Mammals

A fascinating species:

Last week we featured four species of mammals, some of which you may have already heard of. The animal kingdom has a wide variety of mammal species and we like to introduce you to a few more interesting mammals today... We will bring you more fascinating facts about the mammals featured so far along with many other new species in our future issues of Nature Trail.

Norwegian Lemming

The mammal with its own anti-freeze:

Most mammals have to increase heat production to maintain their body temperature when air temperatures fall below freezing point(0 degrees C, 32 degrees F), but lemmings do not begin to do so until the temperature reaches - 12 degrees C (12 degrees F).

Probably the only aboriginal mammal in Scandinavia, the Norwegian Lemming (Lemmus lemmus) is well adapted to life above the Arctic Circle. In order to reduce heat loss as much as possible, it grows a long winter coat that traps a layer of air in the underfur.

Lemmings tunnel under the snow to build burrows and nest chambers that are well protected. In a lemming nest, with a family in residence 60 cm (2 ft) below the snow surface, the temperature can reach 10 degrees C (50 degrees F) even when the outside temperature is below freezing. Lemmings are so dependent on snow to keep warm during winter that there are places where there is too little snow for them to live.

Lemmings are famous for their periodic migrations. At intervals that average three to four years, the lemming population reaches such a high density that many thousands of animals migrate in search of new habitats.

Their determination is such that they will cross busy roads and pass through large towns without stopping. The stories of lemmings drowning in large numbers when they reach the sea are however untrue.

Profile

Length: 80-170 mm (3.5-8.8 in).
Weight: 40-105 g (1.5-3.8 oz).
Distribution: Scandinavia.
Habitat: Sub-alpine tundra and marshy scrubland.
Breeding: A female can produce 2 litters of up to 5 pups each during a summer.
Diet: Herbs, grass.
Notes: Its skin is so loose that it can turn around in its tunnel inside its own skin.

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American Beaver - master builder among the mammals

Beaver dams are constructed from stones, tree stems, leaves and mud plastered together in layers to create a formidable structure. One was measured as being over 600 m (650 yds) long.

An entirely novel way (unusual) of life was evolved by the American Beaver (Castor canadensis). To avoid being caught by predators, beavers build 'lodges' in the middle of lakes and rivers. Each lodge, built out of mud, sticks and stones by a single pair and their offspring, is up to 1.8 m (6 ft) high and 12 m (39 ft) in diameter. It contains a central sleeping platform above water level. Every beaver lodge is built with several underwater entrances.

So long as the lodge is surrounded by water, the beavers' main predators, such as wolves, cannot get at them. In order to make sure that the water level around a lodge is deep enough for the underwater entrances to be below the ice during the winter freeze, the beavers build their famous dams. They also anchor logs under the water where they can be easily reached during the winter when the frozen pond surface traps them in their lodges.

Using their massive incisor teeth as chisels, beavers can fell trees up to 0.5 m (1.5 ft) in diameter. Chopped up into smaller sections, the trunks are brought down to the water's edge by the animals floating them along channels specially dug for the purpose.

Beavers have the ability to store oxygen in their tissues and this helps them to remain submerged for 15 minutes or more. To help them see better while underwater, their eyes are covered by a special membrane similar to that found in birds and reptiles.

Profile

Length: 0.7-1.3 m (2.3-4.2 ft), with a 215-300 mm (8.5-12 in) tail.
Weight: 9-32 kg (20-70 lb), with an average of about 13 kg (29 lb).
Distribution: Canada and northern USA; European Beaver may belong to the same species.
Habitat: Rivers and lakes in wooded areas.
Breeding: Mating in January-February, with a litter of 1-8 young born in April-May.
Diet: Bark, leaves and twigs of willow, aspen and birch.
Longevity: 19-20 years.
Notes: The beaver is one of the largest rodents in the world.

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Three-toed Sloth - the slowest mammal in the world

Each day, this lazy mammal spends 21 1/2 hours asleep. When active, it takes 6 1/2 hours to cover 1 mile (1.6 km) - more than 26 times slower than a walking man. The Three-toed Sloth (Bradypus tridactylus) adopted a life of almost perpetual (continuous) sleep in order to make itself less conspicuous (prominent) to predators.

The three great hooked claws on its hands (four on its feet) allow it to hang upside down in the upper branches of the tallest forest trees, where it avoids detection by looking like a bunch of dead leaves. Even when alert, its movements are so methodical and slow that it can actually swim faster than it can walk.

Hanging upside down is such a large part of its life that even its hair grows 'backwards' from the wrist towards the shoulder and from its stomach towards its back.

The sloth's lifestyle is so slow that other creatures have taken to living in its long matted fur.

Encouraged by the humid dampness of the tropical climate, algae grow in its fur and provide a food supply for a host of mites, beetles and moths. In order to reduce the amount of moving it has to do, this vegetarian animal has a massive stomach which it can fill with leaves which can then be digested slowly at its leisure.

The stomach and its contents when full account for 30 per cent of the animal's total body weight.

Profile

Length: 50 cm (20 in).
Weight: About 3.7 kg (8.1 lb).
Distribution: South America (Brazil north to Honduras).
Habitat: Forest.
Breeding: A single infant born after a gestation of 120-180 days.
Diet: Eats only the leaves of the cecropia tree.
Longevity: 11 years.
Notes: Has no front teeth; because the cheek teeth have no enamel, these teeth grow continuously throughout life to compensate for the heavy wear incurred by chewing fibrous leaves.

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Chinchilla- Owner of the warmest fur coat

Living at 3000-6000 m (10,000-20,000 ft) up in the Andes Mountains, Chile the Chinchilla needs a warm coat to survive. Its fur is the softest and densest of any known mammal.

The Chinchilla (Chinchilla laniger), the only species of its genus, is one of a number of small South American rodents adapted to life in desert habitats.

Living on one of the tallest mountain ranges in the world at altitudes where only the hardiest grasses and herbs will grow, the Chinchilla uses crevices (clefts) and holes in the bare rocky landscape as its burrows. With little water available in these arid high altitude deserts, it obtains all the moisture that it needs from herbs that store dew.

Its dense coat with its soft silky hair is so attractive that it soon became the most valuable fur for its size and weight.

A coat made only from the pelts (skins) of wild-caught animals once sold for US $100,000. The demand for their skins became so great that Chinchillas were wiped out from many parts of their range. In one year alone, 200,000 skins were exported from Chile.

Profile

Length: 225-380 mm (9-15 in), with a 75-150 mm (3-6 in) tail.
Weight: 0.5-1.0 kg (1.0-2.2 lb), females larger than males.
Distribution: South America from Bolivia to Chile.
Habitat: Semi-desert, rocky mountainside above 3000 m (10,000 ft).
Breeding: Up to 3 litters a year, each of 1-4 young.
Diet: Grasses and herbs.

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Nine-banded Armadillo

The only mammal with armour-plated protection

Hard bony plates cover the armadillo's body as a protection against predators. By flexing these plates and bracing its feet, it can also wedge itself in its burrow so firmly that it cannot be pulled out.

One of more than 20 species in the curious family of Dasypodidae, the Nine-banded Armadillo (Dasypus hovemcinctus) is one of the few species of South American mammals to have successfully invaded North America.

This has been possible only because of its ability to dig deep burrows, which it lines with grass and leaves. These provide the animal with a refuge in which to escape both the burning heat of the day and the intense cold of the desert night. The armadillo's powerful limbs are used to dig burrows up to 6 m (20 ft) long that can go as deep as 1.5 m (5 ft) below ground.

When digging, the forelimbs scrape and loosen the soil which is passed back to the hindfeet to be ejected from the burrow entrance by powerful kicks. To allow the hindlegs to work freely, the tail is braced on the floor of the tunnel in order to bear the animal's weight, raising the hindfeet clear of the ground.

Armadillos are excellent swimmers, but to avoid sinking under the weight of their armour, they have to swallow air to gain buoyancy. Armadillos are unique in giving birth to identical quadruplets. The four infants are produced from a single fertilised egg that subdivides once development starts.

Profile

Length: Up to 90 cm (3 ft), including a 30 cm (12 in) tail.
Weight: 5.5-7.7 kg (12-17 lb).
Distribution: South America from Argentina north as far as the southern USA.
Habitat: Semi-desert or arid grasslands.
Breeding: Up to 12 (but normally 4) young born in March-April.
Diet: Insects, molluscs, small amphibians, reptiles and carrion.
Longevity: 11 years in captivity.
Notes: Its acute sense of smell allows it to detect insects up to 12 cm (5 in) below ground.

Courtesy: Remarkable Animals