Beyond more attractive smells or brighter colors, male binder lizards can use other strategies to achieve reproduction when they are in unfavorable circumstances.

A pair of folder lizards in the Sierra de Guadarrama in Madrid.

Folder lizards can use reproductive strategies to choose the best males to ensure in this way the quality of their offspring, according to an investigation by the National Museum of Natural Sciences (MNCN-CSIC) published in the magazine Behavioral Ecology. According to scientists, sexual cues help females choose the best males, but it may also be the case that less attractive individuals follow alternative reproductive strategies to achieve reproduction.

For example, beyond sexual signals such as more attractive smells or brighter colors, male folder lizards, Iberolacerta cyreni, they can use other tactics when they are in unfavorable circumstances. Specifically, researchers have detected how this species uses the so-called Terminal Investment Strategy for which an animal with little chance of survival and future reproduction, invests all its effort in trying to copulate in the present.

The work shows how some males with poor quality signals they would use different strategies to those of higher quality males, achieving similar reproductive success in a specific season, although their overall success throughout their lives remains lower. Signage visual, chemical and auditory it is one of the essential forms of sexual communication in the animal world.

“The females, attracted by certain characteristics of the different signals, would choose the healthier males with better genes and thus the probabilities that their offspring are of good quality would increase ”, contextualizes the MNCN researcher Gonzalo Rodríguez-Ruiz.

This choice hides a reliable way of evaluating quality, since only males with good health and sufficient resources can bear the cost of expressing high-quality signals. The production of colorful ornaments or suggestive smells is very expensive in energy terms and resources.

“For example, in the case of the chemical signals of the Carpena lizard, producing a quality signal implies using compounds necessary for its immune system, such as vitamin D“, Clarifies the MNCN researcher José Martín.

The female is brown and the male is green, and this relationship between sexual signaling and male quality has been proven in numerous studies and in many faunal groups. Those males that are capable of producing better signals have a greater number of offspring thanks to the fact that they are able to attract more females.

“What is not so clear is that this is the only way to obtain reproductive success or if there are other strategies to reproduce. when there is no possibility of producing attractive signals“Explains Rodríguez-Ruiz.

The experiment

In this study carried out in the Sierra de Guadarrama, the MNCN team has explored how would a disease affect that prevents the production of sexual signals to the reproductive success of the lizards.

“What we did was activate the immune system of a group of males by injecting a bacterial lipopolysaccharide; that is, we simulate a non-existent disease that did not have harmful effects but that forced males to allocate resources to their immune systems instead of allocating them to the production of sexual signals ”, explains José Martín.

The results show that the simulated disease had a effect on resources devoted to sexual signalingFor example, the amount of provitamin D in the chemical signals of apparently sick males was lower than in healthy males.

It was also confirmed that, regardless of health status, the males that produced the best signals were those that more females fertilized and they had a greater number of offspring.

The weak male tactic

The data also showed that the larger size, or age, of the male is related to reproductive success in healthy males. “On the contrary, this effect was not found in sick males, but rather, in this group, males with greatest reproductive success were the small“, Points out Rodríguez-Ruiz.

In this way, Martín points out that the investigation concludes that there is a alternative behavioral strategy in the weaker males. It is the aforementioned Terminal Investment Strategy by which a sick animal, and with little probability of reproduction, tries to compensate for the absence of attractive signals by investing all its effort in trying to copulate, “Even if this costs him his life.”

Thus, the work points out the existence of alternative reproductive strategies that, without being based on sexual signaling or on the evaluation of the partner by the female, can be successful in some cases by allowing not only the strongest and healthiest individuals reproduce.