We need YOUR help to solve a lizard mystery!
For the past eight years, members of our Lizard Lab have studied green anole lizards (scientific name: Anolis carolinensis) in Palmetto State Park in Luling, Texas. This park is about an hour east of San Antonio (where we live), and it’s a beautiful place. The park is named for the many dwarf palmetto plants in the swampy center of the park, and the San Marcos River flows through the park too. In our work in the park, we’ve watched lizard behavior, mapped where they live, measured their body size, and counted the parasites that live on them. We calculated that the density of green anoles in the park (or, how many lizards live in a small space) is approximately 0.04 lizards/m2. This is the same as four adult lizards in every 10m x 10m area, or one lizard in a space about as big as two rooms of your house. While we’ve studied these lizards a lot, we don’t catch the lizards and take them out of the park – we leave them where we find them!
But this year is different. We’ve been to the park three times this summer, but we haven’t found very many green anoles. We do see many green anoles in the city of San Antonio, and we are very good at seeing and catching those lizards. Also, we see other species of lizards all over the park – most commonly, Texas spiny lizards and little brown skinks – as well as garter snakes, copperheads, and cottonmouths. We also see tons of frogs. (Check out the photo below to see a garter snake eating a tree frog. Other reptiles are doing great in the park!)
So what happened to the anoles? We don’t know, but we’ve been thinking about it and talking with other scientists who study lizards, and with the staff who work in the park every day. The first thing we thought of was that maybe there were cats in the park – cats kill lizards, and can wipe out a whole lizard population quickly, but we haven’t seen any cats in the park. What if the insects that the lizards eat have all died? If that happened, the other lizards, snakes, and frogs would die too, not just the green anoles we’re looking for. Weather can also affect lizards, but this isn’t a very wet or dry year, and it didn’t get too cold last winter for the lizards. And, the plants in the park look the same as they have before.
The best ideas we’ve come up with, are that maybe a disease that only affects anoles has spread through this population, but that seems very unlikely. Or, maybe some other people caught all the lizards they could find in the park, to sell them. This is against the law, because you’re not allowed to take animals or plants out of a state park without permission.
Do you have any other ideas to explain this, lizardsandfriends readers?
The Lizard Lab team at Palmetto State Park, May 2017.
Note: another version of this post was originally posted on anoleannals.org on July 6, 2017.