Heterohyrax Brucei

The yellow-spotted rock hyrax or bush hyrax (''Heterohyrax brucei'') is a species of mammal in the family Procaviidae. It is found in Angola, Botswana, Burundi, the Democratic Republic of the Congo, southern Egypt, Eritrea, Ethiopia, Kenya, Malawi, Mozambique, Rwanda, Somalia, northern South Africa, South Sudan, Sudan, Tanzania, Uganda, Zambia, and Zimbabwe. Its natural habitats are dry savanna and rocky areas. Hyrax comes from the Greek word , or shrew-mouse.

Naming and classification

''Heterohyrax'' is a bush hyrax, as opposed to a rock hyrax (''Procavia capensis'') or a tree hyrax (''Dendrohyrax''). Although difficult to distinguish in the field, the bush hyrax differs from the rock hyrax in being smaller and less heavily built and having a narrower muzzle.

Hyraxes have molariform teeth that are brachydont, meaning they have short crowns and well-developed roots. The bush hyrax has an upper premolar series that is the same length as the molar series, while the rock hyrax has a shorter upper premolar series and the tree hyrax has a longer upper premolar series. Hyraxes have upper tusk-like upper incisors and four lower incisors that are comb-like and used to groom the fur. While the incisors do not differentiate between the hyraxes, they do differ between sexes. Males have rigid upper incisors, while the females have rounded upper incisors. Furthermore, the male sex organs also differ greatly between these three genera of hyraxes, which may inhibit them from interbreeding.

Common names for the bush hyrax include yellow-spotted hyrax, bush hyrax, hogger hyrax, yellow-spotted rock hyrax, and (French).

The genus ''Heterohyrax'' contains one extinct species, ''H. auricampensis'', and one living, ''H. brucei''. Within ''H. brucei'' are 25 recognized subspecies.

''Heterohyrax'' belongs to Afrotheria, the superordinal clade of endemic African mammals that includes elephant shrews, aardvarks, golden moles, elephants, and sirenians.

Subspecies

(alphabetically arranged)

Conservation

The ''Heterohyrax'' is on the IUCN least concern list for threatened species.Barry, R., Bloomer, P., Hoeck, H. & Shoshani, H. (IUCN SSC Afrotheria Specialist Group) 2008. ''Heterohyrax brucei''. In: IUCN 2013
IUCN Red List of Threatened Species
Version 2013.1. It has no major threats, though it is locally hunted in some regions. Communities within the Matobo hills are reliant upon the hyraxes as a main protein source. Other people groups have been known to hunt the hyrax when other food sources are scarce.

Population and habitat

Populations of the bush hyrax are native to Africa. They have been observed to live as far north as Sudan and Eritrea and east throughout the Horn of Africa. They also live as far south as the Limpopo Province in South Africa. Additionally, isolated populations are known to be in the south-west of the Democratic Republic of Congo and Angola.Kingdon, J., Happold, D., Butynski, T., Hoffmann, M., Happold, M., & Kalina, J. (2013). ''Mammals of Africa''. A & C Black. pp. 161-165. Available a
Google Books
(accessed December 12, 2013)

Their habitats are restricted to rocky kopjes (rocky, elevated areas on a generally flat plain), sheer rock faces (krantzes), and piles of large boulders. They live in openings with at least of space and a height of . Rocky habitats are suitable living spaces because there are many crevices for the hyraxes to nest, and seek shelter from weather and predators. They also live at varying elevations from sea level to .

Studies have reported bush hyraxes to live in colonies of sometimes hundreds of animals with population densities ranging between 20 and 53 individuals per hectare. Family units are polygynous, usually five to 34 animals with one dominant male and three to seven females and many juveniles of both sexes. Other adult males tend to live on the periphery of the territory of dominant males.

In the Matobo National Park, Zimbabwe, populations have experienced considerable declines since 1978. Droughts in the park are considered as a causal factor in this decline. However, predation is also reported to be high in this region, and a 52–61% mortality rate within the first year of life was reported for the bush hyrax.

The bush hyraxes, ''H. brucei'', are known to live with rock hyraxes, ''Procavia capensis'' and ''Procavia johnstoni'' However, different species of hyraxes do not interbreed because their sex organs vary significantly. Some behaviors observed in populations of rock and bush hyraxes include caring for each other's young by sharing nurseries and inhabiting the same rock crevices. The associations observed between these hyraxes is variable and in Zimbabwe, they often overlap habitats near parturition (the time of giving birth).

Morphology

Name-giving feature

The name-giving feature of the yellow-spotted rock hyrax is a dorsal gland located on the lower back beneath a raised skin patch about long and surrounded by erectile hairs. However, not all ''Heterohyrax'' species have a dorsal gland. The secretions of the gland stain a dorsal spot of reddish-ochre to a dirty white coloration, but most commonly appears yellow. The gland is associated with sexual arousal and also plays a role in maternal recognition by young. The bush hyrax is also noted to have a white patch of hair above the eyes, where glandular tissue also occurs. Glandular tissue also occurs under the chin and in the genital area.

General features

A study conducted in Zimbabwe showed weights to range from , while another study conducted in the Serengeti National Park, Tanzania found weights to be slightly lower at . Males and females on average do not vary in size, but sometimes the females will be slightly larger than the males. They have short legs, a rudimentary tail and round ears. Their lateral and dorsal coloration tends to be grey among colonies found in arid regions and a dark reddish-brown among those found in more mesic regions. Their pelts are thick and course with guard hairs measuring up to 30 mm. Additionally they have vibrissae that provide tactile feedback located above the eyes, under the chin, along the back and sides, on the abdomen and on the fore- and hind limbs. These vibrissae, or whiskers, measure long on the snout, and elsewhere.

Other noted features include: the Jacobsen's organ which is as a specialized olfactory structure, a compartmentalized stomach into nonglandular cranial and glandular caudal sections, and a vertebral column that is convex from neck to tail.

Specialized characteristics

The bush hyrax also has specialized glands on the pads of their feet that increase their grip which helps them navigate slick rock surfaces. The pads of their feet are flat and naked while secretions from these glands keep the pads moist. The muscles in the feet contract the foot into a cup-like shape, thus resulting in a suction cup-like effect. Hyraxes are known to be excellent climbers due to this specialization and it has even been observed that if shot, they will remain perpendicular on the rock surface as if stuck to the surface.Nowak, R. M. (1999). Gray Hyraxes or Yellow-spotted Hyraxes, In: ''Walker’s Mammals of the World''. Vol. 1.JHU Press. pp. 1044-1046. Available a
Google Books
(accessed December 12, 2013) The forepaw has three well-developed digits, a rudimentary thumb, and a small fifth digit. Their digits have flat, hoof-like nails, except for the second digit, which has long, curved claw that is used for grooming. The hind paw is similar except lacking a big toe and the fifth digit is rudimentary.

The bush hyraxes have an umbraculum