Chameleons, introduced to Hawaii in 1972, began to parade in brighter colors, probably because they have fewer predators to hide from.
May 11, 2022
Kenyan chameleons, which were introduced to Hawaii half a century ago, have developed brighter colors, probably because they have fewer predators to hide from.
Jackson’s Chameleons (Trioceros jacksonii xantholophus) are native to Kenya and, like other chameleons, change color depending on their context.
Males turn yellow to attract females or signal their dominance to other males. They turn green and brown at other times to blend in with the vegetation and go unnoticed by birds of prey and snakes.
In 1972, about 36 Jackson chameleons were imported from Kenya by the owner of a pet store in Hawaii. He placed them in his back garden, but they fled. Because Hawaii has few animals that can plunder them, they have been able to settle widely.
Martin Whiting at Macquarie University in Sydney, Australia, and his colleagues wondered if the release of this predatory pressure had led to changes in the chameleon’s color displays.
To test this, they conducted experiments using Jackson’s male chameleons collected from Hawaii and Kenya. They expose each individual to another man, woman, model bird and model snake, and then observe their color changes in response.
Hawaiian and Kenyan chameleons turn yellow when they meet another man or woman, but Hawaiian yellow was about 30 percent brighter when measured by an instrument called a spectrophotometer.
When exposed to bird and snake patterns, both groups changed color to blend in with the environment, but Hawaiian chameleons made it less effective.
Hawaiians have probably gotten worse at camouflage because they don’t need it anymore, Whiting said. “That’s how natural selection works – if you don’t use it, you lose it.”
Because predators are mostly outside the equation, chameleons may have developed brighter yellow displays to increase their chances of attracting mates and breeding, he said.
This evolution occurred in only 50 to 65 generations, which is “quite fast,” says Whiting. “But it’s becoming increasingly clear that evolution can happen in much shorter periods of time than we previously thought.”
Other studies, for example, have found that lizards can develop longer legs within six months of experimentally introducing new islands.
Reference journal: Scientific achievements, DOI: 10.1126 / sciadv.abn2415
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