projects are already under way with capybara in Venezuela (see page 206), pace in Panama (see next page and page 262), giant rat in Nigeria (see page 224), and the grasscutter in Ghana (see page 232). Rodent husbandry is not complicated and the animals' environmental requirements seem relatively simple and easy to satisfy. Moreover, rodents are not usually fastidious feeders, and being essentially vegetarian will readily accept a wide variety of commonly available foodstuffs.
As with most animals with which man is in close contact, rodents can transmit human diseases.4 With care, however, managed rodents need not be any more dangerous to care for or to eat than pigs or horses - both of which are worldwide food resources.
To domesticate the pace (see page 262) would seem to be impossible. These large rodents of Central and South America are nocturnal and fiercely territorial; they have low fecundity and take 10 months to reach weaning, and they have tender skin that is easily damaged Most researchers have written them off as candidates for domestication. But at least two have undertaken to beat the odds. We present the findings of one of them here to show that, using modem techniques, even species that normally fight each other to the death on sight are potential farm animals.
Through years of studying paces in Panama, Smithsonian biologist Nicholas Smythe has found that with care and planning the aggressive behavior can be so radically altered that the animals become calm. Indeed, some become almost loving. Newborns, Smythe found, undergo "imprinting" and when he places them with docile adults or with humans, the fierce territoriality never develops. He nurses newborns on "surrogate" mothers that have been imprinted on people. The youngsters then welcome human company and, if fumed out of the cage, return there voluntarily. "It's difficult to imagine a more manageable animal," Smythe said. "Technically speaking they are behaviorally indistinguishable from traditional domestic animals."
As of this writing, Smythe has three generations totalling about 50 individuals, and has several "families" of gentle paces living together in harmony. He has observed that they lose their nocturnal habit and, although they live mainly on fruits in the wild, they readily eat leafy vegetables and other foods in captivity. His captive specimens have recently begun to breed. The offspring remain docile, but they have so far averaged only a little more than two young per female per year.
"If we can just double the reproduction rate, then raising paces can compete economically with raising cattle," Smythe explained. "The potential for a bigger brood is all in the animal's anatomy, and if successful, paces in the wet tropics could produce as much protein as cattle."*
Pacas need the shade and protection of the forest. Thus, pace raising might provide an alternative to cutting down rainforests for cattle raising. Instead of toppling trees and planting pastures, people could farm paces in the forest, and perhaps make as much or more money at the same time. In tropical America, the ready acceptance of pace meat is a near guarantee that all they produce will be snapped up at premium prices. In the past, many territorial and aggressive species have been dismissed as being impossible to domesticate or manage. But Smythe has demonstrated that with imprinting and other methods of behavior modification, these need be dismissed no longer.
Indeed, the pace may already be becoming a new domesticated species. In the first stage of his experiments, Smythe had to train his captive-born paces to be social and nonaggressive. Subsequent generations, however, need no training adopt the new behavior patterns of the parents, and do not revert to aggressive asocial behavior. By the third generation, they have become as accepting of, and indifferent to, people as cattle or sheep.
15 Agouti[edit | edit source]
Among the best known of all animals of the American tropics, agoutis (Dasyprocta species)' are prolific rabbit- or hare-sized rodents that are probably easily farmed. They are valued for food and are hunted throughout most of their range. Indeed, agouti meat, once common in Latin markets. is now difficult to find because of indiscriminate killing. Agouti hunting is already prohibited in Brazil; restaurants in Belem, for example, once offered a variety of "cotta" (agouti) dishes at prices equivalent to those of choice filet mignon, but since the early 1970s they have been banned from serving it. Other countries will probably have to institute similar bans.
Agoutis are active, long-legged, and high-strung. They flee in panic at the slightest alarm. They do not climb but they do burrow occasionally, being essentially specialized ground-dwellers that live in tropical forest regions.
There have been no organized scientific attempts to raise these swift, shy animals in captivity, but Latin Americans sometimes keep them as "domestics," especially in parks and large gardens. (Agoutis are well known, for instance at the Goeldi Museum in Belem, Brazil.) These animals seem to tame easily, and could perhaps be mass produced on a large scale like rabbits or guinea pigs. They make affectionate pets, sometimes refusing to return to the wild. A research project on captive breeding of two local agouti species (Dasyprocta mexicana and D. punctata) for food is already under way in Tuxtla Gutierrez, Mexico.
AREA OF POTENTIAL USE
Most of lowland, tropical Latin America and the Caribbean.
APPEARANCE AND SIZE
Agoutis are delicately built, graceful, nimble, and beautifully proportioned. They have slender bodies, short ears, and look somewhat like a rabbit that has been "jacked up" in back. Generally, adults are 40-60 cm long and weigh 2-5 kg. Some are even bigger.
They run well and are good jumpers. From a standing start an agouti reportedly can leap as high as 2 m or as far as 6 m; however, as long as they are well fed, there is little problem keeping them behind a wall only 1 m high.2 Reportedly, they sometimes climb easy-sloping trees to collect green fruits, but researchers studying Central American agoutis report that they are strictly terrestrial.3 They swim well.
The body hair is thick, coarse, and glossy: pale orange to black on the back, and white to yellow on the belly. Some species have faint stripes, and some have a rump that contrasts with the rest of the back. The short tail is partially concealed under the long body hair.
Agoutis occur over a vast area from southern Mexico to Paraguay, including many islands in the Caribbean.4
Because they occasionally damage sugarcane plantings and because the meat is particularly tasty, people hunt agoutis relentlessly, especially near cities and towns. Now, in the l990s, they are becoming rare because of excessive hunting and habitat destruction. Many Latin Americans have never heard of them. In Mexico, for instance, there are few places where agoutis survive, and Dasyprocta mexicana may become extinct if habitat destruction and overhunting continue in its restricted range. In Costa Rica and Panama, agoutis occur only where there is little or no hunting or human interference.
HABITAT AND ENVIRONMENT
From sea level to elevations of at least 2,500 m, the adaptable agouti lives in many habitats: moist lowland forests, dry upland forests, thick brush, and savannas. However, although they thrive in secondary growth areas, they are mainly forest dwellers. Nonetheless, they often enter fields to forage, and young animals occasionally are seen in open areas such as grassy stream banks and cultivated fields.
Agoutis shelter in hollows among boulders, in riverbanks, or under tree roots. They also hide in heavy brush and sometimes in holes dug out by other species.
These herbivores eat seeds, fruit, stalks, leaves, roots, and other succulent plant parts, as well as occasional insects and fungi.
They seem to mate twice each year. The estrous cycle is variable, but is only about 34 days long. The young are born after a gestation period of 3.5-4 months. Usually, there are twins; however, single births and triplets have been recorded. Newborns are fully developed and are able to run around within hours. They start feeding on solids within a few days. Puberty occurs at about 9 months of age. Life expectancy is 10 years or more.
In the wild, agoutis are shy and retiring. Every sense seems constantly triggered for instantaneous action and sometimes they become hysterical. If danger threatens, they usually "freeze," but when discovered they stamp their feet as an alarm signal and dash away, nimbly dodging obstacles.
Despite excessive timidity, they can be violent among themselves.
In undisturbed forests, agoutis are diurnal and are often seen. But around villages they become nocturnal, as a means of self-preservation.
For the most part, these rodents live in loosely formed pairs, with previous litters living around their territory as "satellites." There is some "bigamy," some "philandering," and some "divorce."5.
Despite their long claws, they display much finger dexterity. To eat, they usually sit erect, crouching on their haunches and holding the food in their forepaws. If it has a skin' they carefully peel it before starting their meal. They save some nonperishable foods (nuts, for instance) by digging holes in scattered locations, dropping each one in a separate location, stamping it down, and covering it over. This behavior helps disperse the seeds of many species of trees so that agoutis benefit tropical forests and reforestation.
As noted, agoutis are popular game animals. They are often hunted with dogs that even follow them into the burrows. Agouti meat is tasty, although it is usually said to fall short of the meat of the pace (see page 262) because it is leaner and gamier.
Agoutis adapt well to captivity. With appropriate care they can be bred without difficulty.6 The nervousness that is pronounced in nature is quickly lost in captivity. The young become tame pets. They can be fed on foods such as leafy vegetables, fruit, potatoes, and bread scraps. Although many wild specimens have become nocturnal, captives readily readapt to daylight.
Being entirely terrestrial, agoutis require no trees, but they do need space. Given enough area, they get on well (with each other and with different species), and they breed freely. To avoid fighting, it seems necessary to separate females from males at puberty. Probably removing progeny from breeding pens at weaning could also help avoid most of the interpersonal aggression. In large areas with plenty of cover (banana plants, for instance), groups can be kept, but breeding may be disappointing. Husbandry may be most appropriate in large enclosures (50-100 agoutis) with some animals then removed to small cages 0.5-1 m° for selective feeding.
Close relatives, the green and red acouchies (Myoprocta acouchy and Myoprocta exilis) also deserve study. These are smaller animals with longer tails, bearing a little plume of white hairs. Although even more delicate and hypersensitive than agoutis, they can be kept in captivity and breed well. They then become less nervous and are easily handled. Acouchies. show remarkable intelligence and even some affection for those they trust. They frequent rainforests, but are rare or even absent in disturbed areas. Adults weigh up to 1.5 kg.
The general biology (diet, reproduction, activity rhythm), is almost the same as that of the agouti, but they live in smaller home ranges (0.6-1.2 hectares versus 2.5 hectares for the agouti) and travel singly, although belonging to a well-established family unit. Adult males tolerate the juvenile males. They occur only in Colombia, the Guianas, Ecuador, Peru, and Brazil.
Farming methods would probably be the same as for the agoutis, but acouchies always need plant cover.
Agoutis are appropriately sized: a dressed carcass can weigh 1-3 kg. The meat is good, and large commercial undertakings in urban centers could profit from the ready market that already exists.
The animals are prolific: females can produce up to two litters a year, each litter averaging two offspring. In protected areas, populations may grow fast.
These forest dwellers might provide a source of meat and income without destroying the forests in favor of cattle pastures. Also, they thrive in disturbed areas as long as there is some cover.
Experiments in Brazil show that agoutis are highly susceptible to foot-and-mouth disease.
The animals might become pests: they eat the roots, leaves, and fruit of agricultural crops and occasionally damage sugarcane and banana plants. However, current experience suggests that if they escape captivity they are quickly caught by hunters and do not reach pest levels.
Live agoutis have strong-smelling anal glands that may be offensive to breeders or could contaminate the meat if the animals are carelessly handled.
Where the rainforest is destroyed, the agouti population is destroyed. The animals were once well known throughout Latin America, but not anymore. In some areas, therefore, wild breeding stock may not be locally available. Moreover, people may have become sufficiently unfamiliar with them that their value may no longer be appreciated.
In captivity, they can be the prey of large birds such as eagles.
RESEARCH AND CONSERVATION NEEDS
The taxonomy of agouti species needs clarification.
Husbandry experiments are required, including studies on topics such as:
- Growth rate;
- Shelters and enclosures;
- Reproduction; and
- Techniques for catching, moving, marketing, and managing the animals.
One area where agoutis might profitably be raised is in enclosures in palm plantations. Palms such as the babassu provide food, shade, and shelter, while fallen and rotten logs offer secure retreats from predators. This deserves investigation.8
Instead of clearing vast areas of rainforest for cattle pasture, as is being done in much of Latin America, people might well "farm" agouties in the forests. Few of the settlers flooding into such regions can afford, let alone raise, beef. Small-scale agouti farming offers a promising and inexpensive alternative that would be gentle on the fragile land.
16 Capybara[edit | edit source]
The capybara (Hydrochoerus hydrochaeris), the world's largest rodent, can be as big as a sheep and weigh as much as a small person. Its natural habitat is the environs of South America's rivers, marshlands, and swamps, where it feeds on the grasses and reeds that grow near water.1
Because of its size, tasty meat, valuable leather, and rapid reproduction, the capybara is a candidate for both ranching and intensive husbandry throughout the hot and humid lowland tropical regions of Latin America. It seems easy to handle. It is commonly raised in zoos or occasionally as a pet, and has, in at least one instance, been proven successful in large commercial herds.
In floodplain ecosystems, capybaras complement cattle because they prefer to graze swamp grasses rather than the dryland grasses on which cattle feed. They have simple stomachs, but are one of the more efficient herbivores. Although they are "selective feeders" that eat lush waterside grasses "preserved in quality" by the water, they also graze pasture, usually selecting new growth that is often too short and scattered for cattle, with their large muzzles, to eat.
AREA OF POTENTIAL USE
The floodplains of the South American subtropics and tropics where the animal is indigenous.
APPEARANCE AND SIZE
Although they have blunt, horselike heads, capybaras look like gigantic guinea pigs. They are ponderous, barrel shaped, and have a tail too small to be seen from a distance. Their skin is tough and covered by sparse, bristlelike hairs: the color above is reddish brown to gray; beneath, it is yellowish brown.
The front legs are shorter than the back. Slightly webbed toes - four on the front feet and three on the back - make them good swimmers. They dive with ease and can stay underwater for up to five minutes. They also move nimbly on land.
The capybara is extremely large for a rodent. In size and color, it looks much like a pig. Often more than 100 cm long and 50 cm high at the shoulder, it can exceed 50 kg liveweight. Indeed, specimens weighing up to 90 kg have been reported.
Before livestock were introduced, the capybara grazed widely over riverine regions throughout South and Central America. Today, it is found in the flooded grasslands from Panama to Paraguay. Mainly, it occurs in the watersheds of the Orinoco, Amazon, Paraguay, and Parana rivers. High population densities exist in the Pantanal of western Brazil and on the Llanos floodplains of Venezuela and Colombia.
There are few precise population counts, but capybaras can occur in large numbers.2 However, in many areas they appear to be on the verge of extinction, being deliberately eradicated by farmers who think they compete with cattle and transmit diseases. Also, in some areas illegal hunting goes on year-round and great numbers are killed. The animals are particularly vulnerable during the dry season, when they concentrate around the diminished river channels and water holes.
HABITAT AND ENVIRONMENT
As noted, most capybaras live in swampy or grassy areas bordering rivers. However, some are found in other habitats, ranging from open plains to tropical rainforests. But even here they stay near ponds, lakes, streams, and swamps, and never venture much more than 500 m from water.
The capybara, like all rodents, is a simple-stomached animal, but it is a true herbivore. Its digestive system is especially adapted for fibrous materials. The large cecum - the site of enzymatic digestion- serves a function like that of the rumen of sheep, cattle, and goats. It has a digestive capacity similar to that of a sheep's rumen.
Like rabbits and all the rodents, capybaras are coprophagous. That is, during the morning hours when they are resting, soft feces from the cecum are passed a second time through the digestive system.3
Contributing to the animal's digestive ability is its efficient mastication. It chews its forage seemingly incessantly, reducing it to extremely small particles before it is swallowed.
Under natural conditions, the females annually bear 1 or 2 litters, each averaging from 4 to 6 offspring. Birth weight is between 1 and 2 kg, depending on litter size and sex. Both males and females reach sexual maturity when they reach a liveweight of 30 kg or more- usually between the first and second year of life.
Capybaras are intelligent, shy, inoffensive, and harmless. In undisturbed ecosystems, they are gregarious and live in family groups of up to 30. The young follow the mother about for many months after birth.
Unlike most rodents, they do not construct dens, but the groups have specific resting areas.
The animals are both diurnal and nocturnal and, like many herbivores, they graze at daybreak and dusk, and perhaps also at midnight. They spend the morning resting in weeds on riverbanks, and at noon they cool off by bathing for an hour or so before grazing. They may feed belly deep in water.
Capybaras wallow in mud, allowing it to dry on their skin before bathing again. Mange can develop in captivity when they cannot take a mud bath.
When startled, a capybara barks loudly and dashes away, but after running 200 m or so it tires, slows down, and may lapse into hyperthermia. At that point a hunter can easily catch it. However, if the animal reaches water, it usually eludes the pursuer because it swims so well - especially underwater.
Capybara meat is white and has qualities and properties (such as high emulsification) that might allow it to compete with pork and other meats in the food industry. Spanish-style sausages, Italian-style mortadellas, frankfurters, and German-style smoked chops have been produced experimentally.4 However, at present, the meat is mainly consumed only in the dried and salted form. It is particularly popular in Venezuela, where more than 400 tons are sold every year, especially during Easter festivities.5
The capybara's hide is one of the best for glove making. This luxury product, known in international commerce as carpincho leather, fetches high prices on European markets because it is more heat resistant than most leathers and because it stretches in only one direction. This one way grain allows gloves to stretch sideways without lengthening and looking sloppy.
The capybara appears suitable for raising as a livestock animal. Amerindians traditionally collected capybara orphans during the hunting season and raised them until needed for food. Capybara breeding was reported in Brazil as early as 1565.
Modern attempts have been made towards domestication. Researchers at the Institute of Animal Production in Venezuela, for instance, started a breeding program in the 1970s using 20 females and 5 males. Since that time they have continuously kept capybaras in confinement. Through selection and management, they have improved the reproduction of captive animals. The current aim is to get 16 offspring per mother per year. Newborns are weaned after 5 weeks and the mother is returned to the breeding pen.6 In Colombia, similar work is in progress, and guidelines for raising capybaras on breeding farms have been published.7 In Brazil, research has been carried out to study capybara nutrition, genetics, management, reproduction, and social behavior in total confinement.8
Throughout South America, the price of beef has increased greatly within the last few years, thereby providing a new incentive for capybara husbandry. It has also forced many campesinos to eat more wildlife, which adds another incentive for producing capybara meat on farms and thereby perhaps helping to relieve pressure on the wild stocks.
When tame, the animals are amenable to handling without physical restraint. They are so tractable that in Surinam a blind man once used one as a guide animal.
Capybaras can be raised on a variety of readily available vegetation: leaves, roots, fruits, and vegetables. They thrive in coarse grasses, if given opportunity to select nutritious parts. Their large incisors allow them to bite off short grasses that many herbivores cannot use. For instance, they eat "capybara grass" (Paspalum fasciculatum) that is abundant on river edges in Venezuela and is normally too short for cattle to graze. This makes for low-cost feeding and utilization of a resource that is otherwise unused.
Capybaras are at home in hot, humid environments and are fully adapted to life on the tropical floodplains and seasonally flooded savannas. They thrive in extreme climates where cattle struggle, such as in the parts of the lower Paraguayan Chaco where summer temperatures reach 45°C.9 An ecological benefit to raising capybaras is that there is no need to alter habitats by introducing exotic forage plants.
They reproduce quickly. Age at first conception for females is about 1.5 years, and the time between parturitions is generally shorter than that of goats or sheep in the tropics. Young capybaras grow so fast that in 18 months they can reach a liveweight of more than 40 kg. In their natural conditions, they are more disease resistant than cattle. The annual productivity is said to exceed that of cattle in many parts of its range.
This species is already so widely eaten in South America that the meat from farmed animals should be readily acceptable.
Capybaras occasionally raid fields and can harm sugarcane, rice, bananas, sweet potatoes, cassava, corn, and other crops. In many parts of Brazil, they are considered agricultural pests and are shot.
Confining these animals in high density may create serious problems. Infectious diseases and parasite outbreaks seem to be worse than those that occur with conventional livestock. Aggression might prove a limitation to capybara husbandry: it is almost impossible to cage two adult males together or to introduce new animals to an existing group.
The animals may transmit disease to people and livestock. They can harbor foot-and-mouth disease and are known to be susceptible to brucellosis. They also carry a form of trypanosome, Trypanosoma evansi.
Compared with cattle, capybara use only a small proportion of the total plant biomass. They are largely selective feeders, and for satisfactory performance must have sufficient area to select the plants they need. If placed in a paddock of only coarse grass, most will eventually die. Like goats and gazelles, capybara probably select a diet that is at least 15 percent richer in crude protein than a typical cattle diet.'°
High mortality has never been observed in Venezuela, but keeping the animals alive on a farm in some areas may not be easy. In one trial, more than half (55 percent) of the capybara died of disease, and a few of septicemia (the result of wounds incurred during fights), but most apparently of trypanosomiasis. Other losses were caused by speeding vehicles (29 percent), poaching (6 percent), and predation, mainly by jaguars (12 percent)."
RESEARCH AND CONSERVATION NEEDS
It is important for researchers to undertake the following:
- Gather specimens from different regions for comparative evaluation.
- Assess experiences of zoos and farms.
- Undertake nutritional trials.
- Initiate captive breeding trials - measurements of growth rates, space requirements, feed needs.
- Characterize the animal's productivity.
- Study the capybara's basic physiology and production potentials.
- Investigate biological factors, such as reproductive physiology, and social behavior (both in the wild and under controlled conditions).
- Determine the factors influencing capybara reproduction, growth, and development.
- Determine the animal's adaptability and economic merit in various farming systems.
- Study the influence of environment on reproduction rate.
- Determine their complementarily with water buffalo or other ruminants that normally use swampy habitats.
- Determine relative causes of mortality (such as diseases specific to capybaras) and predation (especially of the young) by spectacled caiman, crested caracayes, black vultures, and others.
17 Coypu[edit | edit source]
The coypu' (Myocastor coypus) is an aquatic rodent native to South America. It has been called the "South American beaver," but its size is actually closer to that of a small dog or an agouti. It seems suited to be a microlivestock species because, compared with most rodents' it has a large body size and a relatively high reproduction rate. Moreover, it is easy to manage, and there is much literature on how to raise it in captivity.2
Fur is the main item of commercial value. In the late 19th century, it was in such high demand that the animal was nearly exterminated. However, in 1922 Argentineans began raising coypu in captivity and this practice spread through South America and to other regions. In many European countries and in various locations in the United States some specimens escaped or were released, and coypu have become established in the waterways.
Coypu meat is tasty and is consumed in many regions of South America as well as in parts of Europe. Because of the absence of musk glands, the meat is free of the "gamy" flavor found in squirrels and rabbits. It is moist, fine "rained, medium light in color, and firm. It is one of the mildest and tenderest of wild meats.
AREA OF POTENTIAL USE
This animal has been widely distributed, but its area of safest use is within its natural range in South America.
APPEARANCE AND SIZE
The coypu is adapted to a semiaquatic existence and has webbed feet, valvular nostrils that can be closed to keep water out, and underfur that remains dry even under water. Its long, powerful claws on the forefeet are used for grooming, excavating burrows, and digging up and holding food. The tail is slender; the extremely large incisor teeth are orange-red.
An adult is 40-65 cm long and weighs 7-10 kg. Some occasionally weigh up to 17 kg. Males are larger than females. The pelage is thick, with coarse guard hairs overlying the underfur. The soft dense underfur (the commercially valuable pelt called "nutria") is about 2 cm long on the belly, and 2-5 cm long and less dense on the back. The color is yellowish to reddish brown on the back and pale yellow on the belly.
The coypu is distributed through southern Brazil, Paraguay, Uruguay, Bolivia, Argentina, and Chile. It has been widely introduced in North America, Europe, northern Asia, and eastern Africa. As a result of escapes and releases from fur farms, the animals are now feral in Europe, North America, northern Asia, Japan, and East Africa. In the United States, they are abundant in Louisiana, Oregon, Florida, and the Chesapeake Bay region.
In various countries, the animal's status ranges from that of a rarity to that of a pest. Wild coypu are protected by law in Argentina because of overhunting, but there are about 100 producers of farmed coypu.3 Elsewhere the animals are destroyed en masse to reduce the threat of damage to irrigation ditches, dams, and agricultural crops. In England a decade-long program has eradicated them.
HABITAT AND ENVIRONMENT
Coypu mainly inhabit the banks of fresh or brackish waterways.4 They live in temperate zones and are highly sensitive to freezing conditions. Also, their heat tolerance is poor; lowland tropical regions may be too hot for them.
The coypu feeds mainly at night. The diet consists chiefly of plants, particularly water plants and reeds. Large amounts of fibrous vegetation is decomposed in the cecum, where bacteria break down cellulose particles. Mussels, snails, and other small organisms are also often eaten.
The animals burrow into soft soil or construct nests out of vegetation above ground.
Coypu are relatively fast breeding. Females first give birth at ages ranging from 6 to 15 months. From then on, they produce 2 or 3 litters a year. They are able to mate and give birth at any time of the year, although more young are born during certain seasons. The gestation period is between 128 and 140 days. There are 5 or 6 (sometimes up to 12) young in each litter. Newborns are well developed, able to see, and fully covered with hair at birth.
The female's four or five pairs of mammae are located on the side of the body, an adaptation that permits the young to nurse while floating with their mothers in the water. In captivity, young are nursed for two months, but can survive if weaned at five days. The mean body weight at birth is about 225 g, but growth is rapid during the first five months.
Coypu have a potential life span of more than six years. However, they seldom survive more than three years, and in the wild probably no animals are older than five years.
These are passive creatures, usually entirely lacking in aggression. They are shy and fearful; the slightest disturbance will send them scurrying to the shelter of water, a burrow, or other hiding place. With their large incisors they can bite viciously, but in captivity they tame down, even to where they can be carried around by hand. Compared with domestic animals, they are very sanitary in their feeding and living habits.
In hot climates they are nocturnal, in cooler climates crepuscular, and in cold weather they become diurnal. Captive animals become conditioned to diurnal activity if fed during daylight hours. Most of the active period is spent feeding, grooming, and swimming. Grooming is done by scratching and "nibbling" the fur, and an oily secretion from glands located near the mouth and anus lubricates the pelage. Secretions from the anal glands are also employed for marking out territory.
Excellent swimmers, coypu spend most of their time in the water. They can remain submerged for five minutes or more. On land, they lumber about with awkward, clumsy movements; however, when the need arises they can run fast and jump short distances.
Although they usually live together in pairs, coypu will form large colonies. They tend to remain in one area throughout their lives: their daily "cruising range" has been measured at less than 45 m.5 However, drought or freezing weather can induce mass migrations.
The burrows, which are dug in sloping banks, are usually short with no branching tunnels and generally end in a simple chamber.
In South America, the coypu has a long history of use. Nutria fur was in such high demand and the animal was hunted so avidly at the beginning of the last century that it became rare and had to be protected by government decree. As a result, populations increased dramatically. Nowadays, coypu are protected in many areas, but widespread poaching has reduced their numbers and range.
Many thousands are killed each year just for the guard hairs, which are used in making felt.
Coypu are used in marsh management to reduce infestations of aquatic weeds and to keep waterways open.
In most areas where it is found, the coypu is trapped by commercial hunters. However, as noted, several countries have coypu farms. In Germany, the animals have been raised on diets consisting chiefly of potatoes supplemented with oats, clover, corn, hay, green forage, legumes, turnips, or cabbage. Elsewhere, feeds generally include such materials as hay, corn, crushed oats, greens, root vegetables, apples, bread, and rabbit feed.
To confine coypu, a wall of stone or concrete or a fence of stout wire netting is necessary. It must be set 1 m deep into the ground and rise 1-1.5 m above ground. Water must be available.
Where selected strains of animals are kept, it is usual to house each female in separate small compartments, complete with pools and shelter boxes. Each is then paired with a male, which is removed after mating to leave the female to rear her brood in seclusion.
The fur is particularly valuable because the female's nipples are so high that the soft belly fur is unbroken.
This herbivore is much cheaper to feed than the furbearing carnivores such as mink. Furs of coypu raised in captivity fetch a price about three times greater than furs from wild animals.6
Wherever the coypu has escaped it has damaged embankments and stream banks. The burrows sometimes weaken dikes that protect low lying areas from flooding. In northern Europe and eastern England, for example, it is considered a serious pest. In rice paddies, coypu could become particularly devastating. They can also damage crops and natural plant communities.
Coypu can carry viruses that result in toxoplasmosis, papillomatosis, rabies, and equine encephalomyelitis; bacteria that cause salmonellosis, paratyphoid, and leptospirosis; protozoans that produce sarcosporidiosis and coccidiosis; and rickettsia. Common diseases of captive specimens are bacterial pneumonia, hepatitis-nephritis, Strongyloides infection, and neoplasms.
European winters often cause the coypu's tail (which is hairless) to freeze, but the animal hardly seems to notice. A more dangerous situation arises when lakes, streams, or rivers freeze over; beneath the ice, coypu cannot find their way as easily as beavers, and often drown.
RESEARCH AND CONSERVATION NEEDS
Little research needs to be done. There is massive literature on farming coypu. Nonetheless, the animal's behavior is little studied, and there are few reliable published observations on its social organization.
18 Giant Rat[edit | edit source]
The giant rat, also known as the pouched rat, is one of Africa's largest rodents.! Two species have been distinguished: Cricetomys gambianus, which lives chiefly in savannas and around the edges of forests and human settlements; and Cricetomys emini, which occurs mainly in rainforests. Both are highly prized as food
These animals are solitary, but they are easy to handle, have a gentle nature, and make good pets. Researchers at the University of Ibadan in Nigeria have been developing techniques for managing them in captivity. Breeding stocks were established in 1973, and since then so many generations have been bred that this small population is considered domesticated. Commercial-scale giant rat farming is now being established in southern Nigeria.
This is a promising development because giant rats are a common "bushmeat" throughout much of Africa. Since these herbivores are well known there, and are acceptable as food, they may have as much or more potential as meat animals than the introduced rabbits that are getting considerable attention (see page 178).
AREA OF POTENTIAL USE
The intertropical zone of Africa from the southern Sahara to the northern Transvaal.
APPEARANCE AND SIZE
This species is among the most striking of all African rodents.
Because of its large size, it often causes amazement - even alarm - when seen for the first time. The body measures as much as 40 cm, and, on average, weighs about 1-1.5 kg. The record for a hand-reared specimen is 1.6 kg 2
Apart from its size, the best known species (Cricetomys gambianus) is noted for the dark hair around its eyes, a nose that is sharply divided into dark upper and pale lower regions, and a tail that has a dark (proximal) section and pale (distal) section. The overall body color is a dusky gray.
The lesser known species (Cricetomys emini) has short, thin, and relatively sleek fur. Its upper parts are pale brown; the belly is white.
Giant rats are commonly found from Senegal to Sudan, and as far south as the northern region of South Africa. The main species is mostly found in moist savannas, patches of forests, and rainforests. However, it can also be found in all West African vegetation zones from the semiarid Sahel to the coast. It also exists at high altitudes- up to about 2,OOO m in West Africa and 3,000 m in eastern Africa.
The rainforest species occurs in the great equatorial forest belts of Zaire and neighboring Central African countries.
These animals are probably not threatened with extinction. However, they have been exterminated in some areas (such as in parts of eastern Zaire) where the human population is dense, the land fully cultivated, and the wildlife overhunted. Although common, they are not as well known as one might suppose from their bulk and from the fact that they are sometimes found around, and even inside, houses.
HABITAT AND ENVIRONMENT
Giant rats occur largely in lightly wooded dryland regions or in forested humid regions. They cannot tolerate high temperatures or truly arid conditions. They often live in farm areas and in gardens. Their burrows are commonly found inside deserted termite mounds and at the base of trees. Some have also been found in the middle of cassava fields.
These are herbivores with a tendency to omnivory. They prefer fruits, but also subsist on tubers, grains, vegetables, leaves, legume pods, and wastes (such as banana peels). However, they are not grasseaters. Giant rats also kill and eat mice, insects (caterpillars, cockroaches, and locusts, for example), and probably many other small animals.3 They are particularly fond of mollusks (such as snails).
Reproduction is prolific and year-round. The female attains puberty at 20-23 weeks and the gestation period is about 20-42 days. The young are weaned at 21-26 days of age but stay with their mother until 2-3 months of age. So far, the record for the most litters has been 5 in 9 months. It thus seems possible that a female can reproduce 6 times a year. Litter size ranges between I and 5, but 4 is most common. Thus, in 1 year a single female could produce 24 or more young.
These strictly nocturnal animals usually lead solitary lives and forage alone. Mostly, they occupy a burrow by themselves, except when the
young are being raised. The burrows can be complex. Below the entrances are vertical shafts leading to a system of galleries and chambers for storing food, depositing droppings, sleeping, or breeding. The home range is individual and limited (1-6 hectares). In the wild, one male "supervises" the home ranges of several females.
In captivity, the animals are often seen sitting up and ramming large amounts of food into their spacious cheek pouches. With full cheeks, they return to their burrows and disgorge the food into a "larder." Food (chiefly hard nuts) is stored there.
They swim and climb well.
A study carried out in Nigeria showed that the giant rat produces about the same amount of meat as the domestic rabbit.4 The meat's nutritional value compares favorably with that of domestic livestock, and African villagers know how to preserve it by smoking or by salting.
The giant rat has recently attracted attention as a potential laboratory animal.
Farmers in Nigeria have traditionally trapped the juveniles and fattened them for slaughter. They usually keep the animals in wire cages and feed them daily with food gathered in the wild as well as with scraps from the household.
As noted, the program at the University of Ibadan indicates that the giant rat can be domesticated. Already, specimens are being bred and reared in an intensive program. They adapt to captivity after about a month. They are subsequently transferred into breeding cages, which are wooden boxes with a rectangular wire-mesh "playroom." Each cage holds a breeding pair or a nursing female with its young. Experimental feeding cages have also been designed.5
Food-preference trials show that palm fruits and root crops (especially sweet potato) are preferred to grains and vegetables. Nutritional studies show that the animals can tolerate up to 7 percent crude fiber in their rations. Although largely vegetarian, they eagerly consume dry and canned dog food.
These animals have several advantages:
· They are well known and much sought after for food.
· They have adapted to life in lowland tropics.
· They are able to live on locally available plant materials, including vegetable waste.
· They reproduce rapidly.
· They are more tolerant of captivity than the grasscutter (see next chapter). This is largely because omnivorous feeding makes them easier to feed than the grasscutter and other strict herbivores.
This species could easily become a pest. It is recommended for rearing only in areas where it already exists. The crops it damages include cacao, root crops, peanuts, maize, sorghum, vegetables, and stored grains and foods. There is also the possibility that this rodent may transmit diseases to humans.
A project at the University of Kinshasa in Zaire reports problems in getting giant rats to reproduce in captivity. When two specimens were paired they sometimes fought so viciously that copulation was impossible.6 Special management may be required, such as housing animals in adjacent cages before actually introducing them to each other. Moreover, selection for docility may also be necessary.
The ratlike appearance is not attractive, and a few African tribes have taboos against consuming the meat of these animals.
RESEARCH AND CONSERVATION NEEDS
Throughout Africa south of the Sahara, giant rat domestication deserves experimentation and trials. Success would open up the potential for supplemental meat supplies in rural and urban areas where meat is now scarce. Tests are needed to determine the factors that favor breeding: temperature, aeration, light, privacy, and size and form of cages. Moreover, diets that are cheap and easy to make from local feedstuffs must be identified.
Further research on the domestication of the giant rat might include:
· Identifying husbandry techniques that are applicable at low cost in rural areas;
· Studying food digestibility and setting up various diets;
· Illuminating social behavior: pairing of animals, the best moment for pairing, duration of pairing, age of partners;
· Outlining the basics of husbandry (for instance, capital costs, food conversion ratios, growth rates) and making simple and cheap cages;
· Studying biology (anatomy, physiology, birth records, growth rate); and
· Testing the practical likelihood that this rodent may transmit diseases to people and other animals.
The giant rat has an interesting commensal relationship with Hemimerus, an insect that feeds on secretions in the skin. It seems to cause no irritation or damage, and may even benefit the host by helping to keep the skin clean. Caging these animals results in the general loss of the insect, but attempts should be made to maintain them and to determine their role and life cycle.7
The potential of this species as a laboratory animal in nutritional, clinical, and pharmacological research also deserves exploration.