Holly Frisby, DVM, MS
Veterinary Services Department, Drs. Foster & Smith, Inc.
Genetic Differences
The predominant color of green iguanas is green, but can actually range from brilliant green to a pale blue-gray. There are genetic variations in the color of iguanas. Some can appear more brown in color, while others are almost a turquoise blue. Recently, albino iguanas have been bred in captivity. One strain of green iguana from South America has a reddish cast to the head.
Age Differences
Young iguanas are generally brighter green or blue with some dark brown striping on the body and tail. The striping pattern of some actually results in a reticulated pattern. This coloring helps to camouflage them as they live among the bright leaves in their natural habitat. As they age, the green color becomes less intense. The dark patterns, striping, or banding on their bodies and tails become more intense as the iguana reaches approximately 18 months of age. The heads of older iguanas tend to be paler, appearing gray or almost white, as seen in the iguana on the left.
Breeding Season and Dominance
Male iguanas develop an orange to orange-red coloring as breeding season approaches. In some iguanas, the orange color may be diffuse over the entire body. In others, the orange can be concentrated in several areas including the dewlap, spikes, body, and legs. Female iguanas can also develop this orange coloration, though it is usually less intense.
Dominant males and females often retain the orange color past the breeding season. The orange color will persist if there are other iguanas present, or even dogs, cats, and people, over whom the iguana feels dominant.
Environment
Environment, especially temperature can influence the color of an iguana. Iguanas tend to become darker if they are cold. The darker color helps them absorb more heat. Color change in response to temperature is called "physiological thermoregulation." In addition to the darker color, an iguana may develop dark, wavy lines on its head or body if it becomes chilled.
Iguanas kept in too warm of an environment may become lighter in color.
