Dendrohyrax arboreus

Geographic Range

Dendrohyrax arboreus is found in Africa along the southeastern coast. Its range extends southward from Kenya and Uganda to South Africa, and from eastern portions of the Democratic Republic of the Congo and Zambia in the west to the eastern coast of the continent.

• Biogeographic Regions
• ethiopian ethiopian
  • native native

Habitat

D. arboreus lives in forested areas that contain a mix of older and younger trees. The variety of forested environments it inhabits ranges from alpine, montane, highland, lowland, and riverine forests. It may be found at elevations up to 4500 m.

• Habitat Regions
• temperate temperate
• tropical tropical
• terrestrial terrestrial

• Terrestrial Biomes
• savanna or grassland savanna or grassland
• forest forest
• rainforest rainforest
• scrub forest scrub forest
• mountains mountains

• Other Habitat Features
• riparian riparian

Physical Description

D. arboreus has a somewhat marmot-like or guinea pig-like appearance. Long, soft, grey-brown fur covers the body, while the underside is paler. Hairs are lighter near their tips. The ears have a fringe of white hair. A dorsal gland is conspicuous in the middle of the back as it is ringed by creamy white hairs (total length 23-30 mm). D. arboreus lacks an obvious external tail.

These animals weigh about 2.27 kg on average, and have an average length of 520 mm. The BMR for this species is reported to be somewhat low for its size.

Four sub-species are recognized: D. arboreus stuhlmanni , D. arboreus crawshayi , D. arboreus ruwenzorii , and D. arboreus aldofi-friederici . Ranges overlap, although some habitat differentiation has been reported where the sub-species co-occur.

• Other Physical Features
• endothermic endothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Milner and Harris (1999b) reported that they were unable to determine the mating system of D. arboreus , but speculate that it may be facultative monogamy/polygyny, similar to some folivorous marsupial or primate species. Nonetheless, "it was quite apparent that their social system was very different from that of the colonial rock and bush hyrax." (Milner and Harris 1999b, p.292)

During an activity study of radio-collared animals, two male-female pairs had similar activity patterns and ranges, suggesting to the authors that either seasonal or longer-lasting bonds were indicated.

• Mating System
• monogamous monogamous
• polygynous polygynous

Breeding may occur throughout the year for D. arboreus , as evidenced by juveniles of several sizes simultaneously present in one population in Rwanda. A captive D. arboreus male-female pair produced offspring in June from a pregnancy that began before captivity and in December each year thereafter. One to two young (more often two) were born each time, and suckling began within a few hours, although the time to weaning steadily decreased from 7 months for the first litter to 3 months for the last birth.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

There is very limited information on parental investment in D. arboreus . Mothers may nurse for 3 to 7 months, and it is presumed that the young would den with their mother during this time. Individuals with deciduous teeth remaining, presumably juveniles, were observed to be solitary during a radio-collar study. However, one group, consisting of an adult, two sub-adults, and a juvenile were repeatedly found in each other's company also. This may indicate some parental investment once the young leave the den.

One account reported that offspring may eat solid food beginning their second or third day.

• Parental Investment
• no parental involvement
• precocial precocial
• female parental care female parental care
• pre-fertilization
  • protecting
    • female
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-weaning/fledging
  • provisioning
    • female
  • protecting
    • female
• pre-independence
• post-independence association with parents

Lifespan/Longevity

Hoeck reports the longevity for the genus Dendrohyrax as "10 years plus." A captive female, pregnant when brought into captivity, lived at least four additional years, though her lifespan after the study ended is not reported.

Behavior

Although some report that southern tree hyraxes sometimes occupy rocks in Tanzania and Uganda, published studies are from South Africa and Rwanda where these animals reside in the trees. Their behavior in this habitat is more widely reported, and the following applies to these populations.

D. arboreus is arboreal. It lives in dens created in trees, either in a cavity or hollow of a decaying tree or a nook between branches. It feeds primarily in the trees. Most of its time is spent in isolation. It has an unusual activity pattern, being slightly more active for a short time in the evening, and then once more at a different time (although when this second period occurs differs between sexes). It is commonly known for its vocalizations, which may be loud and erie-sounding (see Communication section). D. arboreus accumulates excrement at the bases of the trees it inhabits, therefore dens (or prior den trees) are readily located.

D. arboreus is relatively inactive. It it active only about 16% of the day (i.e. feeding, traveling, fighting, or vocalizing). It exhibits a somewhat bimodal pattern of activity, but males and females have different activity peaks. All D. arboreus have a peak of activity within 3 hours of sunset, females are also active during midday, whereas males have a separate activity peak in the pre-dawn hours. These times are when it is most likely to feed.

It has been suggested that human influence may cause their activity patterns to shift. Captive D. arboreus were found to be most active at dawn and dusk.

• Key Behaviors
• arboreal arboreal
• nocturnal nocturnal
• crepuscular crepuscular
• motile motile
• sedentary sedentary
• solitary solitary

Home Range

Home range size of D. arboreus may increase with age. In a study in Rwanda, total home ranges varied from 600 to 2,800 square meters, while core areas (where every tree is used at least 1% of the time) varied from 150 to 2,500 square meters.

Patches of forested areas most commonly occupied are at least 5 ha in size.

D. arboreus is sensitive to changes in the forests that it occupies: moderate amounts of wood removal may provide better habitat, but too great a removal of wood reduces the probability that a particular area is habitable. Additionally, nearby forest or brush fires reduce the liklihood of inhabitance by D. arboreus .

Communication and Perception

D. arboreus has a prominent scent-gland, which may be used in marking territory or communicating. The large "latrines" under their den trees clearly demarcate use of a home range.

Throughout their range, southern tree hyraxes are particularly well known for their nighttime screaming. During the dry season, males will call in the early morning hours (between 2 an 4 AM). There appears to be a social communicative function to these calls. "Each animal builds up to a strained crescendo of screams and a calling animal appears to initiate responses from its neighbours so that on a suitable night there may be concert periods of croaking screams ringing out through the forest." (Kingdon 1971, p.328)

A clear interpretation of this behavior has not been made: there was no correlation between frequency, intensity, duration, initiation time of calls, or environmental variables. Breeding activities were not investigated in tandem with calling behavior. One interpretation is that calling follows intense feeding periods but is linked to territoriality and sexual function.

Some tactile communication undoubtedly occurs between mothers and their young, as well as between mates. Although these animals can see, it is not known whether they use any visual signals in their communication.

• Communication Channels
• tactile tactile
• acoustic acoustic
• chemical chemical

• Other Communication Modes
• choruses choruses
• scent marks scent marks

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

D. arboreus is generally folivorous. However, other plant parts constitute a large proportion of its diet. It is a selective browser, eating a combination of foods to maintain a delicate energy balance, not necessarily in proportion to the item’s abundance. Nearly 150 individual plant species were identified from fecal remains of D. arboreus in South Africa. The most commonly eaten species may constitute a low of 38% of the total diet, and two dozen species may only constitute 75% of all material eaten.

Different parts of plants are consumed by D. arboreus . These include leaves, petioles (discarding the leaf), twigs, shoots, fleshy fruit, and hard seeds. Individual species are too many to list, but Hagenia abyssinica , Hypericum revolutum , Ficus spp., and Podocarpus falcatus are common.

• Primary Diet
• herbivore herbivore
  • folivore folivore

• Plant Foods
• leaves
• wood, bark, or stems
• seeds, grains, and nuts
• fruit

Predation

Verreaux eagles subsist almost entirely on hyraxes. Additionally, Martial and Tawny eagles, leopards, lions, jackals, spotted hyenas, and snakes prey upon hyraxes. In Rwanda, the most common predators are feral dogs. It has been speculated that the exceptionally limited amount of time D. arboreus spends on the ground at night may be a predator avoidance strategy to avoid the dogs. Humans are also known to eat D. arboreus .

Ecosystem Roles

Southern tree hyraxes disperse the seeds of fruits they eat. Their waste products contain high amounts of calcium carbonate, which eventually form "outcroppings" and may play a role in localized nutrient cycling. As hyraxes generally are the major prey of Verreaux eagles, D. arboreus may have a significant impact on this species. Finally, as cavity-dwellers, they may provide structural components of forests.

• Ecosystem Impact
• disperses seeds
• creates habitat

Economic Importance for Humans: Positive

D. arboreus has economic importance to humans in a number of different ways. The crystallized excrement of this species has been used by both Europeans and South African tribes as a medicinal to treat epilepsy, hysteria, St. Vitus's dance, and general injuries. It has also been used as a vitamin supplement. Humans hunt Dendrohyrax spp. for food, and it is said that their large liver is a delicacy. Finally, the fur of this species may have some value, as the pelts of other members of the genus, such as D. validus , are used near Mt. Kilimanjaro. The fur of tree hyraxes is generally quite soft.

• Positive Impacts
• food food
• body parts are source of valuable material
• source of medicine or drug source of medicine or drug
• produces fertilizer

Economic Importance for Humans: Negative

It is possible that D. arboreus may be a minor nuisance to agriculturalists. There is also some chance that this species is part of the life cycle of parasites capable of infecting humans. A species of Dendrohyrax located in Kenya and Ethiopia harbors the leishmaniasis-causing parasites.

• Negative Impacts
• injures humans
  • carries human disease
• crop pest

Conservation Status

The IUCN lists D. arboreus in South Africa as VU B1+2 status as of 1996, meaning it is vulnerable ("a high risk of extinction in the wild in the medium-term future"), due habitat fragmentation and continued population decline. In fact, there have been recent studies documenting the habitat needs of D. arboreus in an effort to curb its decline.

Other Comments

Dendrohyrax arboreus crawshayi and D. dorsalis have reportedly interbred in Kenya, producing a distinct hybrid: Dendrohyrax dorsalis marmota .

Additional Links

Encyclopedia of Life

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Anna Williams (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor.

References

Gaylard, A., G. Kerley. 2001. Habitat assessment for a rare, arboreal forest mammal, the tree hyrax Dendrohyrax arboreus . African Journal of Ecology , 39: 205-212.

Gaylard, A., G. Kerley. 1997. Diet of tree hyraxes Dendrohyrax arboreus (Hyracoidea: Procaviidae) in the Eastern Cape, South Africa. Journal of Mammalogy , 78/1: 213-221.

Hoeck, H. 2001. Hyraxes. Pp. 448-451 in The New Encyclopedia of Mammals . Oxford, UK: Oxford University Press.

Jones, C. 1984. Tubulidentates, Proboscideans, and Hyracoideans. Pp. 523-535 in Orders and Families of Recent Mammals of the World . New York, NY: John Wiley & Sons, Inc..

Kingdon, J. 1971. East African Mammals: An Atlas of Evolution in Africa, Volume I . London: Academic Press Inc..

Lawes, M., P. Mealin, S. Piper. 2000. Patch occupancy and potential metapopulation dynamics of three forest mammals in fragmented afromontane forest in South Africa. Conservation Biology , 14/4: 1088-1098.

Milner, J., S. Harris. 1999a. Activity patterns and feeding behaviour of the tree hyrax, Dendrohyrax arboreus , in the Parc National des Volcans, Rwanda. African Journal of Ecology , 37: 267-280.

Milner, J., S. Harris. 1999b. Habitat use and ranging behaviour of tree hyrax, Dendrohyrax arboreus , in the Virunga Volcanoes, Rwanda. African Journal of Ecology , 37: 281-294.

Rudnai, J. 1984b. Activity cycle and space utilization in captive Dendrohyrax arboreus . South African Journal of Zoology , 19/2: 124-128.

Rudnai, J. 1984a. Suckling behaviour in captive Dendrohyrax arboreus (Mammalia: Hyracoidea). South African Journal of Zoology , 19/2: 121-123.

Smithers, R. 1966. The Mammals of Rhodesia, Zambia and Malawi . London: Collins Clear-Type Press.