Flashy Lizards Attract More Mates ... and Predators

Like so many species, in the lizard world, the flashier ones are usually believed to be more appealing to potential mates. But that also means they’re easier to spot for predators. 

A new study tests this long-believed but little-researched assumption. Scientists found that even clay models of lizards with colorful dewlaps — flaps of skin under their chins — are more attractive to mates and predators.

“It's pretty well understood that having conspicuous or cumbersome sexual traits in general can draw the attention of predators. However, within a single sex, we know surprisingly little about how the variation of a sexual trait itself can influence predation,” first author Lindsey Swierk, an assistant research professor of biological sciences at Binghamton University, tells Treehugger.

In other words, Swierk says, researchers don’t know if the difference in how colorful or conspicuous those flaps are had an effect on predation risk.

“This is a really interesting question to me because, if dewlaps vary in just how ‘dangerous’ they are to bear based on their color, then there must be some benefit that outweighs the risk for these flashy traits to evolve,” she says.

For their study, researchers created clay models of water anoles (Anolis aquaticus), a species of lizard found in Costa Rica and a small area in Panama. They conducted their experiment at the Las Cruces Biological Station in Costa Rica. Using clay models allowed the researchers to change just the dewlap color while keeping all the other lizard traits, such as body size and shape, constant.

Some water anoles have bright red-orange flaps, others have a dull brown-red flap, and some have more muted colors. So they created clay lizards with similarly colored dewlaps.

“Using clay models to study predation allows us to track predation attempts easily: Once predators bite the clay lizard, they ‘realize’ their mistake and leave behind the model with the clay-imprinted record of the attack,” Swierk says.

They placed hundreds of these clay models throughout the lizard habitat, checking them every few days for bite marks, as evidence that they had been attacked by predators. The lizard models were made of soft clay, so each time a predator tried to bite them, they left an impression.

“We have many examples of bird beaks ‘stabbing’ the clay along the head or back of the clay lizard. We were therefore able to document any ‘attack’ on the clay lizards,” Swierk says. 

The results showed that the flashier animals really were more attractive to predators. The findings were published in the journal Evolutionary Ecology.

Although to people, the models might not look very much like lizards, they were authentic enough to fool predators.

“Predators use something called a ‘search image’ when they are hunting their prey — a set of basic rules that animals follow when classifying something in their minds. It's the same reason that a person might jump if someone sneaks a large plastic spider in their bed. Although a plastic spider doesn't really look that much like a real spider, for a moment a human's search image is fooled,” Swierk explains.

“So, in our case, we just needed to make the clay lizards look convincing enough to their predators to fool search images, which meant they needed to approximate the same shape and size of a lizard, particularly when viewed from above. Not only were predators at least initially ‘fooled’ by the models, but also some other lizards, too!”

Attracting Mates

If these flashier males have riskier lives, why do females prefer them over their dowdier counterparts?

Males of this species don’t offer any material benefits such as parental care to females, so all they get out of a mating relationship is genetic material (sperm), Swierk says. Because of that, females look for males with the highest-quality genes, so they can pass on those benefits to their offspring.

“Males that can advertise that they're healthy, have a great territory, and can defend their resources from other males are attractive to females because it's likely that they have really great genes,” Swierk says.

“In addition, males with especially conspicuous dewlaps have already survived a gauntlet of trials in their lives despite this costly and risky trait. It's been hypothesized that females may have evolved to prefer males with such flashy traits, because male genetic material must be high-enough quality to allow them to survive despite this risk.”