are large, heavy-bodied lizards with equally large and complex personalities, and substantial space requirements. They can live for more than 60 years, and owners must commit to decades of daily care, personalized attention and financial responsibility. There are no shortcuts when it comes to keeping these magnificent creatures healthy. The basis for their captive husbandry is best derived from research into their natural history, and dedicated caretakers will continually refine their setups as new information is discovered.
Rhinoceros iguanas (Cyclura cornuta) occur on the island of Hispaniola, which contains the Dominican Republic and Haiti, in dry thorn forest habitat with sand, coral or eroded limestone substrates along coastal terraces and lowlands. Species distribution is widespread but disjunct with the highest concentration in the Dominican Republic’s Southwest, where they occur sympatrically with Ricord’s iguana (Cyclura ricordii).
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Rhino iguanas by John Binn.
Adult male rhinoceros iguanas can reach a snout-to-vent length of 22 inches with a weight of 13 to 22 pounds. Females are smaller and lighter, reaching 20 inches SVL. Sexual maturity in females generally occurs when they’re 2 to 3 years old. For males it is unknown, but the same age range is suspected.
In the wild mating occurs in May, and oviposition takes place during the dry period from mid-June to mid-July. Hatchlings appear from mid-September to mid-October during the heavy autumn rains, which produce fresh vegetation for the youngsters.
The rhinos’ natural habitat is filled with retreats in rocky crevices as well as sand and fossil-coral substrate in which the iguanas dig burrows. As with all rock iguanas, retreats are crucial for shelter, seclusion and protection against predators.
The diet is herbivorous and consists of more than 70 different plants, including leaves, flowers, and natural tree and shrub fruits. Rhinos will consume some animal matter, particularly seasonal caterpillars and pupae; however, their daily diet is plants. The consumption of animal matter is opportunistic and infrequent. Rhinos drink, or lap, rainwater or fresh water when available.
The average annual temperature in areas supporting rhino iguanas is 87 degrees Fahrenheit. The historic average low temperature is 63 degrees, and the high is 93 degrees. Average annual rainfall ranges from 19 to 40 inches. Elevation in these areas is from 115 to 1,312 feet.
Room to Roam
Weighing about 20 pounds with a body close to 22 inches SVL, an adult rhino iguana requires considerable space. Unlike the arboreal green iguana, which favors height, the rhinoceros iguana is terrestrial and needs to roam. Ideally, a large outside pen in the most southern areas of the United States is best. When this isn’t possible, configuring a smaller enclosure requires creativity to provide the necessary space required.
Compressing the size of an adult rhino enclosure to fit available space creates a host of problems. Undersized enclosures might not evacuate heat generated by color-corrective, UVB and basking lamps, preventing the establishment of an acceptable temperature gradient. Space for animal and enclosure amenities is limited as is the availability of low-wattage bulbs to compensate for the small enclosure size. Smaller enclosures are also more difficult to keep clean. Most importantly, insufficient area for the animal to move about freely commonly results in neurotic behavior and aggression. The only appropriate solution is to have a second larger area where the iguana is moved daily for exercise, human contact, change of environment, sun exposure, etc.
Commercially available reptile enclosures are not designed to accommodate a large adult rhino iguana. Many sacrifice floor space for height and are best suited for arboreal reptiles. A rhino enclosure should be the exact opposite, and usually it must conform to an existing room, garage, enclosed patio or outside shed to maximize the enclosure size. The solution is to either design a custom indoor enclosure or partition an area within the home.
A partitioned area provides more configuration options, and simplifies control and management of environmental requirements. Locating the enclosed area next to a window takes advantage of natural sunlight, reducing the need for artificial lighting and lowering utility expenses. Wide-pitched-mesh window screening maximizes UVB penetration, and screened areas can be extended into a garden area for basking. Outfitting a partitioned area with lighting, UVB, heating, a retreat, multileveled perches for exercise and other amenities is relatively straightforward.
The most technically challenging containment option is a custom indoor enclosure. Generally, one would determine the size of the box to fit the space, build it, and then install environmental and other enclosure necessities. This approach works for an indoor enclosure of sufficient size.
However, if limited space necessitates compression, designing from the inside out is the best option. It helps to address the issues previously mentioned and ensures proper function before resources are expended on construction. The initial steps when designing from the inside out are to assemble the desired lighting, create a simple low-cost enclosure mock-up, install the fixtures, and begin measuring temperatures and UVB levels. Make adjustments to the mock-up to improve performance by moving fixtures, creating exhaust vents for heat or to improve air circulation, or changing lamp wattages.
The next step is simulating the placement of amenities to ensure sufficient area for the animal. The amount of space adults need depends on where they’ll be kept. Outdoor enclosures should be 10 feet long by 8 feet wide by 8 feet tall (80 square feet), or a smooth-skinned, cement-walled pen at least 45 inches tall. Indoor partitioned areas should be a minimum of 7 feet long by 6 feet wide by 8 feet tall (42 square feet). Boxed indoor enclosures should be a minimum of 7 feet long by 4 feet wide by 5 feet tall (28 square feet), and this option requires an additional, larger daytime holding area.
Large commercial enclosures (terrarium or box) are fine for juveniles and subadults as long as they have a screened top on which to rest or mount a color-corrective lamp, UVB lamp and heat fixtures. They also must have adequate ventilation and provide room for the rhino to grow. An 80- to 100-gallon glass terrarium or a framed, vented box measuring 4 feet long by 2 feet wide by 2 feet tall would be sufficient for a rhino up to 3 years old. Beyond that, a custom enclosure is needed.