Chameleons become more visible when they have fewer enemies
No danger – no need for disguise? This seems to refer to male three-horned chameleons that have been transferred to another habitat.
Apparently, with fewer predators in their habitat, some male chameleons develop a more flamboyant play of colors. The researchers write about this in the journal Science Advances.
They had three-horned chameleons (Trioceros jacksonii) observed on the Hawaiian island of Oahu. They were introduced in 1972 for the pet trade from Kenya and then spread into the wild without much threat from predators.
Scientists from the Australian cities of Sydney, Canberra and Melbourne and from the Hawaiian island of Honolulu have now compared the chameleons from Oahu with their relatives from Kenya. To do this, they pitted males against other males, predators such as birds and snakes, and observed them during courtship. Oahu’s chameleons displayed more conspicuous colors when courting and competing with other males, and they were less camouflaged in the presence of predators.
Rapid evolutionary progress?
The study concluded: “The color display of male chameleons had a higher luminance contrast compared to the local background than that of Kenyan chameleons.” The effect is the same: more attention from potential sexual partners.
Because there are few natural predators for three-horned chameleons on Oahu, they are “less camouflaged than Kenyan chameleons when threatened by both bird and snake predators,” the study says. According to the researchers, these changes in just 50 years after their appearance may indicate rapid evolutionary progress and rapid adaptation.
How animals deceive, warn, lure
However, the authors also emphasize that, theoretically, the differences can also be related to the so-called founder effect. This would be the case if the animals imported to Hawaii were already genetically different from the original population in Kenya, for example because special animals were selected for trade. However, this seems unlikely to researchers, as the differences between Hawaiian and Kenyan chameleons point to a real adaptation to the new environment.