<em>By
Caitlin Capistron
Animal Keeper I
Honolulu Zoo, Honolulu, HI</em>

<strong> Introduction and Background</strong>

Foot problems are a relatively common occurrence in captive rhinoceros, and while vertical nail cracks can resolve on their own, intervention can decrease the healing time, prevent further problems from developing, and provide for a positive training interaction for the animal (Jacobsen, 2002).

The Honolulu Zoo houses 1.1 black rhinoceros and recently housed 1.0 white rhinoceros (<em>Ceratotherium simum</em>). The black rhinoceroses are exhibited together year-round in a 1,022 square meter [11,000 square foot] compact dirt yard, and were housed separately overnight in 56 square meter [600 square foot] barns with concrete flooring.  The white rhinoceros was exhibited in a 3,057 square meter [32,900 square foot] compact dirt mixed-species exhibit with 2.2 reticulated giraffe (<em>Giraffa camelopardalis</em>) and 1.1 Grant’s zebra (<em>Equus burchelli</em>), and had access overnight to a 53 square meter [570 square foot] barn with concrete flooring, a 73 square meter [780 square foot] pen with compact dirt, and the exhibit.

Since acquisition of the male black rhino, Corky, in 1999, he has had periodic foot problems, specifically vertical cracking of the lateral nails. Foot problems have not been noted in the female black rhino, Satsuki, or the male white rhino, Kruger. Treatment of Corky’s feet was opportunistic at best, and involved application of antiseptic solutions. Nail cracks would appear to grow out, though reoccur frequently. When cracks occurred again in June 2010 on the lateral nails of Corky’s front right and rear left feet, the splitting was more extensive, and extended the full length of the nails up to the coronary band (see Photos 1 &amp; 2). Honolulu Zoo Veterinarian Dr. Ben Okimoto consulted with veterinary staff at the White Oak Conservation Center, San Diego Wild Animal Park, and St. Louis Zoo to determine a treatment plan.

<img class="alignnone size-full wp-image-2658" title="rhino_feet" src="http://aecetia.net/gws/aazk/wp-content/uploads/rhino_feet.jpg" alt="rhino_feet" width="1000" height="404" />

It was hypothesized that a primary reason that Corky was experiencing foot problems, and the other rhinos were not, was related to Corky’s overnight housing. In contrast to our other two rhinos, Corky defecated in his barn then appeared to pace in his barn overnight, thereby covering his feet in wet fecal matter. Nail cracks can develop when the natural waterproof layer of the hooves (periople) is disrupted by excess moisture or dryness. We believe that excess moisture, in combination with a thinning of the nail walls caused by lying on concrete and compact dirt surfaces, compromised Corky’s nails. Mineral deficiencies were also considered, but because Corky was not yet trained to accept voluntary blood draws, we were unable to pursue this possibility in the short-term.

<strong>Husbandry and Treatment</strong>

Starting in November 2010, Corky’s overnight routine was changed. He was given access to one 28 square meter [300 square foot] barn stall, but rather than locking him into the barn, he was given overnight access to the exhibit yard and a 40 square meter [485 square foot] pen with compact sand. It was noted immediately that not only was Corky not pacing overnight in fecal matter in the barn, but also he was calmer overall.

For all foot treatments, a minimum of two people was utilized. Usually, a volunteer focused on feeding Corky his daily produce ration while a keeper worked on Corky’s nails. In most cases a third person, usually a volunteer, fed Satsuki at some distance from Corky and attempted to keep her from interrupting with Corky’s treatment. Our set-up to work with the black rhinos consisted of nine meters [30 feet] of vertical bars placed about 0.2 meter [nine inches] apart at the rear of the exhibit (see Photo 3). While we had some success with stationing Satsuki perpendicular to the bars at one end and stationing Corky parallel to the bars at the other end, this arrangement required the rhinos to be in close proximity to one another. Additionally, in order to access both sides of Corky, he was required to turn around and reposition, and brought him in even closer proximity to Satsuki. This often resulted in Satsuki bullying Corky away from the area to monopolize treats and attention. To address this issue, the decision was made to repair a door to a four square meter [41 square feet] chute that up until this point had not been utilized by rhino keeper staff. Once the chute door was repaired, Corky could then enter the chute from the rear of the exhibit, and a set of vertical bars placed 0.3 meter [one foot] apart on both sides would allow staff to access both sides of Corky’s body (see Photo 4). Additionally, since there was no need for Corky to reposition and be near Satsuki, it reduced negative interactions with Satsuki and the overall time the treatment took. While Corky was nervous at first to enter the chute, staff was careful to work at Corky’s pace and keep his experience with the chute a positive one. Once Corky was comfortable entering and stationing calmly in the chute, one person fed Satsuki at one end of the exhibit bars while another two people worked with Corky positioned in the chute.

Our foot care routine consisted of cleaning the nail cracks at least once daily: rinsing any mud and fecal matter off with water, then flushing the crack with hydrogen peroxide, then flushing the crack with Nolvasan®, then applying Betadine® to the crack and surrounding area. Approximately every two weeks, or as staff time allowed, corrective trimming was used to relieve pressure on the crack and to facilitate its correct growth. Fortunately, one of our Mammal Department supervisors…
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