Curly tail with brown anole tail visible from its mouth
Kayaking to cays
I was recently in Abaco, Bahamas with Losos lab post-doc Oriol LaPiedra and Ph.D. candidate Darío Fernández-Bellon from University College Cork, Ireland, to carry out some behavioral studies of Anolis sagrei on the island and its surrounding small cays. We kayaked (a highly recommended transportation mean for its lesser-impact on the marine ecosystem, not having to rely on the tide schedule, while allowing you to see rays and sharks and sea turtles!) our way out to islands that are known to have A. sagrei naturally existing alone, or with one of their natural predators, Leiocephalus carinatus.
Curly-tailed lizards are known to prey on A. sagrei and can have significant impact on anole behavior and adaptation. Twice I observed Leiocephalus capturing and consuming A. sagrei, one of which was an adult male and the other an adult female. We have also noticed that the A. sagrei on these island tend to perch higher and are seldomly seen on rocks or leveled ground compared to those on islands without curly tails, so this behavior could be an effect of Leiocephalus being present.
A female red-winged blackbird with a A. sagrei in its beak
On a different island where Leiocephalus were absent, A. sagrei are still under predation pressure, this time by red-winged blackbirds nesting on the island. We observed a female blackbird with an A. sagrei in its beak waiting for us to leave the island so that it can feed its chicks. This observation suggests that A. sagrei on islands without Leiocephalus might still be under predation pressure by other species that might not be present on the island at all times. Also, predation pressure exerted by an aerial predator differs from that by a terrestrial predator or if both predators are present, so this might be a factor in morphological or behavioral changes in these lizards on these islands.
Anolis sagrei on one of the small cays
Other interesting observations include A. sagrei density on islands seems to be unintuitive. Some small islands with fewer perches hosted many more adult males and females than large islands did. Sizes of individuals also seem to vary greatly between different islands: small cay A. sagrei seem to be, on average, larger than those on mainland Abaco. Personally, I am unable to note major differences between islands which might have resulted in these observations. I’m excited to see if the data we’ve collected will give more insight into these observations as well as other behavioral results that will come from this study!
Reptiles are often thought of as solitary and not social animals. However, all of us who study anoles know that Anolis are anything but solitary animals. Spend a few minutes observing an anole and you might see it dewlapping, doing push-ups, tail wagging, and fighting with other males or even other anoles species. James Stroud, a Ph.D. candidate from the Feeley lab @ Florida International University, presented on Saturday about the exploratory results of a new research method he and Robert Heathcote have started to construct social networks of A. sagrei and A. cristatellus in Miami, Florida. A. sagrei and A. cristatellus are similar in morphology and ecology and they wanted to learn how patterns of social interactions between these two species allow them to coexist outside of their native range.
Individual social behavior manifests itself collectively at the population level and interactions between populations (within and between species) might act as a basis for evolutionary processes. James and Robert tagged both male and female anoles in their study to track and recapture the animals in the future for a long term study. They measured the distance between every two anoles observed and inferred the strength of interaction as stronger if the anoles were closer to each other. Both species show a great web of interactions both within and between species. Some individuals are also much more “bold,” interacting with many males and females of either species, while others show fewer social interactions. These preliminary data are exciting since so little is known about Anolis social behavior. James also mentioned that they will be including additional data such as the types of interactions that will add great complexity and insight to this story.
Cells infected with P. floridense (left and right) vs. healthy cells (middle)
Brian Devlin, a graduate student from University of Central Florida, presented a poster on differential rates of malarial infection by Plasmodium floridense between two Anolis species in Central Florida. While both species exist in the area, A. sagrei is the more recent invader. Brian hypothesized that the infection rate would be higher in A. sagrei because A. carolinensis has coexisted with the parasite longer and might have developed some resistance to it.
Brian collected blood samples from both species and examined the cells under the microscopes to look for signs of malarial infection. He actually found that the infection rates of P. floridense were significantly greater in A. carolinensis. Infection rate also did not correlate with SVL, sex, presence of tail autonomy, date or locality of the lizard. However, there is a higher rate of infection in the warmer months (May-July) possibly due to the in increase rainfall resulting greater mosquito presence. From these results, Brian hypothesized that the lower malarial infection rates in A. sagrei might have helped the species to outcompete A. carolinensis and successfully establish in Florida.