Lizards develop new chemical signals for communicating when moved to a new environment, research suggests.
And they can do it rapidly and repeatedly if conditions are right.
“What we’ve discovered is that within species there is important variation in chemical signals depending on your context: who’s trying to eat you, who wants to mate with you and who you’re trying to compete with,” says Colin Donihue from Washington University, US, lead author of a paper in the Journal of Animal Ecology.
With colleagues, Donihue moved eight male and 12 female Aegean wall lizards (Podarcis erhardii) from a single source population in Naxos, Greece, to five small islets that lacked predators. Each was individually tagged, and the team returned over the next four years to check on them and their offspring.
They found that populations grew rapidly without predators, competition for resources became fierce, and on each island the lizards developed a new chemical “mix” that was distinct from that of lizards in the source population.
The changes were apparent after only four generations, and the researchers believe they have demonstrated evidence that lizards can “put on a new cologne” to suit their setting.
“Signals to attract mates are often conspicuous to predators,” says co-author Simon Baeckens, from the University of Antwerp in Belgium.
“As such, sexual signals present a compromise between attractiveness and avoidance of detection. However, on these islets, there is no constraint on the evolution of highly conspicuous and attractive signals.”
Lizards and snakes collect chemical cues from their surroundings by flicking out their tongues, then process those cues using a sensory organ in the roof of their mouths.
Lizards deposit their chemical messages encoded in secretions from specialised glands located on their inner thighs. The secretions are a waxy cocktail of lipid compounds that contains detailed information about the individual lizard that produced them.
How this works in a range of species needs more research, Donihue says.
Chemical signals are the oldest and most widespread communication mode, spanning bacteria to beavers, but scientists have focused more on acoustic and visual signals, he suggests, because they are more obvious to humans and easier to understand.
“Animals have spent over a billion years developing a complex chemical communication library, but we only invented the technology to identify many of those chemicals a century ago, and the experiments for understanding what those chemicals mean for the animals in nature have only just begun,” he says.
“We found that animal chemical cues can rapidly and flexibly change to suit new settings, but this is only the beginning for understanding what the lizards are saying to each other.”
Nick Carne is editor of Cosmos digital and editorial manager for The Royal Institution of Australia.
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