Tenrecs

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Tenrecs

Tenrecs are four-legged nocturnal mammals belonging to the order Insectivora. Tenrecs have evolved into more distinct forms than any other family of animals

within the order. Tenrecs can resemble hedgehogs, moles, shrews, or muskrats, depending on the species. Some species of tenrecs have a long tail and long hind legs, while others have a stumpy tail and short hind legs. Furthermore, some species of tenrec have a spiny coat, similar to that of hedgehog, while others have velvety fur.

Within the order Insectivora, there are six general types: shrew type, rat type, hedgehog type, mole type, jeroba type, and otter type. Tenrecs are grouped together with the shrews, and are characterized by an elongated body, and long, pointed snout. Tenrecs belong to the family Tenrecidae.

Evolution of insectivores

Insectivores are the most primitive of all higher mammals, and insectivore like animals predated all of the orders of today’s mammals. The fossil remains of insectivores indicated that they lived during the Cretaceous period. Rat-sized ancestors of today’s insectivores date even back further—to the Jurassic and Lower Cretaceous periods. These fossils also indicate that tenrec-like animals and golden moles are related to each other.

Family tenrecidae

The family Tenrecidae includes about 27 species, all but three of which live on the island of Madagascar. The remaining three species (all otter shrews) live in central and west equatorial Africa.

In general, tenrecs have poor vision, but their senses of smell, hearing, and touch are acute. Like other insectivores, they have an elongated snout, a small, primitive brain, and their skull is relatively small, long, and narrow. Their fur can be soft, coarse, or even spiny. Tenrecs have retained some reptilian characteristics, such as a cloaca-like common chamber into which their digestive, reproductive, and urinary systems empty, and from which these substances leave their body.

The family Tenrecidae family includes four subfamilies: the Tenrecinae (spiny tenrecs), the Oryzorictinae (shrew and rice tenrecs), the Geogalinae (large-eared tenrecs), and the Potamogalinae (otter shrews). The best known tenrecs are similar in appearance to hedgehogs, and belong to the Tenrecinae subfamily. This subfamily includes four genera and four species. The rice tenrecs have a long tail and are closely related to the spiny tenrecs; this subfamily includes two genera and 19 species. There is one genus and one species in the subfamily Geogalinae and two genera and three species of otter shrews.

Common or tail-less tenrec (Tenrec ecaudatus)

The common tenrec is, perhaps, the best known species of tenrec. Vaguely resembling a hedgehog, it measures about 12.5 in (32 cm) long, with a stubby tail measuring 0.4-0.6 in (1-1.6 cm) in length. It has a long snout and coarse, bristly fur interspersed with spines. These tenrecs prefer sandier environments, such as highland plateaus and cliffs along riverbanks. During the day, these animals rest in crevices or burrows; at night, they forage for food by digging with their claws and snout. Common tenrecs mainly eat insects, lizards, eggs, roots, and fruit. In the dry season, these tenrecs hibernate in deep underground burrows. At the beginning of October, after a long hibernation, they mate. Female common tenrecs commonly have as many as 16 surviving offspring.

If threatened, common tenrecs stand on their hind legs and bristle their coats, and try to push the bristles into the intruder, while snorting, grunting, and hissing. Although common tenrecs are protected by law, the people of Madagascar hunt these animals for their fatty meat.

Rice tenrecs (Oryzorictes spp.)

The short-haired rice tenrecs have bodies that measure 1.5-5 in (4-13 cm), and their tails measure 1-6.5 in (3-16 cm). These tenrecs acquired their name because they live on and within the banks of rice paddies, as well as in warm, moist forests, swamps, and meadows. Their front limbs are well adapted for digging and these tenrecs spend a great deal of time underground. Rice tenrecs are only seen above ground at night, but it is assumed that they are very active during the day underground, eating invertebrates and crustaceans. Rice growers in Madagascar consider rice tenrecs to be pests.

Reproduction

some species of tenrec are prolific. Tenrecs produce the most young per litter (averaging between 12 and 15) of all the world’s mammals. The number of offspring can be even higher; for example, common tenrecs have been known to have as may as 32 young in one litter. Because female tenrecs almost always have multiple births, they have numerous nipples to feed their young. In fact, common tenrec females have 32-36 nipples.

Female tenrecs must sometimes forage for food in daylight, when the danger presented by predators is the highest, to adequately nourish themselves, so that they are able to meet the huge demand for milk. In some tenrec species, the young have extra camouflage to protect themselves from predators, which they lose as they mature. Young tenrecs are fairly independent creatures; they are able to run soon after they are born. By the time they are four weeks old, they are completely independent.

Temperature regulation

The body temperature of tenrecs is maintained between 78.8–86°F (26–30°C). The activity levels of streaked tenrecs vary with the surrounding temperature. Increases in physical activity generate the extra body heat that they need to survive in colder conditions. On a normal day, with a daytime temperature of about 68°F (20°C), streaked tenrecs rest inside their burrows; by early evening, their activity level increases. At midnight, they start taking more frequent rests and, by dawn, they crawl back inside their shelters. However, when the outside temperature goes down to 60.8–64.4°F (16–18°C), tenrecs become much more active, both day and night. If the temperature gets colder than 60.8°F (16°C), even increased activity is insufficient to keep them warm, and they perish. Because the streaked tenrec inhabits moist areas with little temperature change, these animals rarely die of cold.

The habitat of common tenrecs, however, is much more variable than that of streaked tenrecs. On Madagascar, there is little rain in the winter, the land becomes very dry, and temperatures fall to as 50°F (10°C). At this point, common tenrecs, which have been accumulating fat all summer, roll into a ball and hibernate in their deep underground burrows for about six months. During hibernation, they are cold to the touch and breath about once every three minutes. During this time, they neither eat nor defecate.