Giant root-rat

The giant root-rat (Tachyoryctes macrocephalus), also known as the Ethiopian African mole rat or giant mole rat, is a rodent species in the family Spalacidae.^[2] It is endemic to Ethiopia's Bale Mountains. Its natural habitat is subtropical or tropical high-altitude grassland, where it can reach densities of up to 2,600 individuals per square kilometre. It is threatened by habitat loss.^[1]

Giant root-rat
Bale Mountains, Ethiopia
Conservation status
Endangered  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Rodentia
Family:	Spalacidae
Genus:	Tachyoryctes
Species:	T. macrocephalus
Binomial name
Tachyoryctes macrocephalus Rüppell, 1842
Synonyms
Tachyoryctes hecki Neumann & Rümmler 1928

Phylogeny

Tachyoryctes macrocephalus is a species endemic to grasslands in Ethiopia's Bale Mountains.^[3] It is a member of the genus Tachyoryctes, and a sister clade to the genus Rhizomys.^[4] Fossil records have suggested the species previously lived in South Asia up to northern India.^[5]

Characteristics

Tachyoryctes macrocephalus are typically have small eyes and thick russet fur.^[6] They have large upper teeth called incisors that are especially prominent.^[6] The eyes are placed near the top of the forehead, and are sometimes called "periscopes" due to their ability to scan for predators.^[7] Individuals usually lack a part of the ear called a pinna.^[8] The limbs are typically short with claws, and individuals have short tails.^[9] Their weight can range between 160 grams to 930 grams. The length of their body ranges from 160 millimeters to 313 millimeters.^[10] Their molars are hypsodont (having a high crown and a short root), and the interparietal bone is very short.^[10]

The hair is usually gray at its base, and the head is significantly larger than the rest of the body.^[11] The rodents typically eats grasses nearby their burrows and spend the majority of their time underground. The typical body mass is around 1 kilogram.^[12] In the skeleton, the occipital shield is small and horizontal, the zygomatic plate is very broad and vertical, the mesopterygoid fossa is V-shaped and the back of the glenoid fossa is open.^[5]

Reproduction

Tachyoryctes macrocephalus breeds year-round and gestation lasts for 37 to 49 days.^[10] Some females are polyestrous (conceiving a second young whilst nursing the first) or breed once every 6 months.^[10] Males sometimes deposit a copulatory plug to help assist during mating.^[13] Individuals use rainfall and changing temperatures to help determine the appropriate time for breeding.^[14] Females in the genus Tachyoryctes are considered induced ovulators, where ovulation usually only occurs during mating.^[15]

Foraging

While the other mole rats not only live but also feed underground, this species mostly forages above ground, by digging a new tunnel to a patch of herbage. It forages for about 20 minutes, until it has exhausted the supply of herbs about its tunnel, after which it blocks the tunnel it has built from the inside. It mostly eats grasses and herbs, with some individuals feeding mostly on roots.^[9] It retains its specializations for digging tunnels because of the constant threat of predators, especially the Ethiopian wolf, which is specialized to a diet of mole rats. Ethiopian wolves catch mole rats by ambushing them after they have constructed a new foraging tunnel, chasing them into their tunnel, and then vigilantly waiting for them to resurface.