Yellow-spotted rock hyrax

Heterohyrax brucei, more commonly known as the yellow-spotted rock hyrax or bush hyrax, is a species of mammal in the family Procaviidae. It is found in Angola, Botswana, Burundi, 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.[2] Hyrax comes from the Greek word ὕραξ, or shrew-mouse.[3]

Yellow-spotted rock hyrax[1]
Conservation status
Least Concern  (IUCN 3.1)[2]
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Hyracoidea
Family:	Procaviidae
Genus:	Heterohyrax Gray, 1868
Species:	H. brucei
Binomial name
Heterohyrax brucei (Gray, 1868)
Subspecies
25, see text
Yellow-spotted rock hyrax range

Naming and classification

Heterohyrax is a bush hyrax, as opposed to a rock hyrax (Procavia capensis)[4] or a tree hyrax (Dendrohyrax).[5] 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[5] and four lower incisors that are comb-like and used to groom the fur.[6] 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.[5]

Family, Serengeti, Tanzania

Common names for the bush hyrax include yellow-spotted hyrax, bush hyrax, hogger hyrax, yellow-spotted rock hyrax, and daman de steppe (French).[2]

The genus Heterohyrax contains one extinct species, H. auricampensis, and one living, H. brucei. Within H. brucei there are 25 recognized subspecies.[5]

Heterohyrax belongs to Afrotheria, the superordinal clade of endemic African mammals that includes elephant shrews, aardvarks, golden moles, elephants and sirenians.[7]

Subspecies

(alphabetically arranged)[1]

• H. b. albipes
• H. b. antineae (no consensus if this subspecies is conspecific)[6][8]
• H. b. bakeri
• H. b. bocagei
• H. b. brucei (type species)
• H. b. chapini (no consensus if this subspecies is conspecific)[8]
• H. b. dieseneri
• H. b. frommi
• H. b. granti
• H. b. hindei
• H. b. hoogstraali
• H. b. kempi
• H. b. lademanni
• H. b. manningi
• H. b. mossambicus
• H. b. muenzneri
• H. b. princeps
• H. b. prittwitzi
• H. b. pumilus
• H. b. ruddi
• H. b. rudolfi
• H. b. somalicus
• H. b. ssongeae
• H. b. thomasi
• H. b. victorianjansae

Conservation

The Heterohyrax is on the IUCN least concern list for threatened species.[9] 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.[10] Other populations of people groups have been known to hunt the hyrax when other food sources are scarce.[8]

Population and habitat

Populations of the bush hyrax are native to Africa. Populations 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.[6]

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 one square meter of floor space and a height of 11 cm.[6] Rocky habitats are suitable living spaces because there are many crevices for the hyraxes to nest, and seek shelter from weather and predators.[11] They also live at varying elevations from sea level to 3,800 m.[5][6][8]

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 5 to 34 animals with one dominant male and 3 to 7 females and many juveniles of both sexes.[8] Other adult males tend to live on the periphery of the territory of dominant males.[7]

Studies have been conducted observing populations of bush hyraxes in the Matobo National Park, Zimbabwe. In this region populations have experienced considerable declines since 1978. Droughts in the Matobo National Park are considered as a causal factor in this decline. However, predation is also reported to be high in this region and this study reported a 52-61% mortality rate within the first year of life for the bush hyrax.[12]

The bush hyraxes, Heterohyrax brucei, are known to live with rock hyraxes, Procavia capensis[5][8] and Procavia johnstoni[7] However, different species of hyraxes do not interbreed because their sex organs vary significantly.[5][7] Some behaviors observed in populations of rock and bush hyraxes includes caring for each other's young by sharing nurseries as well as inhabiting the same rock crevices.[5] The associations observed between these hyraxes is variable and studies in Zimbabwe have shown that they often overlap habitats near parturition (the time of giving birth).[6]

Morphology

Name-giving feature

The name-giving feature of the yellow-spotted rock hyrax is a dorsal gland that is located on the lower back beneath a raised skin patch about 1.5 cm long and is surrounded by erectile hairs. However, not all Heterohyrax species have a dorsal gland.[6] 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.[5]

A bush hyrax in Hell's Gate National Park, Kenya

General features

A study conducted in Zimbabwe showed weights to range from 2.3 kg to 3.6 kg, while another study conducted in the Serengeti National Park, Tanzania found weights to be slightly lower at 1.3 kg to 2.4 kg.[4] Males and females on average do not vary in size, but sometimes the females will be slightly larger than the males.[6] 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.[5][6] Their pelts are thick and course with guard hairs measuring up to 30 mm.[6] 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 90 mm long on the snout, and 70 mm elsewhere.[5]

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.[5]

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.[6] 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.[8] 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.[6]

The bush hyraxes have an umbraculum in the pupil of their eye extending from the iris. This enables them to stare into the sun and watch for aerial predators while they sun bask.[5][6]

Rock Hyrax

The bush hyrax has a specialized kidney to compensate for the lack of water available in their natural habitat. This enables them to conserve water by producing a highly concentrated urine. The urine is so concentrated that is leaves a crystalline residue called klipstreet or hyraceum that is commonly found on the rock outcroppings where they reside.[6][13]

Reproductive

The penis of the bush hyrax is complex and distinct from that of the other hyrax genera. It has a short, thin appendage within a cup-like glans penis and measures greater than 6 cm when erect. Additionally, it has been observed that the bush hyrax also has a greater distance between the anus and preputial opening in comparison to other hyraxes. The testes are permanently intra-abdominal and vary in size depending upon season.[5]

Females have four mammae, two pectoral and two inguinal. They also have a uterus that is bicornuate, and a placenta that is chorioallantoic.[5]

Genetic variability

Genetic variation is minimal within Heterohyrax brucei. Genetic variation analysis suggests that females have a higher rate of gene transfer which may be due to greater migration success and longer migration distances of females than males. Data also show that females immigrate into colonies more frequently than males.[7]

Life cycle

The bush hyrax has been recorded to live over 10 years in the wild, with an average lifespan of 12 years.[7][12][13] Males and females reach sexually maturity between 16 and 17 months of age.[8]

Sexually mature females breed annually and breeding seasons vary based on geographic location. Peak birth rates among colonies in Kenya occur between February and March, in Zimbabwe March, and in the Serengeti, Tanzania between December and January. Breeding seasons are 7–8 months prior to when these peak birth rates have been observed based on length of gestation.[5] Females of colonies living at high elevation enter estrus as the photoperiod increases.[5] Their estrus cycle is 1–5 days.[14] For example, in the Serengeti, there is a discrete mating season of seven weeks in which females with enter estrus several times for several days each. This also synchronizes births among colonies, with all breed females giving birth within three week of each other.[8] Litter sizes vary between 1-3 young[8] but average at between 1.6 and 2.1 depending on geographic location.[5] They are born weighing 220 g to 230 g and are open-eyed, furred, able to follow adults out of the nest within several hours of birth. Young are suckled for 1–6 months before they are weaned.[5][14]

Juvenile mortality rate is high due to predation. Rock pythons, leopards, birds of prey, mongooses, and other small carnivores prey upon the bush hyrax.[8] One study conducted between 1992-95 estimated that juvenile mortality was 52.4%-61.3% per annum.[12]

Behavior

Feeding habits

The bush hyrax is a browser in regards to its eating habits.[12] They spend 80% of foraging time browsing on twigs, leaves, buds, flowers and forbs. Only rarely will they consume grass.[6] Additionally, one study reported that a colony of bush hyraxes in Zambia feeds on the leaves of bitter yams. Another study in Kenya reported that while they do not routinely feed on grasses they rely on grasses during wet seasons. Furthermore, it has been reported that in the Serengeti National Park hyraxes feed in the morning and evening, eating more in the wet season in comparison to the dry season.[8] Group feeding is common and occurs up to 50 m from the colony's shelter. However, casual feeding also occurs but at shorter distances from living space, up to 20 m, and consists of eating large amounts of food in an average of 20 minutes.[5] Bush hyraxes have also been known to climb trees in order to obtain food.[8]

Since their habitat is dry with scarce water, they obtain all the water they need from the vegetation they consume.[5]

General behavior

While they are diurnal, 95 percent of the day is spent resting, sun basking in the morning and evening, but avoiding the midday heat. While sun basking is necessary for thermoregulation, it greatly increases their risk of predation. However, they remain vigilant[5] and the dominant male will keep watch on a high rock and will give a shrill alarm if there is danger.[8] Colonies of hyraxes include on average 34 individuals, but stable polygamous family groups make up the basic social unit. Hyraxes are also highly social animals. Play behavior is generally limited to juveniles and includes fur nipping, biting, climbing, pushing, fighting, chasing, and mounting.[5]

If they are attacked or threatened, they will bite aggressively. Their keen eyesight and good hearing enables them to be aware of approaching predators or potential threats.[8]

Other documented behaviors include dust bathing to rid themselves of parasites. They also form latrines and habitually defecate and urinate in designated locations where they reside.[5]

Parasitology

The bush hyrax is likely a reservoir for Leishmania aethiopica. One study captured 48 hyraxes from various colonies from 3 different locations in Ethiopia. Of these, three were infected with Leishmania aethiopia. However, there were no visible lesions and no amastogote stage parasites present, thus indicating that the bush hyrax is a reservoir and not a suitable host. The vector of Leishmania aethiopica is Phlebotomus longipes.[15]

References

1. Shoshani, J. (2005). "Order Hyracoidea". In Wilson, D.E.; Reeder, D.M (eds.). Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Johns Hopkins University Press. p. 88. ISBN 978-0-8018-8221-0. OCLC 62265494.
2. Butynski, T.; Hoeck, H.; de Jong, Y.A. (2015). "Heterohyrax brucei". IUCN Red List of Threatened Species. 2015: e.T9997A21283287. doi:10.2305/IUCN.UK.2015-2.RLTS.T9997A21283287.en.CS1 maint: uses authors parameter (link)
3. Oxford English Dictionary.
4. Barry, R. E.; Mundy, P. J. (2002). "Seasonal variation in the degree of heterospecific association of two syntopic hyraxes (Heterohyrax brucei and Procavia capensis) exhibiting synchronous parturition". Behavioral Ecology and Sociobiology. 52 (3): 177–181. doi:10.1007/s00265-002-0509-8.
5. Barry, R. E.; Shoshani, J. (2000). "Heterohyrax brucei" (PDF). Mammalian Species. 645 (645): 1–7. doi:10.1644/0.645.1. JSTOR 3504534.
6. Kingdon, J., Happold, D., Butynski, T., Hoffmann, M., Happold, M., & Kalina, J. (2013). Mammals of Africa. A & C Black. pp. 161-165. Available at Google Books. (accessed December 12, 2013)
7. Gerlach, G.; Hoeck, H. N. (2001). "Islands on the plains: metapopulation dynamics and female biased dispersal in hyraxes (Hyracoidea) in the Serengeti National Park". Molecular Ecology. 10 (9): 2307–2317. doi:10.1046/j.0962-1083.2001.01369.x. PMID 11555272.
8. 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 at Google Books (accessed December 12, 2013)
9. 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.
10. Chiweshe, N. (2007). "Black Eagles and hyraxes — the two flagship species in the conservation of wildlife in the Matobo Hills, Zimbabwe". Ostrich: Journal of African Ornithology. 78 (2): 381–386. doi:10.2989/OSTRICH.2007.78.2.42.122.
11. Wolff, J. O., & Sherman, P. W. (2008). Rodent Societies: An Ecological and Evolutionary Perspective. University of Chicago Press. pp. 418. Available at Google Books. (accessed December 13, 2013)
12. Barry, R. E.; Mundy, P. J. (1998). "Population dynamics of two species of hyraxes in the Matobo National Park, Zimbabwe". African Journal of Ecology. 36 (3): 221–233. doi:10.1046/j.1365-2028.1998.00145.x.
13. Vaughan, T. A., Ryan, J. M., & Czaplewski, N. J. (2011). Mammalogy. Jones & Bartlett Publishers. pp. 142-144. Available at Google Books. (accessed December 12, 2013).
14. Hayssen, V. D., & Tienhoven, A. V. (1993). Asdell’s Patterns of Mammalian Reproduction: A compendium of Species-specific Data. Cornell University Press. Pp. 373-375. Available at Google Books. (accessed December 13, 2013).
15. Lemma, W.; Erenso, G.; Gadisa, E.; Balkew, M.; Gebre-Michael, T.; Hailu, A. (2009). "A zoonotic focus of cutaneous leishmaniasis in Addis Ababa, Ethiopia". Parasites & Vectors. 2 (60): 60. doi:10.1186/1756-3305-2-60. PMC 2794267. PMID 19954530.