Rhino Husbandry Manual
Greater One Horned Rhinoceros
Outdoor Enclosures
​Design
In designing facilities to maximize rhino health and reproductive success, it is important that the environment contain as many salient features as possible found in the natural environment (for more detailed information on the natural habitats of the various rhino species, see the Behavior chapter). The species to be exhibited will dictate the design of rhino facilities, as species differ in their group compositions and enclosure requirements. Additionally, whether an institution wishes to maintain rhinos only for exhibit or for breeding will determine the design of rhino enclosures. Whenever possible, institutions are encouraged to plan for breeding capabilities, but the various SSP coordinators and TAG chairs recognize the need for display-only exhibits which can facilitate education and/or research. These exhibits serve rhino management programs by holding non-reproductive and single-sex specimens. The following section outlines design considerations for indoor and outdoor rhino facilities, as well as aspects of chute design for rhino restraint.
Enclosures
The design of zoo enclosures for rhinos requires an understanding of rhino biology, behavior and social organization. As previously stated, black, white and greater one-horned rhinos vary in their levels of sociality and thus have different housing requirements. The design of rhino enclosures also depends on the type of rhino program (exhibit only or breeding) and the number of animals. In all cases, the larger and more varied the enclosure, the better. Tables 4.11 and 4.12 list the recommended animal numbers for institutions holding rhinos (see Management chapter) and the enclosure types recommended depending on institutional goals. It is important to note that for the most part, exhibit and holding-space availability will dictate an institution’s designation as either a breeding or an exhibit facility. Design elements for a breeding facility should include an outdoor primary enclosure (with separation capabilities), indoor holding and an isolation area. Additionally, breeding institutions must have space for any offspring to be held for up to three years of age. Exhibit-only facilities should have an outdoor primary enclosure and indoor holding areas (both with separation capabilities). It will be recommended that exhibit-only facilities receive pre-or post-reproductive-age or single-sex groups of animals.
In general, it is recommended that enclosures be designed such that animals may be kept outdoors as much as is possible within the following temperature constraints. Rhinos should not be locked outside when the temperature is below 4.4°C (40°F); sun, wind chill and rain should be considered in calculating temperature. During extremely cold weather, rhinos should not have access to pools or mud wallows; pools should be drained and mud wallows filled with substrate. Animals should not be let out if enclosures are icy. Temporary exposure to temperatures below 4.4°C (40°F) for cleaning is left to the discretion of management. Localities that experience average daily temperatures below 10°C (50°F; average of high and low temperatures over a 24-hr period) should provide heated facilities capable of maintaining a minimum temperature of 13°C (55°F).
Table 4.11 Recommended numbers of animals for institutional holding.
Rhino Species
Recommended Min. Group
For Breeding
Preferred Optimal Holding for a Breeding Institution
Exhibit Only (For exhibition only)
White
Black
1.2
2.4 (one herd and one back up male)
1.1 or 0.2* Adam can you confirm?
2.2 (2 pairs)
1.1 or 0.2
1.1
Greater one horned
1.1***
2.2 (2 pairs)
1.1 or 0.2**
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*Must be able to hold for up to three years following birth.
**Multi-male bachelor groups have been maintained in very large enclosures.
*** In the case of greater one-horned rhinos, males and females should be introduced only during the female’s estrous period. Institutions with very large enclosures may be able to hold opposite-sex animals together consistently.
Table 4.12. Recommended enclosure types and sizes for zoo-housed GOH rhinos [in sq m and (sq ft)].
Individual Holding (per rhino) Exhibit Only (per rhino) Breeding/Communal
Indoor Outdoor Indoor Outdoor Indoor Outdoor
30 sq. m 186 sq. m 215 sq. m 929 sq. m Not 2,787 sq. m
(320 sq ft) (2,000 sq. ft) (2,320 sq. ft) (10,000 sq. ft) Recommended (30,000 sq. ft)
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Outdoor Housing
Several general outdoor enclosure designs are recommended that incorporate the data available on the behavior and ecology of wild black, white, and greater one-horned rhinos. As previously described, rhinos of all species may be less solitary than was originally thought. Given very large yards or ranch situations, even opposite-sex greater one-horned rhinos (considered the least social of the commonly held rhino species) may be housed together. For the most part, however, rhinos are somewhat territorial; therefore, more than one outdoor yard is strongly recommended. To provide a large area for introductions of greater one-horned rhinos, a communal yard adjacent to individual yards should be available. If the space is not available, two adjacent yards may be opened for male/female introductions. In many respects, the critical enclosure characteristic is the availability of escape routes and visual barriers, which serve to hide or prevent access to a pursued animal. Gates may be used as escape routes, provided that care is taken to prevent dead-end corners and to create “run-arounds” (brush piles, earth, or boulders) so that an animal can enter or leave the yard without an aggressor blocking or guarding the only exit. Enclosure size depends on whether rhinos are kept for exhibit-only or breeding purposes (Table 4.12). It should be noted that a calf is considered an adult with respect to minimum space requirements after weaning; this should be considered in determining minimum enclosure size.
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Primary Barriers
The barrier between rhinos and the viewing public is a critical element in the design of the outdoor exhibit. This primary barrier should allow visitors a clear view of the animals from a safe location. Many types of primary barriers are available, the most common of which are walls, fencing, dry moats and water moats. One consideration in choosing fence type should be the size of the enclosure. For example, smaller exhibits should be constructed with barriers that provide as much visual exposure as possible. Moats, both dry and water, are less desirable for breeding groups because of the potential for accidents.
Fencing
Because any of the rhino species may climb, a primary barrier should be a minimum of 1.5 m (5 ft) high and non-climbable. In small enclosures, particular attention should be given to the climbing ability of rhinos and to the need for separating aggressive animals. A secondary barrier or a taller primary barrier may serve to counter these problems. It is important to consider fence spacing and keeper access/exit in the event of an emergency as well. Recommended materials for primary fencing include solid concrete or rock walls, horizontal pipe or cable spaced 25 to 30 cm (10-12 in) apart and vertical pipe or posts spaced 25 to 30 cm (10-12 in) apart. Cable should be used only for horizontal fences. The size of the exhibit to be fenced will determine the strength and type of fencing material used, as each type has both advantages and disadvantages. Concrete surfaces and bare steel cable create surfaces that may encourage rhinos to horn-rub excessively, causing abnormal horn wear. If necessary, surfaces should be covered with a non-abrasive material; one solution is to insert steel cable through plastic pipe, or concrete surfaces can be covered with non-toxic wood. If poles are used, each should be approximately 30 cm (12 in) in diameter and set in concrete with approximately 1.8 m (6 ft) underground. Poles should be spaced as closely together as possible to prevent rhinos from getting their horns through and uprooting the fence. Creosote-treated poles, which are dangerous to rhinos, should not be used. Rocks or a rock apron can be utilized to protect the poles or other objects in the exhibit from damage. A rock apron should extend 1.8 m (6 ft) from the leading edge of the object to offer adequate protection. If small rocks are used, they should be several layers thick; otherwise, a single layer of very large rocks is probably adequate.
Dry Moat
The use of a dry moat requires one vertical wall, which should be a minimum of 1.5 m (5 ft) high, located on the public side. The second wall should be sloped at a maximum of 30° so that the animals can climb out. This gradual decline of the exhibit substrate down to a solid wall can be used to create a moat effect, but ditch moats with two vertical walls are considered dangerous to rhinos and are not recommended. The floor space in the moat should be a minimum of 1.5 m (5 ft) across to prevent rhinos from being trapped, and surface substrate for the moat should provide stable footing (recommended materials include dirt, gravel, sand, etc.).
Water Moat
Water can be utilized as a primary barrier, although it carries the risk of drowning or injury, especially for calves. Dimensions and specifications for a water moat should be the same as those listed above for a dry moat. Pools may also serve as primary barriers, provided the walls are high enough [at least 1.5 m (5 ft) high] to prevent animals from climbing out. Once a rhino has its chin over the top of a wall, it can get its front feet over as well
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Secondary Barriers
Though not critical to the design of outdoor enclosures, secondary barriers may protect exhibit features or lessen stress on primary barriers. Recommended types are butt rails, vertical poles and electrically charged, or “hot,” wire. Plantings can also serve as a secondary barrier when used to create a visual screen. For example, plantings that extend above a low wall can give the appearance of a bigger wall [although the primary barrier height minimum of 1.5 m (5 ft) still applies]. Electric fencing can be used to deter animals from destroying plantings, trees and other secondary barriers. Rock aprons may also be used around trees and fence lines as secondary barriers.
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Gates
Enclosure gates can be the weakest points of the exhibit, therefore adequate hinge and lock strengths are very important. Interior doors are usually constructed of heavy-gauge steel or pipe that is hinged or sliding. Sliding gates are optimal, as they have the ability for partial opening, and should be a minimum of 1.8 m (6 ft) wide and 2 m (6 ft 8 in) high. If the gate uses a track, care should be taken in the construction of the track to avoid injuring the feet of the animals as they run through gates during introductions. Exterior building doors may be made of steel or wood reinforced with steel, with the lower part covered by a steel plate to minimize damage. Gates should be constructed to allow keepers to open and close them without entering rhino space. Also, where appropriate, vehicle access to an enclosure should be provided. There are a variety of options available to operate gates. The simplest systems are manually operated, either push-pull or cable driven. Rhino-size doors can be heavy and difficult to move. Mechanical systems can make this easier, using electric motors or hydraulic or pneumatic pressure to move the doors. These systems require some form of back-up system in case of a mechanical or power failure. Mechanical systems can generate significant forces that can injure or even kill an animal. Safety measures have to be incorporated into the design of the gate operating system to prevent accidents.
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Substrate
The outdoor enclosure should have a well-drained surface that provides adequate footing for rhinos. Greater one-horned rhinos require substrates that “give,” including mulch (such as hardwood), grass (irrigation should be planned for all natural areas if needed) and bedding because of the incidence of foot problems. Rhinos should be carefully observed upon introduction to a new substrate, as excessive ingestion of the substrate from feeding on the ground has caused impaction in other hind-gut digesters.
Water
Fresh, potable water should be available at all times. Water should be changed daily or supplied by an automatic-fill or continuous-flow device. Regular cleaning and disinfecting should occur at a rate that inhibits the growth of algae and bacteria. Water devices should be substantially constructed to prevent injury, upset, spillage or leakage.
Mud Wallows
All rhinos need access to pools and/or mud wallows for skin health, temperature regulation and behavioral enrichment. The size of mud wallows should be gauged by the number of animals in the exhibit so that ample room is provided for each individual. It should be noted that given a start, rhinos may construct their own mud wallows. Construction of wallows varies by institution and exhibit. Some facilities use a concrete basin or pool filled with substrate, while others simply dig out a section of the enclosure. If a concrete pool is used, it should have the ability to be drained when needed, but care should also be taken to protect the drain line from being filled with substrate. If a wallow is dug on exhibit, it should be situated in an area that will allow adequate drainage away from the wallow. It is also important that a good source of water be nearby to keep the area wet. Wallows are much easier to manage if the enclosure allows access for a skid steer or tractor with front loading bucket. Mud wallows must be actively managed. If the local soil does not create mud of a satisfying consistency, it can be adjusted with the addition of topsoil, clay or sand. Standing water in an animal area can be a potential USDA compliance issue. The wallow should be monitored for the growth of algae. If the algae cannot be removed by raking or scraping, it may be necessary to fill the area in to allow it to dry completely for several days, and then dug out again. Depending on the local environment, the substrate may need to be changed several times during a year to prevent contamination. Institutions in northern climates may need to fill in the wallow during winter months.
Pools
When a calf is in the enclosure, pools should be modified or drained to a depth of 0.45 m (1.5 ft) or less. Ramps are preferable to steps for entry into the pool. They should be placed in at least two or three locations around a pool, if not the entire perimeter, to ensure safe access in and out of the pool. Ramp slopes should be no greater than 15 to 20°. If steps are used rather than ramps, they should have a 20- to 25-cm (8-10-in) rise with a 41- to 61-cm (16-24-in) step. Note that multiple entries to a pool prevent it from being a “dead end” in the enclosure. In the design of slopes or steps, keeper access for cleaning should be considered. The pool substrate should be broom-swept concrete. Table 4.13 lists pool specifications for greater one horned rhinos.
Table 4.13. Specifications for exhibit pools.
Overall Size Depth Comments
Greater one-horned 37.2 sq m At least 0.9 m (3 ft); Recommended
(400 sq ft) optimally 1.5 m (5 ft)
Visual Barriers
Naturalistic visual and physical barriers (refuges) in outdoor enclosures may help decrease aggression by permitting animals to separate themselves from others if necessary during introductions or in a group situation. Barriers should be large and high enough to provide “safe zones” that allow an animal to pass from another’s sight but should not hinder public viewing. Types of visual barriers include deadfall, logs and boulders, as well as trees and natural plantings. Trees and plantings may be protected from rhinos by pipe caging, rock aprons or barrier fencing. If permanent physical structures are not available as barriers, dirt mounds may be used to give individuals additional visual barrier points in the enclosure.
Shade/Rain Shelter
Access to shade is a necessity as well as a USDA requirement under the Animal Welfare Act. A variety of both natural and constructed options are possible. It is also important that a shade option be adequate as a rain shelter if barn shelter is not always accessible, therefore, trees may not be completely adequate. Pools should be located in areas that are shaded at least part of the day.
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Additional Furnishings
Additional furnishings for the outdoor exhibit should include scratching posts, which may be particularly effective if placed near mud wallows or pools. Post materials must be non-toxic to rhinos (i.e., non-creosote). Several institutions have buried deadfall or logs upright in concrete sewer culverts, which are routed in place with 0.9 to 1.2 m (3-4 ft) of gravel. This enables managers to remove and replace posts as they deteriorate. Feed should be available at all times in the form of browse, feed stations and mineral salt licks.
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