Hyrocoidea (Hyraxes)


Chapter 54

Hyrocoidea (Hyraxes)



Julie E. Napier



Biology


The hyrax is a unique animal and the only one in the order Hyrocoidea. The one recognized family, Procaviidae, consists of three species: (1) the cape or rock hyrax (Provacia capensis), (2) the gray or yellow-spotted hyrax (Heterohyrax sp.), and (3) the tree or bush hyrax (Dendrohyrax sp.) (Table 54-1). Although the hyrax looks more like a rodent or a rabbit, its closest living relatives are the elephant, as well as the manatee and dugong, both of which are marine mammals. Hyraxes may be found throughout southwest Asia and most of Africa.22 The rock hyrax is the most widely held species in zoologic institutions.




Unique Anatomy


Hyraxes are stout, squat animals with short legs (Figure 54-1). They have a double coat, with a finer under layer and coarser outer layer, and a scent gland on the back covered in longer hairs (see Table 54-1). They have a cleft upper lip, short round ears, and guard hairs around the snout. The deciduous dental formula for the hyrax is: incisors (I) 2/2, canines (C) 1/1, premolars (P) 4/4, for a total of 28 teeth. The permanent dental formula is: I 1/2, C 1/1, P 4/4, molars (M) 3/3 for a total of 38 teeth. Hyrax teeth, which are adapted for eating grasses, have high crowns and relatively short roots. The two upper incisors, used for grooming, are elongated and tusklike in appearance and are often mistaken for canines.



These animals are plantigrade, with four digits on the front feet that look like hooves and three digits on the hindfeet. The second digit on the hindfoot has a long claw, also used for grooming. The other two digits are hooflike in appearance as well. The soles of the feet are rubbery in texture, which gives these animals traction on smooth, uneven, or steep surfaces. The only location of sweat glands in this species is the plantar surface of the feet.4


The hyrax’s digestive system is adapted to handle relatively low-quality food. A simple stomach has glandular and nonglandular sections, a tubular small intestine, and a large intestine that is almost as long as the small intestine. The large intestine is unique to this species. It starts with a cecumlike sac, which has a narrow connecting colon with thick walls and a second connecting colon with wide, thin walls. The second portion of the colon is where the primary absorption of water and volatile fatty acids takes place. The two connecting colons are followed by a colonic sac with two appendages that ends with a distal colon. The hindgut is important for microbial digestion.1,10,17 The hyrax does not have a gallbladder. The testicles of the male are intraabdominal and are attached to the posterior pole of the kidney. Females have four mammae and a duplex uterus.


The eye of the hyrax is unique, as a portion of the iris above the pupil bulges slightly into the aqueous humor to cut off light directly above the animal.17



Special Housing Requirements


The hyrax is a poor thermoregulator, and its body temperature fluctuates in relation to the environment, so it is important to provide a shelter with relatively stable environmental temperatures and humidity. Hyraxes spend many hours basking in the sun and will often huddle in groups when temperatures start to drop. These animals are reluctant to emerge if the weather is cold or rainy, but they may also seek shelter in extreme heat from the sun. They should have a heated area or shelter provided if they are exhibited outdoors.


In spite of their build, hyraxes are quick, agile, and adept at climbing. A variety of surfaces should be provided for this activity. They are also capable of jumping up to 1.5 meters (m) so enclosures should be designed accordingly. These animals are quite fastidious and prefer to use a designated area for urinating and defecating, so their exhibit should contain a sandy area for these purposes so that it may be cleaned daily.



Feeding


In the wild, the hyrax is a facultative grazer, feeding on anything from succulents to lower-quality fibrous foods. They spend less than an hour a day eating. The relatively long transit time for digestion, coupled with a low nitrogen requirement, enables this animal to survive periods of poor diet and low protein availability.


The hyrax has an effective calcium absorption mechanism in the alimentary canal. The majority of excess calcium is excreted in urine, as in the rabbit, guinea pig, and other rodents. This may give the hyrax urine a chalky appearance. Hemosiderosis has been a concern in the hyrax, so low-iron diets are recommended.3,6 A 2004 study found that hyraxes fed a low-fiber diet were more likely to be affected by pancreatic islet fibrosis (PIF).8


Most zoologic institutions feed hyraxes once a day and offer either some type of pelleted herbivore feed or primate biscuits with a variety of vegetables and greens, a small amount of fruit and some type of hay ad libitum.17 Water is consumed, when available, but is not generally needed. The hyrax efficiently metabolizes water by producing highly concentrated urine, having low evaporative water loss because of the low metabolic rate, and minimal fecal water loss. Consequently, water demand may usually be met in the diet. This species is not known to exhibit copraphagy as adults, but juveniles will eat or may be fed feces to stimulate the appropriate bacteria for a diet high in fiber.17



Handling and Restraint


Some animals, especially those that have been hand raised, will adjust to handling by humans. However, most hyraxes are caught by using a strong hoop net and heavy leather gloves. Care must be taken to avoid causing injury and stress to the animals. Hyraxes may also be run into a crate or trained to go into one.



Anesthesia and Surgery


Inhalant anesthesia, specifically isoflurane, is the most common form of anesthesia used in this species. After manual restraint by running the animal from a crate into an induction chamber or by placing a plastic bag over the crate itself, the anesthetic is most often administered via a face mask. It may be challenging to intubate the hyrax, but if intubation is elected, a 4- or 5-millimeter (mm) endotracheal tube may be used.12 Injectable anesthetics may also be used (Table 54-2). The most common reasons for anesthesia are surgery or treatment for trauma, caused either by conspecifics or falls, and for dental disease.



TABLE 54-2


Chemical Restraint Agents Used for the Hyrax*





























































































Generic Name Trade Name and (Source) Dosage Reversal Agent, (Trade Name and Source) Dosage
INDIVIDUAL AGENTS
Acepromazine
Diazepam		 PromAce (Boehringer Ingelheim Vetmedica, Inc.),
AceproJect (Butler Schein)
Valium (Roche)		 0.5–1.0
milligram per kilogram (mg/kg), intramuscularly (IM)
1–5 mg/kg, IM		 None
Flumazenil (Romazicon, Roche)		 0.0.1–0.2 mg/kg
slow IV to effect
Isoflurane IsoFlo (Abbott)
Aerrane (Anaquest)
Isovet (Schering/Plough)		 3%–5%
induction;
1%–2%
Maintenance		 None
Ketamine Ketaset, Vetalar (Fort Dodge) 20–50 mg/kg, IM None
Medetomidine Domitor (Pfizer) 0.25 mg/kg, IM Atipamezole (Antisedan, Pfizer) 5× mg total of medetomidine, IM
Midazolam Versed (Roche) 1–2 mg/kg, IM Flumazenil (Romazicon) 0.01–0.2 mg/kg
slow IV to effect
Propofol Diprivan (Zeneca Pharmaceuticals) 7.5–15.0 mg/kg, intravenously (IV) (slow bolus over 5 minutes) None
Sevoflurane SevoFlo (Abbott Animal Health)
Ultane (Abbott)		 3%–8%
induction;
1%–4%
Maintenance		 None
Tiletamine–zolazepam Telazol (Fort Dodge) 5–25 mg/kg, IM Flumazenil for zolazepam, (Romazicon) 0.01–0.2 mg/kg,
slow IV to effect
Xylazine Rompun (Bayer) 1–5 mg/kg, IM Yohimbine (Antagonil, ZooPharm, Yobine, Lloyd) 0.2–1.0 mg/kg, IM or IV
COMBINATION AGENTS
Ketamine–diazepam, followed by isoflurane Ketoset or Vetalar–Valium 5–30 mg/kg
and 1–3 mg/kg, IM		 None
Flumazenil (Romazicon)		 0.01–0.2 mg/kg, slow IV to effect
Ketamine–xylazine Vetalar–Rompun 30–40 mg/kg
and 3–5 mg/kg, IM		 None
Yohimbine (Antagonil, Yobine)		 0.2–1.0 mg/kg, IM or IV
Ketamine–acepromazine Ketoset or Vetalar–PromAce 40 mg/kg and
0.5–1.0 mg/kg, IM		 None
None
Ketamine–medetomidine Ketaset or Vetalar–Domitor 5 mg/kg and
0.35 mg/kg, IM		 None
Atipamezole (Antisedan)		 5× mg total of medetomidine


image



* Use lower end of dose range for debilitated, geriatric, or obese animals for optimal results.



Diagnostics


Venous access sites for this species include the jugular and the femoral veins. Boxes 54-1 and 54-2 list the hematologic and serum chemistry reference ranges, respectively, for the rock hyrax. Annual examinations may include, but are not limited to, blood work; a dental examination and tooth trims, as needed; routine fecal checks for parasites; fecal or rectal culture; nail trims, as needed; and radiography. Vaccinations are given to this species for rabies and tetanus. The necropsy database for hyraxes includes four cases of tetanus as probable cause of death.17


Tags:
Aug 27, 2016 | Posted by in EXOTIC, WILD, ZOO | Comments Off on Hyrocoidea (Hyraxes)

Full access? Get Clinical Tree
Get Clinical Tree app for offline access