Rock hyraxes in Kenya, © 2007 Daniele Colombo
The order Hyracoidea (hyraxes) is comprised of small to mid-sized herbivores, with small tails, short legs, and small round ears (Grzimek, 2004). The name comes from Greek and Dutch meaning “shrewmouse” and “rockbadger” which is a misleading name since they are not part of the rodent family (Grzimek, 2004). They can be found in parts of Africa and the Middle East, in forested areas and vegetation zones on rock boulders. There are 5 to 11 species living today, however this number is variable since genetic research is ongoing with this group (Grzimek, 2004).
Hyraxes tend to be small to medium sized herbivores, which means they are approximately 44–54 cm in length, and have a mass between 1.8–5.4 kg (Grzimek, 2004). The males and females tend to be similar in size, however the size of individuals in a population varies with environmental factors. The size of an individual has shown a high correlation to the amount of precipitation in the area (Klein and Cruz-Uribe, 1996). Hyraxes differ in colour based on species and on the environments that they are found in. They can range from a light gray to a dark brown. Hyraxes have bulging eyes, a small tail, and a skunk-like muzzle (Grzimek, 2004).
The hyraxes' feet are equipped with rubbery pads, which allows them to climb trees very quickly and jump great distances. Hyraxes have a unique ability to sweat from their feet, and this (along with other sweat glands) allows them to maintain a constant body temperature between 35-37°C when the air temperature rises above 25°C (Grzimek, 2004). Due to this method of cooling, a low metabolic rate, and a very low urine volume hyraxes do not need to consume large amounts of water (Bartholomew, and Rainy, 1994). They also have an interesting digestive system, in which the stomach is comprised of three sections, and symbiotic bacteria aid in the digestion of their food (Grzimek, 2004).
Scientists initially thought hyraxes were rodents, closely related to guinea pigs (Grzimek, 2004). This error lead to the name of the group, Hyracoidea (shrewmouse). Later insight into morphology and the discovery of a 40 million year old fossil bed uncovered evidence for the relationship between hyraxes and elephants and seacows (Grzimek, 2004). Even the sizes of hyraxes found in the fossil records were more similar to those of paenungulates (elephants and seacows). The hyraxes are now part of the paenungulates, which is part of the subgroup Afrotheria (Grzimek, 2004). This relationship is also supported by mitochondrial DNA evidence (Yang et al. 2003).
The fossil record indicates that hyraxes have been an important part of ecosystems in Africa as a grazer for 40 million years (Grzimek, 2004). The group has retained several primitive features such as use of molars instead of incisors to chew food, imperfect endothermy, and their short legs (Grzimek, 2004).
Habitat and Distribution
Hyraxes are endemic to Africa, except for some areas in the Middle East (Sinai, Lebanon and Saudi Arabia), in areas with large rock outcrops. These rock outcrops allow for a suitable temperature (17-25°C) and a low humidity for hyraxes to survive in (Grzimek, 2004). These rock outcrop microhabitats need to provide specific features in order to support hyraxes. Some abiotic factors include protection from fire and rainfall, and they must have holes for them to hide in. The biotic factors that affect habitat selection are protection from predators, availability of food and little to no competition (Grzimek, 2004). Depending of the species of hyrax, they can be in deserts or areas with moderate rainfall and from sea level to alpine areas (Grzimek, 2004).
The behaviour and ecology of hyraxes is very species specific and can range for a diurnal and gregarious species to nocturnal and solitary species (Grzimek, 2004). However there are some patterns in behaviour which all hyraxes display. Some of these patterns for example are grouping together to share body warmth and interacting/living with other hyrax species (Grzimek, 2004). Other behaviours which hyrax species share are listed below.
Hyraxes tend to eat mostly leaves, twigs, fruit, bark and grass. They are able to eat the bark and twigs because of the design of their gut and their relationships with symbiotic bacteria, which allows them to digest tough fibers (Rubsamen, Hume and Engelhardt, 1981). They also have the ability to survive on very little water due to highly efficient kidneys (Grzimek, 2004). When feeding the hyraxes are the furthest away from their shelter, this causes the main or head male hyrax to stand guard watch over the rest of the group when they feed. If he sees a predator, he will make a sound to signal the rest of the group to hide (Grzimek, 2004). Feeding generally takes place in the morning (7:30 am) and the afternoon (6 pm) and lasts no longer than 35 minutes (Grzimek, 2004).
Most hyrax populations have a polygamous mating structure; i. e., one male hyrax mates with females. This male is referred to as the territorial (head) male, and he is responsible for watching over the group when they feed (Grzimek, 2004). There are 17 females and juveniles to one territorial male. The juveniles are equally male to female, and once reaching adulthood (30 months of age) they disperse at least 2 km away from their mothers (Grzimek, 2004). As for mating in communities with multiple species living together, the species do not interbreed since they do not have the same mating behaviour and have different reproductive anatomies (Grzimek, 2004). In most species the male signals for mating to begin. Once a female becomes pregnant the gestation period is 26-30 weeks and she can give birth to one to four young at one time (Grzimek, 2004).
Relationship with Humans and Consevration Status
Hyrax populations are sensitive to habitat degradation and fragmentation caused by human activities. These factors have caused some hyrax species to be categorized as vulnerable by IUCN (Grzimek, 2004). Humans have very little use for the hyrax, other than for its fur, and native populations use it in traditional medicines (Grzimek, 2004).