14 DAY TRIAL // It seems easy for females: they are passive, just waiting for the pretenders and choosing the one that pleases them. But that is not always true, at least for female iguanas.
A team led by Maren Vitousek of Princeton University discovered that female Gal?pagos marine iguanas wasted a lot of energy picking a mate from a wide pool of suitors, an energy they could have otherwise spent on foraging, producing eggs, or to avoid predators. It was generally believed that the selectiveness of the females comes at a low cost for them.
And this especially when male territories are grouped together in "leks" (arenas), which allow females to appreciate many candidates' fitness without moving too far.
The research team assessed the energy amounts spent by the female iguanas on mate choice in the wild employing tiny data loggers developed by Anthony Woakes at the University of Birmingham. The females were found to burn an amazing amount of energy for picking males from a lek, even if her only gain was the genetic material from the chosen one. Mating with "attractive males" (those which show off more vigorously) appeared to be the most costly.
More time the females passed in the company of these hunks, more energy they burn, producing smaller eggs. Moreover, this drops their chances for survival. During El Ni?o, food turns scarce and those starting the season at a low body weight have minimal chances to survive.
Thus, the genetic payoffs offered to females by their chosen mates must overcome the energy expense. Ongoing investigation is going to assess these benefits in order to explain this high energy outlay.
This is one of the first evidence that selection for a desirable partner can involve energy expenditure also from the females, explaining better their being choosy, the sexual selection drive evolution and the war of the sexes.