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Captive |
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Management |
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All Rhino Species |
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Cage restraints. Procedures such as ultrasonography, semen collection, and blood sampling often need to be conducted regularly and without the use of anesthesia.
Eight chutes in different zoos are compared, of which the final results are as follows:
Length
Chute length is a compromise between providing sufficient length for closing the endgates before the animal could escape and the need to reduce its forward movement once closed into the chute. Animals often refused to completely enter short chutes. These chutes were only as long as the nose-to-rump dimensions of the animal. Closing of the gate was also prevented when rhinoceroses stretched their bodies to obtain food without completely entering. Longer chutes provided enough time to secure the gates before escape but allowed excessive forward movement of the animals. Operators trying to contact the animal from the side were imperiled, whereas those working on the rear ran the risk of being dragged into the chute. Thus, forward movement had to be controlled in longer chutes. Less chute length was needed if the gate could be closed rapidly. However, retreating animals could be injured as the gate was being closed.
Methods of Stabilizing the Animal
Forward movement was reduced prior to chute entry by moving either a rear or front panel, but this required the animal to completely enter a shortened chute and remain standing for closure of the backgate. Eyres et al. [1995] reported shortening the chute after the animal entered by forward movement of a rear panel manually. This allowed adjustment for different-sized rhinoceroses and better control of the animal within the chute. A squeeze panel should not bind with pressure and should have an automatic release mechanism for use if the animal becomes wedged or excited. Unfortunately, squeezing mechanisms can push the head of the rhinoceros down into uncomfortable positions. As a consequence, shoulder restraints were developed as a more comfortable system for restraining rhinoceroses.
Restraining animals at the shoulder is commonly used for domestic bovids and has been used for some wild species. This method is effective because the rump-to-shoulder length remains constant, while the rump-to-nose length varies when the animal lowers its head. This restraint device is referred to as a 'headgate' and is usually snapped shut, catching the animal at the shoulder just after the head has passed through. The large body size of the rhinoceros precluded the use of headgates in this manner. However, rhinoceroses tend to back up once restrained, allowing placement of shoulder restraints.
Width
Chutes should be narrow enough to reduce side-to-side movement, yet wide enough to allow the animal to lie down but not roll over. Animals sometimes refused to enter chutes that were too tight (<10 cm on either side of the animal), or if they did enter, they sometimes became wedged when trying to lie down. In chutes with fixed sides, the width of the chute must be carefully coordinated with the width of the animal. Chutes with fixed sides that were too wide required wider rear openings in the endgate (access for palpation) to compensate for greater lateral movement of the restrained animals. Similarly, narrower chutes required proportionately smaller openings. With some chutes, the openings in the endgates could be made to correspond with chute width through the use of removable or adjustable bars.
Adjustable sides allowed flexibility in chute width and thereby accommodated a wider range of animal sizes and better control of the restrained individual. Adjustable chutes may create wedging problems, but these can be prevented by use of a pressure relief valve. Use of chutes with nonbinding adjustable sides could provide effective restraint of rhinoceroses.
Endgates
A variety of endgates has been used to facilitate the entering and leaving of chutes. Sliding doors may be operated manually or hydraulically. Hydraulic doors have the disadvantage of a slow response time. Freely movable manual doors can be opened or closed quickly but are dangerous to the door operator in situations in which the animal is able to slide the door with its head or body. Guillotine doors generally have a faster response time than sliding doors for stopping animals. They require a tall structure and must be counterweighted to prevent operator fatigue and to prevent the door from being accidentally dropped on the animal. None of these doors can be moved if animals are leaning against them, but a powerful hydraulic door could be more readily engaged under these circumstances.
Height
The low heights of some chutes allowed animals to climb on top of them. In addition, the animals took advantage of any features that would assist in climbing the structure. A height of 244 cm was sufficient to preclude climbing for all three large species.
Materials and Construction
Chutes were constructed of steel or aluminum bars or chains. Steel bars were most commonly used. Although aluminum is expensive and less malleable than steel, it produces less noise, and a quiet environment is particularly helpful during training of fractious animals. Bar diameters ranged from 6.3 to 15 cm. Small diameters were effective in holding animals, since only the weight of the animal was usually being supported. However, bars of this size can be bent by a charging rhinoceros.
Both vertical and horizontal bars were used in constructing chutes. Because rhinoceroses may sit on their haunches, positioning the anus only a few inches from the ground, operators performing rectal palpation were at risk when bars passed under the tail. A horizontal bar below the level of the anus must be very close to the ground or else the animal must be prevented from sitting or lying down.
Horizontal bars along the side reduced the likelihood of pinning the operator when animals moved back and forth but were in the way when the operator tried to reach under the animal to gain access to the abdomen or penile sheath. Vertical bars seemed to provide easier access but had to be widely spaced to prevent a foot from being caught if the animal rolled over on its side. This, in turn, created a large enough space for the animal to extend a nose and horn, presenting a problem if it was fractious or struggling. Narrowing the spaces was ineffective because the flexible toes of the rhinoceros could be worked into spaces as small as the size of the toenails, or a foot could be jammed into a space half the size of the foot pad. In other instances, these spaces were covered by panels.
A large, swinging gate in the Cincinnati Zoo chute provided easy access to the side of a Sumatran rhinoceros. However, gates of this type must not be wider than half the length of the animal, and the chute must be fairly narrow, or the animal can work its way out. Gates of this size should not be used if the animal tends to roll.
CONCLUSIONS
Permanent, indoor, pass-through chutes were the most efficient. Since rhinoceroses were exposed daily to these structures, they remained familiar with them. The animals could be loaded quickly, thus expediting procedures and allowing completion of several extensive projects. These chutes also were less stressful to the animals and reduced the time required to complete procedures. Some zoos have built dead-end chutes to comply with existing architecture. However, these chutes never efficiently handled the animals and were therefore inconvenient to staff. Such factors make major reconstruction of existing architecture worthwhile. Extending a building may be less expensive than hiring another keeper to make up for lost keeper time in maneuvering an animal. Ideally, construction of a chute should be planned along with construction of the holding facility.
The following features should be incorporated into a chute design. However. because of the variety of adverse actions exhibited by rhinoceroses. managers may be required to modify their chutes for particular situations.
1 The chute should be located indoors to permit use in any weather.
2. The chute should be designed in such a way that all procedures can be performed with the animal positioned either way.
3. The chute must be wide enough to allow animals to lie down but not to move excessively. Determination of appropriate width is critical in fixed-sided chutes. An average of 15 cm of space between the animal and the side of the chute is usually sufficient. The chute must be long enough (1 ? times the length of the animal) to allow the entrance gate to be closed before the animal backs out, yet short enough to prevent forward movement. Variation in width and length is best dealt with by squeezing the sides and ends of the chute. Shoulder restraints are a less expensive alternative to squeeze mechanisms. Shoulder restraints should be designed to accommodate the morphological characteristics of the species for which they will be used. They should also be quick releasing to facilitate the calming of agitated animals.
4. Squeeze mechanisms should not bind under pressure from the animal.
5. Endgates should open and close quickly. This can be accomplished by counter-weighted guillotine gates or freely sliding horizontal doors. Rhinoceroses must be protected from dropping doors, and personnel should be protected from sliding doors. Whether chutes are fixed or adjustable in width, the opening in the endgate should be as widely adjustable as possible and backed up by a solid door to prevent injury to the animal. The gate should contact the animal on muscle or fat pads to prevent injury.
6. Endgates should have openings large enough to allow access to the rectum or tail of the animal without impingement. This opening must be blocked by a solid door in circumstances when the head of the animal is presented.
7. Vertical bars should be spaced several centimeters farther apart than the diameter of the foot of the animal to be restrained. Small openings in the chute should be avoided because a toe or foot can be wedged into them. Removable panels may be an effective way to cover this space, but they are expensive. The cost may be reduced by the use of wood panels.
8. The height of the chute should be 60-90 cm higher than the height of the animal.
9. Access to light and electrical outlets and good drainage of water are advantageous.
Most of the custom designs we studied could ultimately be used effectively because of the nature of the animals and the efforts of staff. However, a commercially designed structure, built for the rhinoceros and including hydraulic doors, breakaway sides, removable panels, and sidebars, is available (C & S Cattle Handling Equipment, Cummings & Son, Inc., Garden City, KS). Another design that squeezes from both the sides and the rear is also available (Tod Ricketts, C.F. Jordan Inc., El Paso, TX). This design has removable side and end panels. These complicated chutes have been designed to deal with many of the problems described in this report but are expensive.
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Cage restraints for rhinoceros
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