MINIMUM AZA GUIDELINES FOR KEEPING
HYENAS AND AARDWOLVES IN CAPTIVITY


 
 

Alan Shoemaker Riverbanks Zoological Park
PO Box 1060
Columbia , SC 29202

Mike Dulaney
Cincinnati Zoo and Botanical Garden
3400 Vine St.
Cincinnati, OH 45220.


INTRODUCTION

The family Hyaenidae includes four species, three of which are heavy set, dog-like carnivores that possess similar husbandry needs. For purposes of this discussion, there are three species of hyena: the striped or common hyena, Hyaena hyaena; brown hyena, H. brunnea; and spotted hyena, Crocuta crocuta. An additional hyaenid, the aardwolf, Proteles cristatus, is represented as a mono-specific genus which, because of its unique morphology and insectivorous diet, is considered unique enough by some to be placed within its own Family, Protelidae. In view of its external similarity to the striped hyena as well as limited acceptance of this separate family (Corbet and Hill, 1991), aardwolves will also be included in this discussion.

With one exception, hyaenids are solitary carnivores that function near the top of their tropic level. While this behavior will permit the solitary species to be housed singly, it also requires that the introduction of potential mates be done carefully to prevent fighting, injury, or death.

Their aggressive nature and physical capabilities demand that owners exercise the utmost care when designing cages or exhibits for any species, regardless of size, to insure that specimens cannot escape or reach into adjacent cages, keeper or public areas. Caution also should be exercised when handling otherwise "tame" or hand-raised individuals.

                       GENERAL REQUIREMENTS

   Some aspects of captive management for both hyenas and aardwolves are similar, and are
   discussed below. Requirements unique to one or the other of the two groups are listed
   separately.

     1.Temperature: Although hyenas and aardwolves may originate from tropical climates,
        most are tolerant of a wide range of temperatures, at least during daylight hours.
        Animals kept outside should always have access to shade, especially during warmer
        parts of the year. When acclimated, most species without young require only minimal
        shelter at night, although heated shelter may be needed for animals kept in northern
        regions.

        Aardwolves may be kept outside if they have access to a nest box with heat lamps, or
        an artificial cave containing heated floor pads. In such cases, they do well when nightly
        lows reach 32 degrees F (0 degrees C) without experiencing any adverse results.
        When housed indoors, all hyaenids should be protected from temperatures exceeding
        85 degrees F (30 degrees C).

        Indoor exhibits should have 10-15 air changes per hour of non-recirculated air. A
        relative humidity of 30-70% is reasonable for this species. If kept indoors, a separate
        ventilation system or solid glass barrier separating them from visitors may be advisable
        in order to reduce the strong odor produced by their anal glands as well as to protect
        them from the threat of disease transmission.
 
 

     2.Water: Fresh clean water for drinking should be available at all times, and can be
        accomplished by using a Lixit, a sturdy portable water container firmly attached to a
        wall or an exhibit built-in, i.e. a small shallow pool or stream (spotted hyenas frolic in
        tanks 3 feet deep). Regardless of size, water containers should be cleaned and
        disinfected daily. Many hyenas enjoy bathing and shallow pools should be
        incorporated into outside exhibits, as appropriate.

     3.Sanitation: Hard-surface primary enclosures and food containers (if used) should be
        cleaned daily and disinfected with detergent and disinfectant. Logs and play objects
        should be included in this regime. Dirt substrates in outdoor exhibits should be raked
        and spot-cleaned daily. Foot baths containing appropriate disinfectants should be
        used prior to entering all hyaenid enclosures, or areas containing enclosures, and their
        use strictly adhered to by all personnel.

     4.Veterinary Care: Services of a knowledgeable veterinarian should be available prior
        to obtaining any hyaenid. Periodic (at least twice annually) fecal examinations should
        be performed to monitor and treat parasite infestation. A physical exam should be
        performed annually and the results recorded. When the opportunity arises, animals
        should be tattooed on the inner aspect of the thigh with either the studbook or
        accession (ISIS) number, or receive an transponder implant.

        The degree of susceptibility of the Hyaenidae to viruses commonly impacting canids
        and felids is not well understood, and many practices are based upon successes with
        other carnivore species. Taxonomically hyaenids are more closely related to felids
        than canids. Most carnivores should receive Fromm D canine distemper of embryo
        origin that derive from modified live virus (MLV) products. Although opinions vary,
        annual vaccinations should probably include prophylaxis against both canine
        distemper, a paramyxovirus, and feline distemper, a parvovirus (Berger et al, 1992).
        The large colony of spotted hyenas maintained at the Univ. of California-Berkeley for
        10 years are vaccinated against canine distemper, the adults on an annual basis, the
        young at 2, 3, 4 and 12 month intervals (Berger, et al, 1992). Berger et al (1992) also
        recommend protection against rabies. Only killed virus (KV) rabies products are
        recommended (Berger et al, 1992).

        Like the poorly understood nature of viral susceptibility impacting hyaenids, the use of
        modified live virus (MLV) products versus killed virus products varies among
        practitioners. Rettig and Divers (1986) prefers MLV products on viverrids for more
        reliable protection while Berger et al (1992) uses KV products to minimize the
        possibility of vaccine induced viral infection. Given the endangered status of one
        hyaenid, coupled with the increased scarcity of others from wild or captive born
        sources, KV products are probably the safer of the two approaches even if more
        frequent levels of vaccination are required. For more information, owners should
        consult Fowler (1986) and Berger et al (1992).

        Primiparous females frequently experience dystocia and should be monitored closely
        at birth (Berger et al, 1992). Impending birth may often be recognized by the pregnant
        female's refusal to eat, or by frequent urination and spotty defecation.
 
 

                       SPECIAL REQUIREMENTS

   For purposes of the following discussions, hyaenids are divided into two groups: the true
   hyenas and the aardwolf. These are based on husbandry and behavioral needs, and
   taxonomic relationship should not be inferred.

     1.HYENAS

        Hyenas are large, dog-sized carnivores well adapted to a scavenging mode of
        existence. Their massive jaws and teeth are unusually capable of cracking large leg
        bones and ribs, and smaller bones are commonly ingested whole. Adults have a head
        and body length of 41-54", a tail length of 7-10", a shoulder height of 23-37", and an
        average weight of 55-135 lb. Obesity can be a problem among female spotted hyenas
        in captivity, some overweight individuals exceeding 150 lb. Brown hyenas are the
        smallest of the three species while female spotted hyenas are 10% heavier than males.
        Also, the genitalia of female spotted hyenas mimics that of the male. The clitoris is
        large and highly erectile, and two sacks containing fibrous tissue closely resemble a
        scrotum and are located in the same area.

        Although very hardy under the simplest of husbandry regimes, hyena exhibits must be
        stout enough to withstand their destructive tendencies. Longevities exceeding 20 years
        are not uncommon. Spotted hyenas have reached 41 years of age (Jones, 1982) and
        brown hyenas 30 years (Shoemaker, 1992).

          1.Diet: Hyenas do well on felid diets that are based on beef or horse products.
             Diets of this type that already have the appropriate vitamins and minerals added
             may be obtained from commercial sources. Similar diets may also be prepared
             in-house. Whole animal carcasses (rodents, rabbits, or fowl) freshly killed or
             thawed, may be substituted upon occasion to vary the diet. Because of
             problems with obesity, hyenas may be fasted one or two days a week.

             In the past, some owners fed hyenas muscle meat from freshly butchered
             livestock. Although this source of feed is still used occasionally, practitioners
             are cautioned that diets consisting primarily of whole or ground muscle meat
             may be inadequate in vitamin/mineral content. Owners should also be wary of
             carcasses obtained from road kills or donations because of the potential for
             contamination. Feed animals from such sources should be inspected to insure
             that they are free of disease. Diets containing high percentages of fowl,
             including chicken or turkey necks, should be avoided because of inadequate
             levels of calcium and phosphorous.

             When more than one animal is maintained within the same cage, at least two
             feeding areas should be used to reduce aggression. Because hyenas are highly
             adapted to consuming bones, successful breeders recommend including several
             bones in their diet every day (Berger and Frank, 1992). Beef and sheep are
             best; where available, pig bones will suffice if frozen to prevent trichinosis. All
             bones are crushed and ingested without difficulty.

             Young can be hand raised on milk formulas that are developed for kittens. At
             Berkeley, neonates are fed 70 ml of formula four times a day, gradually
             changing to 200 ml of formula twice a day (Berger et al, 1992).

          2.Exhibit needs: Hyenas are kept in both indoor and outdoor situations.
             Normally active animals with large territories, a single specimen should have at
             least 200 square feet, and should be increased by 50% for each additional
             animal. Indoor exhibits may employ combinations of glass, gunite, solid
             masonry products, or bars for barriers, the last requiring adequate space to
             protect the public from being bitten. They may also be kept outdoors in moated
             exhibits that have a retaining wall, or behind 9 gauge chain link fencing.
             Although not good jumpers or climbers, hyenas swim well and are prodigious
             diggers, and as a special precaution, chain link fencing should extended 3 feet
             (1 meter) into the ground and extended at least 42 inches (1.2 meters)
             horizontally into the exhibit.

             Because of their nocturnal habits, particularly striped and brown hyenas, a nest
             box or cave should be provided for sleeping needs. Periodic feeding of small
             items will stimulate activity during daylight (visitor) hours, and stereotypic
             behavior can be reduced or avoided by the addition rocks, trees, and other
             impervious objects which can be periodically replaced to increase interest.

          3.Social needs: Hyenas vary widely in their social needs, and groups should be
             developed according to the behavioral characteristics of each species. Because
             female spotted hyenas are larger than males, they dominate them in competitive
             situations. Spotted hyenas are also the most social of the three species and can
             be kept in groups containing several members of both genders if specimens are
             obtained when young. A group containing 5-6 adults is probably as large as
             can be maintained without too much aggression developing, or causing ultimate
             injury to the lowest ranking individual (L. Frank, pers.comm.).

             Once a group has become stable and its members' social ranking established, it
             is not wise to remove individuals from the group unless absolutely necessary.
             Adult females are especially intolerant of other females and fighting may
             develop even after only brief separations. In order to maintain the status quo,
             medical treatment should be conservative when possible. Indeed, it is "routine"
             for subordinates to have bite wounds about their shoulders and ears but due to
             their particularly thick skin, such injuries are usually superficial.

             Striped and brown hyenas are more solitary and do best when kept in pairs.
             Although establishing pairs of striped hyenas is generally easy, the female being
             dominant over the male, establishing a pair of brown hyenas can be difficult.
             Brown hyenas have a unique social order in nature that is seldom broken in
             captivity (Mills, 1982; Owens and Owens, 1979). In nature some young males
             leave the "clan" to live solitary lives. Other males remain with their natal group.
             Those males that remain with the natal clan become non-breeders, tolerating
             periodic visits of nomadic males. Conversely, nomadic males periodically visit
             various clans to breed with estrus females. In captivity, most males assume the
             role of a clan male. If breeding does occur, reproduction usually ceases long
             before either animal is old, the male showing little interest in mating.

             Females of all species have 1 - 3 young per litter. It is common for spotted
             hyenas to rear only one young at a time, the largest cub often killing the smaller
             ones. An isolated cubbing den should be provided for females approaching
             parturition, and escape tunnels are useful when young spotted hyenas are being
             introduced to their dam's clan. Gestation is 90-110 days, the spotted hyena
             having the longest gestation.

          4.Remarks: Hand raised hyenas may become very tame toward humans. Never
             the less, they are very capable of injuring their owners and care should be
             taken before entering the cage of such animals.
 

     2.AARDWOLF

        The aardwolf is the smallest member of the Hyaenidae, having a head and body length
        of 21-31", a tail length of 8-12", and standing 17-19" at the shoulder (Novak and
        Paradiso, 1983). Adults weigh 15-22 lb. The body hair is rather long and coarse, and
        those on top of the neck and back can be erected during times of excitement or when
        the animals are startled to make the animal appear much larger than normal.
        Aardwolves are capable of making loud growls or roars which, when coupled with
        mane erection, make them appear quite formidable. Though used primarily as a means
        of marking their territory, a foul smelling odor can be ejected from anal glands in
        defensive situations.

        The aardwolf is primarily an insectivore, feeding on termites and ants. Unlike hyenas
        which have immensely powerful jaws and up to 34 teeth, the aardwolf has weak jaws
        that contain only widely spaced, vestigial cheek teeth. Only the canines of their 24
        teeth remain "normal" in size, the others appearing to be of little use. The canines are
        sharp and pointed, and are probably used for defense and in social interactions
        (Nowak and Paradiso, 1983).

        In the wild aardwolves inhabit open, sandy plains or bush country. When not in search
        of food, they spend the day in underground dens, often taking over burrows
        abandoned by aardvarks, Orycteropus afer, or crested porcupines, Hystrix
        africaeaustralis (Nowak and Paradiso, 1983). Though generally found as single
        animals or in pairs, there have been occasions where family groups of up to six
        animals have been observed. After a gestation period of 90 - 100 days, a litter of 2-3
        (range 1-5) young are born in the under-ground den site.

          1.Diet: Due to the shear numbers of insects consumed in the wild, captive
             aardwolves, like other insectivorous mammals, should be fed a palatable,
             high-protein gruel. A mixture of ground meats, dry and/or canned dog food,
             and evaporated milk, supplemented with vitamins, is used by most institutions
             maintaining this species. Because of the high caloric content of meat-based
             diets in comparison to natural ones comprised primarily of insects, captive
             aardwolves may become overweight unless the diet is monitored carefully.

          2.Exhibit Size: Being the size of a medium-sized dog, aardwolves do not need a
             large exhibit. Because of their general shyness, however, priority should be
             given to the number of hiding places included within the exhibit. For a pair of
             adults, housing should measure at least 10 feet by 10 feet as long as it contains
             1-3 nest boxes, dens, or caves, although larger enclosures may be necessary
             for some pairing because of compatibility problems.

             Aardwolves do not seem able to jump more than a few feet off the ground, and
             do not climb well. When kept outside, a shallow dry moat or low (6 feet/2
             meter) wall is usually enough to keep them contained. Aardwolves are
             prodigious diggers and this form of behavior should be considered if the
             animals are to be on natural substrate. Chain link fencing buried three feet into
             the ground and then extending three feet into the enclosure should be adequate
             to handle this situation.

          3.Social grouping: Depending on enclosure size, aardwolves can be housed
             singly, in pairs, as single sexed small groups, or as extended family groups.
             Because some pairs will not be compatible, facilities planning on breeding this
             species should be prepared to try several combinations. Unlike husbandry
             techniques commonly employed when breeding other carnivores, it is not
             always necessary to separate male aardwolves from females prior to
             parturition. Males often act as protectors of the "nursery" den. Gestation
             averages 90 - 100 days (Nowak, 1983).

          4.Remarks: Aardwolves are predominantly crepuscular or nocturnal. They can
             be kept indoors using reversed light cycles to stimulate activity during peak
             visitor hours. Facilities keeping this species in outdoor exhibits will see the bulk
             of their animal activity at dawn and dusk, with little being observed during
             midday.
 

                               LITERATURE CITED

             Berger, D.M.P.; Frank, L.G. and S.E. Glickman 1992. Unraveling ancient
             mysteries: Biology, behavior, and captive management of the spotted hyena,
             Crocuta crocuta. 1992 PROCEEDINGS JOINT MEETING
             AAZV/AAWV: 139147.

             Corbet, G.B. and J.E. Hill 1991. A WORLD LIST OF MAMMALIAN
             SPECIES, THIRD EDITION. Oxford University Press, London.

             Divers, B.J. 1986. Hyaenidae. ZOO ANIMAL MEDICINE, M. Fowler (ed.):
             827-831.

             Fowler, M. 1986. ZOO ANIMAL MEDICINE, W.B. Saunders Co., Phila.,
             PA.

             Jones, M. 1982. Longevity in captive mammals. DER ZOOLOGISCHE
             GARTEN. 52: 113-128.

             Mills, M.G.L. 1982. The mating system of the brown hyaena, Hyaena
             brunnea, in the southern Kalahari. BEHAVIORAL ECOLOGY AND
             SOCIOBIOLOGY. 10:131-136.

             Owens, D.D. and M.J. Owens 1979 Communal denning and clan associations
             in brown hyenas (Hyaena brunnea Thunberg) of the central Kalahari Desert.
             AFRICA JOURNAL OF ECOLOGY. 17:35-44.

             Nowak, R.M. and J.L. Paradiso 1983. WALKER'S MAMMALS OF THE
             WORLD. The Johns Hopkins University Press, Baltimore and London.

             Rettig, T. and B.J. Divers 1986. Viverridae. ZOO ANIMAL MEDICINE, M.
             Fowler (ed.):822-827.

             Shoemaker, A.H. 1992 1992 INTERNATIONAL BROWN HYENA
             STUDBOOK. Riverbanks Zoological Park, Columbia, SC 25 pp.
 
 
 

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