Anole Hearing: Much to Learn

What's that I hear? Photo by Melissa Losos

We think of anoles as visually oriented animals, but they can hear as well. Very little work has investigated their hearing ability, much less how they respond to aural phenomena. In a recent study, Huang et al. reported that anoles alter their behavior depending on what they hear. In particular, they show that A. cristatellus in St. John, U.S. Virgin Islands, appear to display less after hearing the call of a predatory bird, a kestrel, compared to their response to a non-threatening granivore, the bananaquit. They also report that simulated ecotourists playing the sound of a camera shutter clicking lead to a decrease in display rate compared to controls or the faux tourists taking flash photos. They interpret this finding as indicating that the sound of SLR cameras clicking, but not their flashes, are interpreted as a threat by the anoles. These results are interesting, but cry out for more thorough study, especially given that data were collected by approaching lizards, watching them for 1-2 minutes, presenting the stimulus, and then recording behavior for another minute and comparing rates of behavior from before and after. Moreover, differences in behavior among treatments were only detected in the final 15 seconds of the post-stimulus observation period, where no differences were detected in the first 45 seconds. Bottom line: it would be very interesting to investigate the role of hearing in anole behavior, and this study provides an inkling that there may be interesting work to be done.

About Jonathan Losos

Author and Professor at Harvard University
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1 Response to Anole Hearing: Much to Learn

  1. chipojolab says:

    Jonathan’s post brings back old memories and made me search my drawer of unpublished data.

    I don’t want to spoil the party, but before you go running to investigate the ability of anoles to respond to the calls of birds, I want to share my two cents. When I was a graduate student, I had the “great” idea that Puerto Rican anoles were responding to the call of one of their main avian predators “El Pájaro Bobo Mayor,” the Puerto Rican Lizard-Cuckoo (Coccyzus vieilloti). At the time, I had spent a considerable amount of time in the field working with herps, and I had made the observation that, in many instances in which I heard the distinctive call of the “Pájaro Bobo,” the anoles seemed to respond to those calls by fleeing. I convinced my advisor that this was a great opportunity to add a second modality to my research on signal evolution and got ready to work. I got a recording with two types of calls of the Pájaro Bobo and headed to field. My first stop was Bosque de Cambalache where both A. cristatellus and the Pájaro Bobo are extremely common. Many hours later, I came to the conclusion that A. cristatellus must just be an outlier. Basically, the anoles didn’t show any signs of responding to the call, but I was positive that others species would. Afterall I had witnessed their response many times before! Thus, I repeated the experiment, at EL Verde, with A. gundlachi … again, no response from the lizards. My “great idea” was a complete disaster, not a big surprise given my track record. Yet I was confused; I have witnessed anoles fleeing when I have heard the distinctive call of the Bobos many times before. Let me cut to chase, there is a small caveat to the story. In some of my trials, live Pájaro Bobos would come to the playback speaker, and as soon as the anoles saw the moving birds, they either froze or fled to the other side of the tree. This was the same behavior that I had previously noted when I heard the call of the birds. What did I learn from all of this, if anything? Do anoles hear the calls of the birds? Most likely yes. Do they care? NO. However, do the anoles detect the motion of the birds? Yes. Do they care? DOUBLE yes. I am positive that in the case of the Pájaro Bobo, what is happening is that although I only became aware of the presence of the bird by its call, the anoles were able to detect their motion (remember, these guys have great vision, including double fovea) way before I saw the bird. Thus they were responding to the motion of the birds, not to their calls, as I had wrongly interpreted from my original observations.

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