In the course of research to understand the relationship between body-color patterning and mating behavior in the fence lizard Sceloporus undulates, researchers found that male lizards tend to stay away from "bearded" female lizards.
The sex lives of the fence lizard Sceloporus undulates are not as simple as you think. These reptiles have a complicated system of attraction and mating. The male species are characterized by ornamental blue "badges" on their throats and abdomens. Previous studies have linked this blue coloring to testosterone and it comes as no surprise that these "badges" are used in courtship displays and in aggressive encounters with rival males.
Tracy Langkilde, an associate professor of biology at Penn State University, and Lindsey Swierk, a graduate student in Langkilde's lab, conducted a study to better understand the relationship between body-color patterning and mating behavior in these lizards. Most of the female lizards of this species also sport a blue colored "beard" - hence the name "bearded ladies."
From the study, researchers found that the male lizard is less attracted to female lizards that sport a brilliant blue colored beard compared to those that have a duller beard, thus having less testosterone. Researchers clarified that in spite of this, the male lizard wasn't all that choosy. They didn't completely turn away "bearded" female lizards, they just preferred the ones with less coloring.
"We found that, although males do not say 'no' to bearded ladies, they clearly discriminate against blue-ornamented females, opting more often to court females without coloring," said Swierk in a press statement, according to Eureka News.
One reason for this preference could be an evolutionary one. Researchers found that female lizards with less coloring were more likely to lay heavier eggs with more nutrients. They also laid eggs earlier in the season, giving their brood more time to develop, thus increasing their survival chances.
This finding gave rise to another question - if the bearded ladies weren't laying eggs that were viable, why were they so predominant? According to statistics, breaded ladies account for 75 percent of the female lizards in some populations and 95 percent in others. Researchers found that several factors contributed to this - one being that the sexual lives of fence lizards are in a period of evolutionary flux.
"It is possible that we're catching a snapshot of the evolutionary process-[that] bearded ladies are very slowly being 'selected out' of the population," said Swierk in an emailed response to National Geographic.
Another explanation could be that bearded ladies were more dominating and hence, more likely to get their "man."
"Bearded ladies also may be more sexually aggressive so, although the males don't prefer them, they may initiate more of the courtship and mating and produce as many or more offspring for this reason," said Langkilde, who also responded to questions by email.
Unlike the male species, female fence lizards find the blue coloring very attractive and generally pass on their blue beard to their male offspring, thus keeping their genes alive.
