Study: Female Lizards Have It All
By Jennifer Viegas, Animal Planet News
Nov. 7 — A study of a particularly promiscuous breed of lizard reveals that the females try to have it all: they'll pair with males that control impressive territories, while still benefiting from mating with hearty male hunks on the side.
The study, published in the current Proceedings of the National Academy of Sciences, adds to the growing body of evidence that females throughout the animal kingdom, including humans, exert far more control over the mating process than was previously believed.
In the wild, large, dominant male lizards tend to control better territories. For this study, however, researchers artificially manipulated territories of male side-blotched lizards, Uta stansburiana, by giving even the smallest, scrawniest of males nice rock outcroppings with plenty of cozy nooks and crannies. During the three-year study, Ryan Calsbeek of the Center for Tropical Research at UCLA, and his colleague Barry Sinervo, moved over 1500 pounds of rock per year by hand.
Near the end of the breeding season for each year of the study, the researchers took note of the pairs. Females almost always chose males with the best rock homes, even if the males were smaller. Large size normally is a desirable trait in male lizards.
Some of the females were then captured and taken to a laboratory where they laid their eggs in a controlled, incubated environment. DNA analysis of the resulting offspring revealed that the females had mated with other, larger males, and reserved their sperm for producing sons. The smaller lizard's sperm was used for producing daughters.
Calsbeek said, "Behaviorally it looks like from our data as if territory quality is the key aspect of the female's choice. After all, the female moved away from her original choice of mate to live on a good territory despite the small male living there with her. However, further investigation using genetic tools allowed us to see that females were still getting to mate with her original choice of male. So it looks like females can have their cake and eat it too."
He added, "It's really an amazing degree of female control in the mating system. More so than we ever thought possible."
Bruce Lyon, assistant professor of biology at the University of California at Santa Cruz, concurred and said, "We are just now beginning to realize how females are paying extremely close attention to the quality of their sires and to sex ratios. There is even a species of warbler that seems to be able to consistently control the sex of its brood."
The study also indicates that all males have a chance in the mating game.
Lyon explained, "The good news for males is that both large (high quality) and small (previously considered to be low quality) males are attractive to females, just for different reasons."