Damaraland mole rat (Cryptomys damarensis)
Like other blesmols, the Damaraland mole-rat has a cylindrical body with short, stout limbs, large feet, and a conical head. It is also similar in size to most other African mole-rats, having a head-body length of 14 to 20 cm (5.5 to 7.9 in), with a short, 2 to 3 cm (0.79 to 1.18 in), tail, and weighing between 100 and 280 grams (3.5 and 9.9 oz). There are no external ears, and the blue-coloured eyes are tiny with thick eyelids. The incisor teeth are large and prominent, with flaps of skin behind them to prevent soil from falling into the throat while the animal is using them to dig.[4]
The fur is short and thick, and varies from fawn to almost black, with shades of brown being most common. There is always a white patch on the top of the head, although its exact shape varies, and there may also be additional blotches of white fur elsewhere on the body. Longer, sensory, hairs project above the fur over much of the body, with the facial whiskers being particularly long. Females have six teats.
Although named specifically for Damaraland, the mole-rats are found across much of southern Africa, including Botswana, Namibia, South Africa, Zambia, and Zimbabwe.[1] They are inhabit warm, semi-arid environments dominated by savannah scrubland or sandy grasslands. They are most common in association with red Kalahari psamments, and are found only where there is a sufficient supply of plants with subterranean storage organs.
Damaraland mole-rats are herbivorous, feeding solely on tubers, corms, and bulbs. Favoured foods include such plants as Acanthosicyos, Star-of-Bethlehem, Ledebouria, and Talinum. Their natural predators include mole snakes, and occasionally other local snakes, such as cobras.[4] They do not drink, obtaining all their water from their food, which is also an important source of minerals. Unlike most other mammals, they can effectively metabolise these minerals without access to vitamin D, which they lack because they are normally never exposed to sunlight.[5] The basal metabolic rate of Damaraland mole rats is also unusually low for mammals of their size, at just 0.66 cm3 O2 / g · h.[4]
Despite living in an entirely subterranean environment, Damaraland mole-rats exhibit circadian rhythms, and are active primarily during the day.[6] Their levels of the hormone melatonin can be altered by artificially changing the length of apparent daylight, suggesting that they are at least able to distinguish light from dark, although their eyesight may otherwise be very poor.
As eusocial animals, only the breeding pair within a colony is capable of reproduction. Non-reproductive individuals are not truly sterile, however, and become capable of reproduction if they establish a colony of their own. The reproductive systems of non-reproductive females are underdeveloped, with small, unvascularised uteri and tiny ovaries that contain undeveloped germ cells, but which are incapable of ovulation.[4] Non-reproductive males have smaller testes than their reproductive counterparts and produce little, if any, viable sperm.[16] The non-reproductive status of other adults is maintained by the presence of the breeding female.[17] While her removal causes previously non-reproductive females to become fully fertile, they will only mate with unrelated males, thus avoiding incest within the colony.[18]
The breeding female initiates courtship by calling and drumming with her hind feet. The pair then chase each other in a right circle before mating. Mating occurs frequently over a ten-day period, and gestation lasts 78 to 92 days.[19] Females can produce up to three litters of one to six pups per year.[17] The pups are initially hairless, with closed eyes, and only weigh 8 or 9 grams. They are weaned after 28 days, and reach adult size after around 14 months.
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