Definitions

lined nest

Golden mole

Golden moles are small, insectivorous burrowing mammals native to southern Africa. They form the family Chrysochloridae, and so are taxonomically distinct from the true moles. The golden moles bear a remarkable resemblance to the marsupial moles of Australia, so much so that, the marsupial/placental divide notwithstanding, they were once thought to be related.

Characteristics

Golden moles live almost exclusively underground, beneath grassveld, forest, swamps, deserts, or mountainous terrain. Like several other burrowing mammals with similar habits, have short legs with powerful digging claws, very dense fur that repels dirt and moisture, and toughened skin, particularly on the head. They retain eyes but they are non-functional and covered with skin and fur, the ears are just tiny openings, and, like the marsupial moles, they have an enlarged leather-like pad to protect their nostrils. Their primary sense is that of touch, and they are particularly sensitive to vibrations that may indicate approaching danger.

They range in size from about 8 to about 20 cm. They have muscular shoulders and an enlarged third claw to aid digging on the forelimbs, with no fifth digit and vestigal first and fourth; the hind feet retain all five toes and are webbed to allow efficient backward shoveling of the soil loosened with the front claws. It feeds off small insects , which it triangulates by using its tiny ears to listen to the sound of the long grass in the wind (its ears are natural geophones).

While the desert species simply 'swim' through loose sand, all other species construct permanent burrows. The burrows are relatively complex in form, and may penetrate as far as a metre below ground. They include deep chambers for use as bolt-holes, and others as latrines. Excavated soil is pushed up to the surface as ridges or mole-hills, or is compacted into the tunnel walls.

Females give birth to one to three hairless young in a grass-lined nest within the burrow system. Breeding occurs throughout the year. The adults are solitary, and their burrowing territory may be aggressively defended from intruders, especially where resources are relatively scarce.

Because these mammals were previously thought to have originated in Gondwana, golden moles used to be regarded as rather 'primitive' creatures: their low resting metabolic rate and their ability to switch off thermoregulation when inactive, however, are no longer regarded as indications that golden moles are undeveloped 'reptilian mammals', but rather as essential adaptations to a harsh climate. By going into a torpor when resting or during cold weather, they conserve energy and reduce their need for food. Similarly, they have developed particularly efficient kidneys and most species do not need to drink water at all. Like the tenrecs, they possess a cloaca, and males lack a scrotum.

Status

Of the 21 species of golden mole, no less than 11 are threatened with extinction. The primary causes are sand mining, poor agricultural practices, increasing urbanisation, and predation by domestic cats and dogs.

Classification

As with many groups, the classification of the golden moles is undergoing an upheaval at present in the light of the flood of new genetic information becoming available. They have traditionally been listed with the shrews, hedgehogs and a grab-bag of small, difficult-to-place creatures as part of the order Insectivora. Some authorities retain this classification, at least for the time being. Others group the golden moles with the tenrecs in a new order which is sometimes known as Tenrecomorpha, while others call it Afrosoricida and reserve Tenrecomorpha for the Tenrecidae family.

References

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