On predator-free Greek islands, male lizards are learning a new language of love, developing a sweet-smelling chemical cocktail unknown on their home island to entrance lady lizards, and it’s happening astonishingly fast.
Most animals experience a trade-off when it comes to mating. It’s important to get yourself out there so potential partners can see what you have to offer, but to predators what you offer is a tasty meal, so advertising for a mate can draw their attention. If fate takes you to a place where such threats are unknown, however, you can really let your inner show-off rip.
This is what has happened to a set of fortunate Aegean wall lizards (Podarcis erhardii). The lizards are native to Naxos in Greece, where many predators force them to keep a low profile. Zoologists decided to see how the lizards would evolve if transported to five nearby small islands where resources are scarce but predators non-existent.
In the Journal of Animal Ecology the team reports the population predictably boomed in the new homes, rising fivefold in four years. Moreover, it took just four generations for the male lizards to start creating stronger scent profiles to attract females.
P. ehardii produces a waxy mix of lipids from glands on their inner thighs. These are attractive to the females, telling them something about the males’ qualities. However, some lizard-eating Naxos snakes hunt by smell, making any male who smells too strongly vulnerable.
Within four generations the reptiles on all the small islands were producing a more complex chemical mix than their counterparts in their predator-infected homeland with larger quantities of three compounds known to be associated with mating. The authors refer to this as “putting on a new cologne”. Moreover, the change was consistent across each island, indicating selection pressures, not a random shift.
“In the experimental islands, we found that the ‘signal richness’ of the lizard secretions … meaning that the number of different compounds that we could detect in the secretion is the highest,” Dr Simon Baeckens of the University of Antwerp said in a statement.
Life wasn’t entirely idyllic for the transported males, however – they were twice as likely to carry bite marks from other lizards than on Naxos.
“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,” Dr Colin Donihue of Washington University, St Louis said.
Species known to produce a fancy “perfume” to attract a mate includes crested auklets and ring-tail lemurs. In contrast studies of visual and acoustic signaling in animals are common. Humans have much better eyesight and hearing than we do smell, so we have tended to study the things we can see and hear.