Male Jackson's chameleon
Female Jackson's chameleon
They are sometimes called three-horned chameleons because males possess three brown horns: one on the nose (the rostral horn) and one above each superior orbital ridge above the eyes (preocular horns), somewhat reminiscent of the ceratopsid dinosaur genus Triceratops. The females generally have no horns or traces of the rostral horn (in the subspecies T. j. jacksonii and T. j. merumontanus). The coloring is usually bright green, with some individual animals having traces of blue and yellow, but like all chameleons, they change color quickly depending on mood, health, and temperature.
These are small to medium-sized chameleons. Their adult size is 12 inches (30 cm) in total length. They have a saw-tooth shaped dorsal ridge and no gullar crest. They attain sexual maturity after five months. The lifespan is variable, with males generally living longer than females.
Jackson's chameleons live primarily on a diet of small insects. They are less territorial than most species of chameleons. Males will generally assert dominance over each other through color displays and posturing in an attempt to secure mating rights, but usually not to the point of physical fights.
Jackson's chameleons are native to the humid, cooler regions of Kenya and Tanzania, East Africa, and found in great numbers at altitudes over 3,000 m. The subspecies T. j. merumontanus can only be found on Mount Meru and the Arusha Region of Tanzania. The subspecies T. j. xantholophus was introduced to Hawaii in the 1970s and has since established populations on all main islands. This population was the primary source of Jackson's chameleons for the exotic pet trade. However, the exportation of these animals (and many others) from Hawaii for the pet trade has been made illegal to prevent opportunists from willfully establishing further feral animal populations to capture and sell them.