The Meller’s chameleon, Trioceros melleri, also known as the “giant one- horned chameleon”. The Meller’s Chameleon is one of the largest in the world. They can be up to two feet long and weigh over a pound. While almost half of chameleon species live in Madagascar, the Meller’s is the largest species outside of Madagascar and lives in Tanzania, northern Mozambique, and Malawi. Their habitat is tropical grasslands and savanna treetops. Chameleons are in possesion of many unique, and even bizarre adaptations that set them apart from other species: Their feet,eyes tongues,skin and in the case of the Meller’s Chameleon, the small horn at the tip of their snouts.
Chameleons actually have five clawed digits, however they are arranged almost like a mitten with three digits grouped together on the inside and two on the outside on the front feet and the opposite arrangement on the back feet. This arrangement along with swiveling wrists and forearms allow the chameleon to grip branches.
Chameleon’s unique eyes allow them to view almost 360 degrees. The eyes are on opposite sides of the head and mounted on conical turrets. A thick fused eyelid keeps the eye protected and secure within shallow sockets while also allowing for the turret’s wide range of motion. Chameleons can also alternate between monocular and binocular vision. While searching for prey, they use monocular vision: each eye moves independently, utilizing a panoramic view to scope out prey. Once prey is found, the chameleon can then switch to binocular vision: neurons from the eye that sees prey synch with those that don’t forming a neural bundle. The eyes then are able to both fix on the prey item and only the head moves.
The Chameleon’s tongue is perhaps its most iconic adaptation. A chameleon’s tongue can be up to 1 ½ times the length of the animal’s body which, for the Meller’s Chameleon can be up to 20 in. It is anchored by a U-shaped hyoid bone. The tongue is hollow and the retractor muscles fold around a cartilaginous hyoid horn like an accordion. When the chameleon is about to strike, the hyoid bone moves above the lower jaw and forward. Muscles essentially squeeze around the tongue forcing it out of the mouth (like the example of squeezing a watermelon seed between your fingers). Lubricated cavities in along the muscle reduce friction and allow the tongue to move smoothly and quickly. The tip of the tongue is club shapes to increase surface area and is rough and covered in sticky saliva which helps it adhere to prey. The Meller’s Chameleon, like all other species, is purely carnivorous and eat mainly insects (as seen in this video). Because of their large size, Meller’s chameleons can even eat small birds in the wild and in zoos are sometimes fed mice.
Contrary to popular belief, chameleons do not change their colors purely for camouflage and in fact many species display vibrant colors that would make them stand out rather than blend in. Instead, chameleons change color in response to stress, temperature, and mood. Meller’s chameleons color in mainly a dark green with dark spot and yellow to white stripes. While their resting coloration can help them blend in a bit with their surroundings, their coloration is mostly key in communication. Meller’s chameleons in particular undergo rapid color change as a form of communication of aggression, submission, reproductive status, ect. Because they are solitary and incapable of significant vocalizations these color signals are very important. A shift to a darker base color and more intense dark spots can signal stress while a lighter coloration can signal excitement. They can also take on darker colors in warmer temperatures and lighter colors in cooler temperatures. Male Meller’s chameleons will turn red during the mating season. A receptive female will turn a yellowish color and an uninterested female will turn grey or black. The color change is the result of specialized cells called chromatophores. The chromatophores are attached to small muscles that can stretch the cell in response to brain signals. This change in shape alters the distribution of pigment in the cell which on a large scale, with many cells creates the overall changes in skin coloration.
One of the key characteristics of the Meller’s Chameleon is the small horn at the tip of its snout. This horn is used by males to compete for mates along with their prominent helmet and dorsal crests that also aid in communication, specifically in disputes between males and mating.
Meller’s Chameleons are particularly susceptible to stress. As a result any environmental change has a huge impact and habitat destruction and the pet trade have put a strain on the species.