The question whether our common Guinea-pig is really the domesticated descendant of the animal just described can hardly be regarded as finally settled, and, indeed, independently of colour, there are sufficient differences between them to justify some doubt on the subject. The name Guinea-pig may, as Mr. Waterhouse suggests, be a mistake for Guiana-pig, and the first specimens may very probably have come from that part of America. Its prevalent colours, as is well known, are combinations of white, black, and yellow, and as these colours are shown in the drawings of Aldrovandus, dating back to within fifty years of the discovery of South America, there seems every reason to believe that the animal must have been long domesticated in America prior to its introduction into Europe. On the other hand, Dr. Rengger says that he saw fourteen Apereas representing the fifth or sixth generation from a single couple domesticated about seven years before, and that these exhibited no difference of colouring from the wild animal. Several allied species inhabit the great plains of South America.
The BOLIVIAN CAVY (Cavia boliviensis), which is grey in colour, with a faint yellowish tinge, with the throat and belly white, the feet whitish, and the incisor teeth orange yellow, inhabits the elevated parts of Bolivia, generally at a height of 10,000 or 12,000 feet. The ROCK CAVY (Cavia rupestris) is found in rocky districts in Brazil, where it shelters itself in holes and crevices. It is always found near the upper waters of rivers, and is a large species, measuring thirteen or fourteen inches in length. The SOUTHERN CAVY (Cavia australis), on the other hand, is a small species which inhabits Patagonia, where it ranges from 39° S. lat. to the Strait of Magellan.
This part of the world is also the abode of another and much larger species of the family, the PATAGONIAN CAVY or MARA (Dolichotis patachonica), an animal which somewhat resembles the Agouti in the length and comparative slenderness of its legs, and differs from all other Cavies in having tolerably long, pointed ears. It also possesses a very short tail. The molar teeth are rather small, and resemble those of the Guinea-pig in being formed of two nearly equal angular lobes, but the last molar in the upper jaw, and the first in the lower jaw, have three such lobes. The animal is somewhat Hare-like in its appearance, and has been mistaken for a Hare by superficial observers. It is, however, a much larger animal, measuring from thirty to thirty-six inches in length, and weighing from twenty to thirty-six pounds.
PATAGONIAN CAVY.
The Patagonian Cavy is clothed with a dense crisp fur of a grey colour on the upper part of the head and body, rusty yellow on the flanks, and white on the chin, throat, and belly; the rump is black, with a broad white band crossing it immediately above the tail. It inhabits Patagonia about as far south as 48°, and extends northwards into the La Plata territory as far as Mendoza. It is found only in the sterile desert part of the country, where the gravelly plains are thinly covered with a few stunted thorny bushes and a scanty herbage. The northern limit of the species, according to Mr. Darwin, is at the point where the vegetation of the plains becomes rather more luxuriant. The Patagonian Cavy usually burrows in the ground, but where it lives in the same region as the Viscacha, it will take advantage of the excavations made by that animal. It wanders to considerable distances from its home, and on these excursions two or three are usually seen together. Mr. Darwin says:—“It is a common feature in the landscape of Patagonia to see in the distance two or three of these Cavies hopping one after the other over the gravelly plains.” Their mode of running, on the same authority, more nearly resembles that of the Rabbit than of the Hare; though their limbs are long, they do not run very fast. They rarely squat like a Hare, but are very shy and watchful, and feed by day, in connection with which it is to be observed that the eyes are defended from the direct rays of the sun by well-developed eyelashes, which do not occur in the other Cavies. The female produces generally two young at a birth, which are brought forth and suckled in the burrow.
The CAPYBARA (Hydrochœrus capybara), the only other member of the present family, is the largest of all existing Rodents, large specimens measuring over four feet in length. It is a stout-built and massive animal, with limbs of moderate length, a large head with a very blunt muzzle, small eyes and ears, no tail, and both the fore and hind feet webbed. The upper incisor teeth have a broad and shallow groove down the front, and the molars present very remarkable characters. In the upper jaw the first three molars are each composed of two lobes united by cement, and on the outside of each of these lobes there is a fold of enamel which passes deeply into the tooth. The last molar consists of one lobe similar to those of the preceding teeth, but in place of the second there are ten or a dozen transverse plates. The first two molars of the lower jaw exhibit complex lobes and folds of enamel; the third and fourth a combination of folded lobes and transverse plates.
In its general form the Capybara is more pig-like than any of its relatives, and, indeed, its generic name, Hydrochœrus, Water-pig, recalls this resemblance, and at the same time intimates its aquatic habits. Its coat is composed of long and coarse hairs, often five or six inches long on the hinder parts, of a reddish-brown colour above, and a dirty brownish-yellow beneath. It is distributed over the whole eastern part of South America, from Guiana southwards to the Rio de la Plata, and ranges westwards into the lower parts of Peru and Bolivia.
MOLARS OF THE CAPYBARA.