The presence of these rodents at night is made known by their screaming cries.
The rodents are numerous and include several peculiar species.
The family, Chinchillidae, typified by the wellknown chinchilla, includes a small number of South American rodents with large ears and proportionately great auditory bullae in the skull, elongated hind-limbs, bushy tails, very soft fur and perfect clavicles.
In Africa the name of flying-squirrel is applied to the members of a very different family of rodents, the Anomaluridae, which are provided with a parachute.
In habits these rodents appear to be very similar to the true flying-squirrels.
In the order of Rodents squirrels are very numerous, and porcupines of two genera are met with.
Rodents are numerous, the mouse (111 - us sylvaticus) is very destructive, and beavers are met with in places.
In the latter are the coney, jerboa, several small rodents and the ibex.
MOLE-RAT, the name of a group of blind burrowing rodents, typified by the large grey Spalax typhlus of eastern Europe and Egypt, which represents the Old World family Spalacidae.
The bones of the bear, horse, rhinoceros, lion, elephant, hyena and of many birds and small rodents were unearthed.
Altogether 1621 bones, nearly all broken and gnawed, were found; of these 691 belonged to birds and small rodents of more recent times.
Arctic foxes feed largely on sea-birds and lemmings, laying up hidden stores of the last-named rodents for winter use.
Of the amphibious rodents, the pi-ea (Cavia aperea), mod, (C. rupestris), paca (Coelogenys paca), cutia (Dasyprocta aguti) and capybara (Hydrochoerus capybara) are noteworthy for their size and extensive range.
The typical genus Tragulus, which is Asiatic, contains the smallest representatives of the family, the animals having more of the general aspects and habits of some rodents, such as the agoutis, than of other ruminants.
The rodents are represented by an abundance of rats, with comparatively few mice, and by the ordinary squirrel, to which the people give the name of tree-rat (ki-nezumi), as well as the flying squirrel, known as the momo-dori (peach-bird) in the north, where it hides from the light in hollow tree-trunks, and in the south as the ban-tori (or bird of evening).
Anything the rodents may meet with on their journeys, such as thistle-stalks or bones, are collected and deposited on the viscachera.
Ecureuil), properly the name of the wellknown red, bushy-tailed British arboreal mammal, Sciurus vulgaris, typifying the genus Sciurus and the family Sciuridae, but in a wider sense embracing all the rodents included in this and a few nearly allied genera.
Besides chipped stone knives, the teeth of rodents, sharks, and other animals served an excellent purpose.
The European porcupine (Hystrix cristata) is the typical representative of a family of Old World rodents, the Hystricidae, all the members of which have the same protective covering.
These rodents are characterized by the imperfectly rooted cheek-teeth, imperfect clavicles or collar-bones, cleft upper lip, rudimentary first front-toes, smooth soles, six teats and many cranial characters.
The hamsters, of which there are several kinds, are short-tailed rodents, with large cheek-pouches, of which the largest is the common C. frumentarius.
The numbers of these destructive rodents are kept in check by foxes, dogs, cats and pole-cats, which feed upon them.
The cetacea and a few rodents are also without it.
Capybaras are aquatic rodents, frequenting the banks of lakes and rivers, and being sometimes found where the water is brackish.
Rodents may be characterized as terrestrial, or in some cases arboreal or aquatic, placental mammals of small or medium size, with a milk and a permanent series of teeth, plantigrade or partially plantigrade, and generally five-toed, clawed (rarely nailed or semi hoofed) feet, clavicles or collar-bones (occasionally imperfect or rudimentary), no canine teeth, and a single pair of lower incisors, opposed by only one similar and functional pair in the upper jaw.
In all rodents the upper incisors resemble the lower ones in growing uninterruptedly from persistent pulps, and (except in the hare group, Duplicidentata) agree with them in number.
Rodents include by far the greater number of species, and have the widest distribution, of any of the orders of terrestrial mammals, being in fact cosmopolitan, although more abundant in some parts, as in South America, which may be considered their headquarters, than in others, as in Australasia and Madagascar, where they are represented only by members of the mouse-group, or Myoidea.
All rodents are vegetable-feeders, and this uniformity in their food and in the mode of obtaining it, namely by gnawing, has led to that general uniformity in structure observable throughout the group; a feature which renders their classification difficult.
All rodents, with the sole exception of the dormice, have a caecum, often of great length and sacculated,, as in hares, the water-rat and porcupines; and the long colon in some, as the hamster and water-rat, is spirally twisted upon itself near the commencement.
The peculiar odour evolved by many rodents is due to the secretions of special glands, which may open into the prepuce, as in Mus, Microtus and Cricetus, or into the rectum, as in Arctomys and Thryonomys, or into the passage common to both, as in the beaver, or into pouches opening near the vent, as in hares, agoutis and jerboas.
The first family is represented by certain peculiar North American rodents known as sewellels, constituting the genus Haplodon (or Aplodon) and the family Haplodontidae and section Haplodontoidea.
Sewellels are medium-sized terrestrial rodents, with no postorbital process to the skull, which is depressed in form, and rootless cheek-teeth, among which the premolars number I, the first in the upper jaw being very small.
Finally, we have the marmots (Arctomys), which are larger and more heavily built rodents, with short ears, more or less short tails and rudimentary or no cheek-pouches.
The front root of the zygomatic arch is nearly vertical, and placed so far back that it is above the second molar, while the orbit - a unique feature among rodents - is almost completely surrounded by bone.
The few representatives of this group are all very small rodents, confined to tropical Africa, the Philippines and the Malay islands.
The second section, Castoroidea, of the present group includes only the family Castoridae, represented by the beavers, which are large aquatic rodents characterized by their massive skulls, devoid of post-orbital processes, with the angle of the lower jaw rounded, the molars rootless or semi-rooted, with re-entering enamel-folds, and one pair of premolars above and below.
- The next section, according to Prof. Max Weber's arrangement, is that of the Anomaluroidea, typified by the rodents commonly called African flying-squirrels (Anomaluridae), but better designated scale-tailed squirrels, or simply "scaly-tails," since one member of the family has no parachute.
Thomas places these rodents in the neighbourhood of the porcupines.
The grounds for referring the African jumpinghares (Pedetidae) to the Anomaluroidea rest largely on the evidence of certain Tertiary rodents from Europe, such as Issiodoromys.
Dormice a r e small arboreal rodents, with long hairy tails, large eyes and ears, and short fore-limbs, ranging over Europe, Asia and Africa.
These are small rodents with somewhat the appearance of the pigmy squirrels (Nannosciurus), which in some degree connect the family with the Muridae.
They are small rat-like rodents, with one pair of upper premolars, which are mere pins, as is the last molar, and the two pairs of limbs of normal length, with the metatarsals separate; the infra-orbital opening in the skull being triangular and widest below, while the incisive foramina in the palate are elongated.
The Dipodinae, on the other hand, are leaping rodents, with the metatarsals elongated, a small upper premolar present or absent, and the crowns of the molars tall.
They are the only rodents in that island.
Other allied African genera are Steatomys and Lophuromys, which include several species of small mouse-like rodents, with the habits of dormice generally, though some burrow in cornfields.
In the rodents now to be considered, the angular process of the lower jaw arises from the outer side of the sheath of the incisor.
The majority of these rodents, many of which are of large size, are terrestrial, but a few are burrowing, others arboreal and two or three aquatic.
The Old World porcupines, constituting the family Hystricidae, are terrestrial, stoutly built rodents, with limbs of subequal length in front and behind, and the skin covered with strong spines.
In the family Caviidae, typified by the cavies (or guinea-pigs), may be included a large number of South and Central American rodents, among which the agoutis and pacas are often ranked as a family (Dasyproctidae) by themselves.
Since these rodents walk more or less entirely on their toes, in such a manner that the edges of the claws or nails come in contact with the ground, these tend to assume somewhat of a hoof-like character; while the foot-pads are more or less horny.
All these rodents are remarkable for the manner in which the liver is divided into minute lobules.
The African cane-rats, Thryonomys, are large terrestrial rodents, ranging from the centre of the continent to the Cape, easily recognized by their deeply fluted incisors.
The more typical members of the family are rat-like burrowing rodents, living in communities.
The tapir, fox, deer, wild cat, wild dog, carpincho or water hog and a few small rodents nearly complete the list of quadrupeds.
The Rodents are also well represented by various squirrels, mice and hares.
The agouti and the armadillo are practically extinct and the only other mammals are ground squirrels, rats, a few other small rodents, and some bats.
Among the rodents there are hares, marmots, beavers, squirrels, rats and mice, the last in enormous swarms. Of the larger game the chamois and deer are specially noticeable.
There are six species of monkey corresponding to those of Guiana and the Amazon valley, the sloth and ant-eater, 12 known genera of rodents, including many species of Mures, the cavy, the capybara, the paca, the nutria, the agouti, the tree porcupine, Loncheres cristata, Echimys cayen and the Brazilian hare.
Cavies in general, the more typical representatives of the Caviidae, are rodents with hooflike nails, four front and three hind toes, imperfect collar-bones, and the cheek-teeth divided by folds of enamel into transverse plates.
The porcupine and a large Octodont rodent (Ctenodactylus), the jerboa (two species), the hare, and various other rodents are met with in Tunisia.
All authorities are agreed in dividing rodents into two great sections or sub-orders, the one, Duplicidentata, comprising only the hares, rabbits and picas, and the other, Simplicidentata, all the rest.