Animal Diversity Web

Diversity

Eurasian or Ukrainian blind mole-rats, the Spalacinae, comprise a relatively small subfamily of Old-World fossorial muroid rodents. There are 13 species in 1 genus, Spalax. (Musser and Carleton, 2005)

Geographic Range

The range of Spalacinae extends around the eastern portion of the Mediterranean and the Black Sea, from the Balkans through Ukraine, Asia Minor, Syria, Palestine, and into Egypt and Libya. (Carleton and Musser, 1984; Nowak, 1999)

• Biogeographic Regions
• palearctic
  • native

Habitat

Spalacines live in moderately dense sandy or loamy soils that receive more than 100 mm of annual rainfall. They range from below sea level to above 2,600 meters, and they inhabit upland steppes, mountain valleys, agricultural fields, orchards, woodlands, river and lake basins, grasslands, and brushy areas. (Carleton and Musser, 1984; Nowak, 1999)

• Habitat Regions
• temperate
• terrestrial

• Terrestrial Biomes
• savanna or grassland
• chaparral
• forest
• scrub forest

• Other Habitat Features
• agricultural
• riparian

Physical Description

Spalacines are chunky, molelike animals with short legs, small feet and claws, subcutaneous eyes, and external ears that have been reduced to tiny ridges. They range in length from 130 to 350 mm, and weigh 100 to 570 grams. There is no visibile tail. Mole rats have thick, soft fur that is nearly reversible, allowing the animals to easily back down tunnels. They have broad, cushioned snouts with which they pack earth into the walls of their burrows. There are stiff rows of tactile bristles running down either side of a mole rat's face. The fur color is brown, reddish, or yellowish gray, and the ventral parts are generally grayish or straw-brown. The front of a mole rat's head is paler than the rest of the body. The feet have a silvery sheen to them, and there are five digits on each foot.

The spalacine dental formula is 1/1, 0/0, 0/0, 3/3 = 16. The broad incisors are orthodont and project forward in front of the lips. The cylindrical cheekteeth are rooted and have an enamel pattern in the shape of a Z or an S. The rows of molars converge slightly posteriorly. The first two molars are about equal in size, and the third is slightly smaller. The jaw muscles, on which mole rats rely for digging, are extremely strong. Mole rats have heavy skulls and a wide rostrum, but the zygomatic arches are quite thin and delicate. The frontals are small and there are no supraorbital ridges. Adults usually have a sagittal crest. The thick-walled auditory bullae are somewhat inflated. Spalacines have 13 thoracic vertebrae and six lumbar vertebrae. The spalacine stomach is two-chambered and the cecum is divided into 18 to 20 chambers. There is no stapedial artery; rather, the infraorbital artery provides circulation to the orbits. Mole rats have a diploid chromosome number ranging from 38 to 62. (Carleton and Musser, 1984; Nowak, 1999)

• Other Physical Features
• endothermic
• homoiothermic
• bilateral symmetry

Reproduction

During the mating season, several males construct peripheral mounds around each female's breeding mound, and mating takes place within the breeding mound. Mole rats have elaborate courtship rituals. When a male and female encounter one another, they each assume a defensive posture and make a series of rushes at the other, attacking and then quickly retreating. The male emits a low-pitched growl, while the female gives a high-pitched cry. Then, if both animals are ready to mate, they begin licking and stroking one another, giving off soft trills. Finally, the male mounts the female from behind, and copulation begins. Copulation can last up to 90 minutes. However, when copulation is finished, the animals go their separate ways; spalacines are promiscuous and do not associate with the opposite sex for long. (Carleton and Musser, 1984; Harrison, 1972; Nowak, 1999)

• Mating System
• polygynandrous (promiscuous)

Mole rats usually breed just once a year, from November to March, and have their litters from January to April. Female mole rats breed for the first time when they are about two years old, and most females only have a single litter in their lifetime. Some do not breed at all. For those that do reproduce, gestation is about a month long. The litter size ranges from one to six, but is usually between two and four. The young grow fur when they are about two weeks old and leave their mother's nest at about four to six weeks. (Carleton and Musser, 1984; Nevo, 1999; Nowak, 1999)

• Key Reproductive Features
• semelparous
• seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual
• fertilization
• viviparous

Female mole rats build breeding mounds in which they mate and rear their young. Each mound can be up to 160 cm long by 135 cm wide and 40 cm high. Each has a nest chamber in the center. Inside, the female nurses her altricial young for about a month. Other than providing sperm, male mole rats make no investment in their offspring. (Carleton and Musser, 1984; Nowak, 1999)

• Parental Investment
• altricial
• pre-fertilization
  • provisioning
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • provisioning
    • female
  • protecting
    • female

Lifespan/Longevity

Spalacines have a maximum lifespan of four and half years in the wild, and an average lifespan of about three years. In captivity, mole rats have been known to live as long as 15 years. (Nevo, 1999; Nowak, 1999)

Behavior

Spalacines dig with their chisel-like incisors, pushing and packing earth with their broad snouts and kicking dirt out behind them with their hind feet. They build elaborate burrow systems with two levels of passageways: a top level for foraging, and and deeper level for living quarters. The top level passageways run 10 to 25 cm below the soil surface and can stretch for hundreds of meters. As mole rats dig these foraging tunnels, they push up mounds of earth that can stretch 500 cm wide. Mole rats also sometimes incorporate above-ground resting mounds into their burrow systems that connect to their foraging tunnels. The deeper passageways include one or two nest chambers, each about 20 to 30 cm wide and lined with plant material for bedding, and multiple chambers for food storage and excretion. These deeper chambers are usually 20 to 50 cm below the soil surface. However, mole rats dig even deeper during the hottest months of the year, when they are less active--they have been recorded as far 410 cm below the soil surface. Each mole rat burrow system displaces up to three tons of soil.

Mole rats are active at varying times of the day or night; they sometimes come above ground to forage under the cover of darkness. They are solitary, territorial, and aggressive towards intruders. The size of each mole rat's territory varies with the species, population, habitat, age, and sex. Population densities range from 0.1 to 23 mole rats per hectare. Most individuals in any given mole rat population are adults, and the sex ratio is skewed towards females. (Carleton and Musser, 1984; Nevo, 1999; Nowak, 1999)

• Key Behaviors
• fossorial
• diurnal
• nocturnal
• motile
• sedentary
• solitary
• territorial

Communication and Perception

Mole rats navigate their pitch-black subterranean environment by touch, and they also have acute hearing. Their middle ears are specially adapted to perceive low-frequency sounds, which travel well underground. Their sense of smell is thought to be relatively weak, but they do use pheromones to communicate and they can sniff out their food. They make a variety of grunting and hissing noises, especially when threatened. They locate one another during the mating season by rapidly drumming their heads against the ceilings of their burrows, creating seismic vibrations. (Nevo, 1999; Nowak, 1999)

• Communication Channels
• acoustic
• chemical

• Other Communication Modes
• pheromones
• vibrations

• Perception Channels
• tactile
• acoustic
• vibrations
• chemical

Food Habits

Spalacines are herbivores that eat mainly roots, bulbs and tubers. When they forage on the surface from time to time, they consume grasses, seeds, stems, acorns, and a few insects. They store large amounts of plant material in their underground chambers. (Carleton and Musser, 1984; Nowak, 1999)

• Primary Diet
• carnivore
  • insectivore
• herbivore
  • folivore
  • granivore

• Foraging Behavior
• stores or caches food

Predation

Owls are the most important predators on mole rats. To avoid predation, mole rats spend most of their time underground, and they can be aggressive when cornered. Also, their fur color is often correlated with soil color: mole rats in darker soils have darker fur, those in lighter soils have lighter fur. This suggests that visual predators exert a fair degree of selective pressure on mole rat populations. (Carleton and Musser, 1984; Nevo, 1999; Nowak, 1999)

• Anti-predator Adaptations
• cryptic

• Known Predators

  • owls (Strigiformes)

Ecosystem Roles

Mole rats probably help to aerate the soil with their extensive digging activity, and they are consumers of various plant species as well as prey for owls.

Economic Importance for Humans: Positive

There are no known positive impacts of spalacines on humans, except in their roles in healthy ecosystems they inhabit.

Economic Importance for Humans: Negative

Spalacines can become serious agricultural pests. (Carleton and Musser, 1984; Nowak, 1999)

• Negative Impacts
• crop pest

Conservation Status

The IUCN currently lists five of the 13 species in this family as vulnerable: sandy blind mole rats (Spalax arenarius), giant blind mole rats (or Russian blind mole rats, Spalax giganteus), Balkan blind mole rats (or Bukovin blind mole rats, Spalax graecus), greater blind mole rats (Spalax microphthalmus), and lesser blind mole rats (Spalax leucodon). (IUCN, 2004)

• IUCN Red List [Link]

  Not Evaluated

Other Comments

The earliest known spalacine fossil is about 25 million years old, from the lower Miocene of Greece. This makes Spalacinae the oldest subfamily within Spalacidae, at least in the fossil record. Molecular work is needed to clarify the divergence times between spalacines and other spalacid groups. The earliest known Spalax fossils are from the late Pliocene. Spalax arose in Eurasia, and did not colonize North Africa until the Pleistocene, between 70,000 and 35,000 years ago. (Nevo, 1999; Savic and Nevo, 1990)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Allison Poor (author), University of Michigan-Ann Arbor.

References

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Carleton, M., G. Musser. 1984. Muroid rodents. Pp. 289-379 in S Anderson, J Jones Jr., eds. Orders and Families of Recent Mammals of the World. New York: John Wiley and Sons.

Chaline, J., P. Mein, F. Petter. 1977. Les grandes lignes d'une classification évolutive des Muroidea. Mammalia, 41: 245-252.

Ellerman, J. 1940. The Families and Genera of Living Rodents, vol. I. London: British Museum (Natural History).

Harrison, D. 1972. The Mammals of Arabia, vol. 3. London: Ernest Benn Ltd..

IUCN, 2004. "2004 IUCN Red List of Threatened Species" (On-line). Accessed May 26, 2005 at www.redlist.org.

Jansa, S., M. Weksler. 2004. Phylogeny of muroid rodents: relationships within and among major lineages as determined by IRBP gene sequences. Molecular Phylogenetics and Evolution, 31: 256-276.

Michaux, J., A. Reyes, F. Catzeflis. 2001. Evolutionary history of the most speciose mammals: Molecular phylogeny of muroid rodents. Molecular Biology and Evolution, 18(11): 2017-2031.

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Musser, G., M. Carleton. 1993. Family Muridae. Pp. 501-753 in D Wilson, D Reeder, eds. Mammal Species of the World. Washington, D.C.: Smithsonian Institution Press.

Musser, G., M. Carleton. 2005. Superfamily Muroidea. D Wilson, D Reeder, eds. Mammal Species of the World. Washington, D.C.: Smithsonian Institution Press.

Nevo, E. 1999. Mosaic Evolution of Subterranean Mammals. Oxford: Oxford University Press.

Norris, R., K. Zhou, C. Zhou, G. Yang, C. Kilpatrick, R. Honeycutt. 2004. The phylogenetic position of the zokors (Myospalacinae) and comments on the families of muroids (Rodentia). Molecular Phylogenetics and Evolution, 31: 972-978.

Nowak, R. 1999. Walker's Mammals of the World, vol. 2. Baltimore and London: The Johns Hopkins University Press.

Savic, I., E. Nevo. 1990. The Spalacidae: evolutionary history, speciation and population biology. Pp. 129-153 in E Nevo, A Reig, eds. Evolution of Subterranean Mammals at the Organismal and Molecular Levels. New York: Wiley-Liss.

Simpson, G. 1945. The principles of classification and a classification of mammals. Bulletin of the American Museum of Natural History, 85: 1-350.

Steppan, S., R. Adkins, J. Anderson. 2004. Phylogeny and divergence-date estimates of rapid radiations in Muroid rodents based on multiple nuclear genes.

Systematic Biology

Thomas, O. 1896. On the genera of rodents: an attempt to bring up to date the current arrangement of the order. Proceedings of the Zoological Society of London: 1012-1028.

Tullberg, T. 1899. Uber das system der nagethiere: eine phylogenetische studie. Nova Acta Regiae Societatis Scientiarum Upsaliensis, 3: 1-514.