What is a chameleon?
Chameleons are small-to-medium size reptiles famous for their ability to change colors suddenly and dramatically. Contrary to popular belief, a chameleon doesn't usually change colors in order to blend in with its surroundings. Rather, color is used to convey emotions, defend territory, and communicate with mates.
Other chameleon characteristics include bulging eyes that move independently of each other and feet set in a grasping position. Many species have horns or crests on their head. Arboreal species have prehensile tails used for grasping objects when climbing and moving. Some species have long extensible tongues for catching insects or small vertebrates, sometimes at a distance greater than their body length.
Chameleons are diurnal, solitary, and often aggressive toward members of their own species. Aggression is marked by rapid color change and hostile posturing. They're opportunistic hunters that wait for prey to pass within range of their long tongues. Chameleons have a peculiar way of moving in which they slowly rock back and forth between each step, often in time with the movement of nearby leaves blowing in the wind. Most chameleons lay eggs.
Where in the world have they been hiding?
Madagascar is home to half the world's approximately 150 species of chameleons, including both subfamilies: typical chameleons (Chamaeleoninae) and dwarf chameleons (Brookesiinae).
First discovered in 1893 and last seen in 1913, Voeltzkow’s chameleon (Furcifer voeltzkowi) was rediscovered in the Mahajanga region of northwest Madagascar, the most biodiverse area for chameleons on the island. It was discovered by Frank Glaw and his team from the Department of Vertebrates at the Bavarian State Collection of Zoology.
(A pair of Voeltzkow’s chameleons; photo by Frank Glaw)
From the start, the team had known the expedition would be a challenge. The Voeltzkow’s closest relatives, Labord’s chameleons (Furcifer labordi), live for only 4 or 5 months over the winter. Since winter in Madagascar is the rainy season when many roads become impassable, the team had a very short window of time to find the little reptiles.
But far from having to travel into dark, steamy jungles full of stinging insects and venomous snakes, more than 15 Voeltzkow’s chameleons were found in an unintended hotel garden in town during the final days of the expedition.
During most of the trip, searches in areas where the team had expected to find them had been entirely unsuccessful.
(Tiny enough to fit on the head of a match, Madagascar's smallest lizard, Image: PLoS One)
A colorful surprise
To everyone's amazement, the team found a total of three males and 15 females. All the specimens collected for study a hundred years ago had been males, significantly limiting the information available about the species.
When relaxed, both sexes are green with a few white and black markings. However, when stressed, angry, handled, or experiencing changes in hormones due to mating, they usually turn black-and-white striped with a line of three red dots along their back. They will also glow a shade of indigo and display a grid pattern of white, indigo, and black stripes.
Rediscovery of the colorful Voeltzkow’s chameleon has rekindled hopes of finding other species not seen since Woodrow Wilson was president. Scientists have a lot to learn about this extraordinary reptile, not the least of which is how to save it from extinction.
The discovery puts Voeltzkow’s chameleon on the growing list of Lazarus taxa species that are found in the wild years after science has declared them extinct. The International Union for the Conservation of Nature is the world authority on endangered species. It is the opinion of the discoverers that the Voeltzkow’s chameleon should immediately be reclassifsied as endangered rather than extinct based on the IUCN criteria. To date, IUCN has not published an official reevaluation on their Red List.
With the official discovery of Voeltzkow’s chameleon along with a series of rediscoveries in the last three years, one well-known global wildlife organization's "most wanted species" list has been reduced to 20. Among the rediscoveries are Jackson’s climbing salamander, Wallace’s giant bee, velvet pitcher plant, silver-backed chevrotain, Vietam mouse-deer, and Somali sengii.
How do chameleons change colors?
Chameleons have two layers of specialized cells that lie just beneath their transparent outer skin. The cells in the upper layer contain yellow and red pigments. Below that is another layer of cells containing a colorless crystalline substance that reflects the blue part of the light spectrum. If the upper layer is yellow, the reflected light becomes green (blue plus yellow). A layer of dark melanin is situated even deeper and influences the hue of the reflected light. All these different pigment cells can rapidly relocate their pigments, changing the color of the chameleon.