Movement Rates in Anolis carolinensis Redux (Or) We Need to Study Female Anoles!

Some months ago, I posted a quick analysis of a dataset from 2010 on the movement rates of green anoles (Anolis carolinensis) in the presence and absence of brown anoles (Anolis sagrei) on spoil islands in Mosquito Lagoon, FL. At Jonathan Losos’s urging, Yoel Stuart and I turned this blog post into a paper, which was recently published in Breviora.

The story has not changed since the blogpost (though the analyses are now slightly more sophisticated): male and female green anoles seem to respond differently in their movement behaviour to the presence of brown anoles. There are many possible reasons for these differences, discussed in the paper, that can be summarized as “variation in the motivation for movement between the sexes.” Do read the paper if you’re interested in further details, but be forewarned that we engage in quite a bit of speculation because of one simple fact: compared to what is known about movement rates of male anoles, we know much less about how movement rates in female anoles vary with microhabitat.* Similar disparities between what we know about males and females exist in other aspects of anole biology too.

Though the subject matter of our paper is rather niche (anole ecology pun intended), it contains one paragraph that I think is more broadly pertinent:

 Much more attention has been paid to the behavioral ecology of male anoles than to that of female anoles (Butler et al., 2007; Losos, 2009). Our results suggest that male and female anoles can differ in their behavioral responses to ecological pressures. Understanding the mechanisms leading to behavioral and ecological variation within a species will therefore depend upon documenting this variation in both males and females, a conclusion that is hardly surprising. It is disappointing that research on fundamental aspects of the biology of even organisms as well-studied as Anolis lizards remains largely focused on males

There are reasonable reasons for focussing research on males. Male anoles are indeed often easier to spot in the field, and are certainly easier to catch. And incorporating an effect of sex into our statisical models will require us to double our sample sizes. But in many species, observing and catching females isn’t so difficult as to excuse not studying them. For example, in the last month or so, my undergraduate collaborator Rachel Moon and field assistant Barbara Da Silva have measured the ecology and morphology of over 300 Anolis sagrei females—an enviable sample size in any circumstances.

Females have been ignored in all sorts of studies of all sorts of organisms. The absence of female subjects in biomedical trials, for instance, has far more serious consequences than the gaps in our knowledge of the biology of female anoles. Nonetheless, given that many of us are dedicating some portion of our lives to understanding these animals, making sure that we don’t ignore half of them seems like a worthwhile goal. IMG_3060

*This gap exists for two reasons: some previous studies don’t sample females, others sample both sexes but don’t distinguish between them.

6 thoughts on “Movement Rates in Anolis carolinensis Redux (Or) We Need to Study Female Anoles!

  1. Glad my wife doesn’t read this site. She would explode with, “Yea, once again women being ignored!”

  2. Very interesting post!

    I would also add that, as with most lizards, perhaps another reason females tend to be ‘ignored’ is that there is still very scant evidence for female choice in anoles. In a taxa studied by evolutionary ecologists, where sexual selection is a major topic of interest, this often leads to people thinking that females are unimportant in driving patterns of divergence and phenotypic variation. When you look at fish and birds, which often show strong female choice, females are heavily studied.

  3. I find this reason rather unsatisfying. First, post-copulatory sexual selection, including sperm choice, has been documented quite a bit in lizards, which ought to restore the importance in biologists’ minds of females in driving divergence and variation.

    But step back for a second. Why is the only divergence and variation we’re interested in that of males? Yes, males are often showier, both morphologically and behaviourally, but until we actually examine what variation looks like in females, how will we know that there’s nothing interesting there to look at? Take the female dewlap in anoles, for example, which shows extensive variation that wasn’t really studied until just a few years ago (http://www.anoleannals.org/2012/05/31/female-dewlaps/). Or intrasexual aggressive encounters in female anoles, which definitely occur, but to which scant attention has been paid. And the absence of female choice is not relevant to many ecological traits, but these traits still get studied more in males than females.

    I don’t mean to point fingers–individual researchers have millions of reasons for deciding to sample in the way that they do, many of which don’t make it into the paper they write. But as a community of researchers studying a single group of organisms, I think we can do better.

  4. Last year Ellee Cook began her project on female territoriality, which should begin to fill the gap in our current understanding of the ecology and behavior of female anoles and potentially to shed some light on territoriality; she is currently in the field for a second year of data.

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