Golden mole

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Golden moles[1]
Temporal range: Early Miocene–Recent
[2]
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Afrosoricida
Suborder: Chrysochloridea
Broom, 1915
Family: Chrysochloridae
Gray, 1825
Genera

Golden moles are small, insectivorous burrowing mammals native to southern Africa. They form the family Chrysochloridae. They are taxonomically distinct from the true moles, which they resemble due to convergence. The golden moles bear a remarkable resemblance to the marsupial moles of Australia, so much so that, the marsupial/placental divide notwithstanding, arguments were once made that they were related, possibly because they are very primitive placentals and because of the many mole-like specializations.

Characteristics

Golden moles live almost exclusively underground, beneath grassveld, forest, swamps, deserts, or mountainous terrain. Like several other burrowing mammals with similar habits, they have short legs with powerful digging claws, very dense fur that repels dirt and moisture, and toughened skin, particularly on the head. Their eyes 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.[3]

They range in size from about 8 to about 20 cm. They have muscular shoulders and an enlarged third claw on the forelimbs to aid digging, with no fifth digit and vestigial first and fourth digits; the hind feet retain all five toes and are webbed to allow efficient backward shoveling of the soil loosened with the front claws. They feed on small insects, which are located with the sense of hearing. Grant's golden mole (Eremitalpa granti) can cover 6 km each night looking for food.[4]

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. During extremely hot weather, Grant's golden mole will retreat to depths of around 50 cm and enter a state of torpor, thus conserving energy.[4]

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.[3]

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.

Golden moles use a head-dipping behavior to detect the vibrations produced by grass mounts in order to position themselves within detection range of the head-banging alarms produced by their termite prey.[5]

Status

Of the 21 species of golden mole, no fewer 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

  1. ↑ Bronner, G. N.; Jenkins, P. D. (2005). "Order Afrosoricida". In Wilson, D. E.; Reeder, D. M. Mammal Species of the World (3rd ed.). Johns Hopkins University Press. pp. 77–81. ISBN 978-0-8018-8221-0. OCLC 62265494. 
  2. ↑ Savage, RJG, & Long, MR (1986). Mammal Evolution: an illustrated guide. New York: Facts on File. p. 53. ISBN 0-8160-1194-X. 
  3. ↑ 3.0 3.1 Kuyper, Margaret (1984). Macdonald, D., ed. The Encyclopedia of Mammals. New York: Facts on File. pp. 764–765. ISBN 0-87196-871-1. 
  4. ↑ 4.0 4.1 Piper, Ross (2007), Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals, Greenwood Press.
  5. ↑ Narins PM; Lewis ER; Jarvis JJUM; O’Riain J (1997). "The use of seismic signals by fossorial southern African mammals: a neuroethological gold mine". Brain Research Bulletin 44: 641–646. 
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