Showy lizards are more attractive to mates and predators

In the world of lizards, the bright colors attract the interest of females looking for mates. But they can make colored males desirable for other eyes as well – like lunch.

Lindsey Swierk is the first author of an article in the magazine Evolutionary ecology on the subject. Called “The intrasexual variability of a conspicuous social signal affects the attack speed of lizard models in an experimental test,” the article describes an experiment involving clay models of aquatic anole (Anolis aquaticus), a species of lizard that found only in Costa Rica and a small slice of Panama. The researchers conducted the experiment at the Las Cruces Biological Station in Costa Rica, which is one of the Organization for Tropical Studies’ field stations.

To attract the attention of females, male anoles have dewlap – colored stretchable flaps of skin under the chin. In most anole species, dewlap have evolved to be as prominent as possible within the environment, given the predominant colors and lighting conditions of the environment.

“Even so, we see a lot of variation within a species in how bright the dewlaps are,” Swierk said.

While some water anoles have dramatic orange-red flaps, others have more muted colors, more of a dull brownish red. The researchers wanted to determine the effect these color variations had on predation risk.

While it is widely believed that flashier males attract more attention from predators, few studies actually test this hypothesis. Logistics may be a factor: Researchers must separate the effects of sexual colors from other aspects of a creature’s body and behavior, a difficult task when using real animals. Consequently, many studies show correlation but not causality.

To show that flashier males face greater risks of being attacked, the researchers created clay models with colorful dewlaps, some bright, some more subdued. Many visual predators use a stereotypical “research image” to identify prey, so the models only needed to approximate the anole’s overall size, color and shape. The color of the dewlap, however, required special attention.

“Because different animals have different visual sensitivities than we humans have, getting the colors right was an important consideration in our model design,” explained Swierk. “We ran some pilot tests prior to this experiment to make sure our models were as convincing as ‘lizards’ – and they certainly seemed to be, as many birds and other lizards bit them!”

The researchers were able to identify predators by bite marks in the clay models. They included many bird species, including the beautiful motmot with its serrated beak. Basilisks and whip-tailed lizards were also among the likely attackers. The results showed that flashier lizards actually end up for lunch more often.

If bright colors have deadly consequences, why do female anoles prefer them? One answer is that the brightest males have high-quality genetic material or resources that allow them to manage the risk of being eaten, Swierk explained.

“Since the evolutionary ‘mission’ of every individual in life is to pass on as many copies of their genes as possible, conspicuous traits like these can evolve if they give an individual a high level of reproductive success, even if the flashy trait ends up killing. eventually, “Swierk said.