The Damaraland mole-rat (''Fukomys damarensis''), Damara mole rat or Damaraland blesmol, is a burrowing

rodent Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are n ...

found in southern

Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area ...

. Along with the smaller, less hairy, naked mole rat, it is a species of

eusocial Eusociality (from Greek εὖ ''eu'' "good" and social), the highest level of organization of sociality, is defined by the following characteristics: cooperative brood care (including care of offspring from other individuals), overlapping gen ...

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

Description

Like other

blesmol The blesmols, also known as mole-rats, or African mole-rats, are burrowing rodents of the family Bathyergidae. They represent a distinct evolution of a subterranean life among rodents much like the pocket gophers of North America, the tuco-tu ...

s, 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 , with a short, , tail, and weighing between . There are no external ears, and the blue-coloured eyes are tiny with thick eyelids. The

incisor Incisors (from Latin ''incidere'', "to cut") are the front teeth present in most mammals. They are located in the premaxilla above and on the mandible below. Humans have a total of eight (two on each side, top and bottom). Opossums have 18, wher ...

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. 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.

Distribution and habitat

Although named specifically for

Damaraland Damaraland was a name given to the north-central part of what later became Namibia, inhabited by the Damaras. It was bounded roughly by Ovamboland in the north, the Namib Desert in the west, the Kalahari Desert in the east, and Windhoek i ...

, the mole-rats are found across much of southern Africa, including

Botswana Botswana (, ), officially the Republic of Botswana ( tn, Lefatshe la Botswana, label= Setswana, ), is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory being the Kal ...

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

Zambia Zambia (), officially the Republic of Zambia, is a landlocked country at the crossroads of Central, Southern and East Africa, although it is typically referred to as being in Southern Africa at its most central point. Its neighbours are t ...

, and

Zimbabwe Zimbabwe (), officially the Republic of Zimbabwe, is a landlocked country located in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Botswana to the south-west, Zambia to the north, and ...

. They inhabit warm, semi-arid environments dominated by savannah scrubland or sandy grasslands. They are most commonly associated with red Kalahari psamments, and are found only where there is a sufficient supply of plants with subterranean

storage organ A storage organ is a part of a plant specifically modified for storage of energy (generally in the form of carbohydrates) or water. Storage organs often grow underground, where they are better protected from attack by herbivores. Plants that have ...

Biology

Damaraland mole-rats are herbivorous, feeding solely on

tuber Tubers are a type of enlarged structure used as storage organs for nutrients in some plants. They are used for the plant's perennation (survival of the winter or dry months), to provide energy and nutrients for regrowth during the next growing ...

corm A corm, bulbo-tuber, or bulbotuber is a short, vertical, swollen underground plant stem that serves as a storage organ that some plants use to survive winter or other adverse conditions such as summer drought and heat (perennation). The word ' ...

s, and

bulb In botany, a bulb is structurally a short stem with fleshy leaves or leaf basesBell, A.D. 1997. ''Plant form: an illustrated guide to flowering plant morphology''. Oxford University Press, Oxford, U.K. that function as food storage organs dur ...

s. Favoured foods include such plants as ''

Acanthosicyos ''Acanthosicyos'' is a genus of thorny shrubs of the botanical family Cucurbitaceae, subfamily Cucurbitoideae. The genus name derives from the Greek words "''akantha''" for thorn and "''sykios''" for cucumber or gourd. Species Endemic to the Na ...

'', Star-of-Bethlehem, ''

Ledebouria ''Ledebouria'' is a genus of African bulbous perennial herbs in the Asparagus family, Asparagaceae, subfamily Scilloideae. Most members were previously part of the genus ''Scilla''. A number of species are grown by cacti and succulent enthusiast ...

'', and '' Talinum''. Their natural predators include

mole snake The mole snake (''Pseudaspis cana'') is a species of snake. It has been placed in the family Lamprophiidae, and more recently in the family Pseudaspididae, along with the genus '' Pythonodipsas''. It is native to much of southern Africa, and i ...

s, and occasionally other local snakes, such as cobras. 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 Vitamin D is a group of Lipophilicity, fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects. In humans, the most important compounds in this group ar ...

, which they lack because they are normally never exposed to sunlight. The

basal metabolic rate Basal metabolic rate (BMR) is the rate of energy expenditure per unit time by endothermic animals at rest. It is reported in energy units per unit time ranging from watt (joule/second) to ml O2/min or joule per hour per kg body mass J/(h·kg). P ...

of Damaraland mole rats is also unusually low for mammals of their size, at just 0.66 cm³ O₂ / g · h. Despite living in an entirely subterranean environment, Damaraland mole-rats exhibit

circadian rhythm A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., endogenous) and responds to ...

s, and are active primarily during the day. Their levels of the hormone

melatonin Melatonin is a natural product found in plants and animals. It is primarily known in animals as a hormone released by the pineal gland in the brain at night, and has long been associated with control of the sleep–wake cycle. In vertebrat ...

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.

Behaviour

Damaraland mole-rats live in networks of tunnels,Naked and Not: Science News Online, June 24, 2006
/ref> which they dig with their front teeth. The tunnels are in diameter, and may stretch for up to . They have no connection to the surface, although their presence can be inferred from dome-shaped

molehill A molehill (or mole-hill, mole mound) is a conical mound of loose soil raised by small burrowing mammals, including moles, but also similar animals such as mole-rats, and voles. The word is first recorded in the first half of the 15th century. ...

s of excavated earth pushed up to the surface. As a result, the tunnels develop their own

microclimate A microclimate (or micro-climate) is a local set of atmospheric conditions that differ from those in the surrounding areas, often with a slight difference but sometimes with a substantial one. The term may refer to areas as small as a few squ ...

, containing warm, moist air, with low oxygen levels. Most digging occurs after rainfall, since dry soil is too difficult to excavate. Because they live in arid environments, this means that Damaraland mole-rats can be extremely active over short periods; a typical colony has been estimated to excavate three tons of soil over a two-week period. The burrow system consists primarily of foraging tunnels, which the rats dig in search of food. While particularly large tubers and bulbs are at least partially eaten where they are found, smaller ones are dragged to food storage chambers beneath the foraging tunnels. The foraging tunnels are typically only beneath the soil surface, but are connected to a smaller number of deep tunnels that lead down to the storage chambers,

latrine A latrine is a toilet or an even simpler facility that is used as a toilet within a sanitation system. For example, it can be a communal trench in the earth in a camp to be used as emergency sanitation, a hole in the ground ( pit latrine), or ...

s, and a central nest that may be as much as underground. Each burrow system is inhabited by a single colony of mole rats, typically with about twelve members, although colonies can range from as little as two to as many as forty members. The colony is

, consisting of a single breeding pair and their non-reproductive offspring. The non-reproductive members of the colony spend their time foraging and maintaining the tunnel system, in particular closing any breaches that may occur. Intruders from other colonies are generally rejected, although DNA paternity studies show that at least some non-reproductive members of a colony may have been fathered by outsiders. The colony has a clearly defined hierarchy, with the breeding male dominant, followed by the breeding female, then non-reproductive males, and finally non-reproductive females. Colonies fragment if the breeding female dies, with most surviving members dispersing to new locations. Particularly large individuals may also leave the colony to establish a new burrow system. In such cases, dispersal usually only occurs during rainy weather, ensuring that digging will be relatively easy once a suitable location has been found. New colonies are established by unrelated males and females, which become the new breeding pair. Dispersing individuals travel above ground, and are therefore vulnerable to predation from a wide range of animals; some studies have shown that only around 10 percent of dispersing individuals are later found in new colonies. For example, while small groups of siblings may sometimes leave a burrow system at the same time, normally only one survives to found a new colony. The Damaraland mole-rat is less vocal than the naked mole-rat, making only some birdlike chirps.

Reproduction

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 cell Germ or germs may refer to: Science * Germ (microorganism), an informal word for a pathogen * Germ cell, cell that gives rise to the gametes of an organism that reproduces sexually * Germ layer, a primary layer of cells that forms during embr ...

s, but which are incapable of

ovulation Ovulation is the release of eggs from the ovaries. In women, this event occurs when the ovarian follicles rupture and release the secondary oocyte ovarian cells. After ovulation, during the luteal phase, the egg will be available to be fertilize ...

. Non-reproductive males have smaller

testes A testicle or testis (plural testes) is the male reproductive gland or gonad in all bilaterians, including humans. It is homologous to the female ovary. The functions of the testes are to produce both sperm and androgens, primarily testoste ...

than their reproductive counterparts and produce little, if any, viable sperm. The non-reproductive status of other adults is maintained by the presence of the breeding female. 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. 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. Females can produce up to three litters of one to six pups per year. 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.

Genetics

The Damaraland mole-rat's

karyotype A karyotype is the general appearance of the complete set of metaphase chromosomes in the cells of a species or in an individual organism, mainly including their sizes, numbers, and shapes. Karyotyping is the process by which a karyotype is disce ...

shows 74 or 78 chromosomes ( 2n). Its fundamental number is 92.