For the past eight years, my lab has conducted intensive research on green anoles (Anolis carolinensis) in Palmetto State Park in Luling, Texas, about an hour east of San Antonio. This park is beautiful – it’s centered around a swampy area dominated by dwarf palmettos (Sabal minor), and the San Marcos River flows through it. We’ve marked lizards and mapped their home ranges, watched their behavior, measured their morphology and parasite loads, and so much more. In past years, we’ve calculated that the density of green anoles in the park is approximately 0.04 lizards/m2, or about four adult lizards in every 10m x 10m area. We could regularly get sample sizes of around 150 lizards for behavioral studies in the park, but we very rarely collected animals from the park – we left them where we found them!
But this year is different. On three field trips to the park this summer, we have found very few green anoles. On our first visit this year in May, we spent 16 person-hours searching for lizards and found four green anoles. On our second visit in early June, we spent 14 person-hours searching and found eight. Last week, we spent another 12 person-hours and found only two. We see green anoles all over the city of San Antonio, and the students in my team are all skilled lizard spotters and catchers, so this isn’t due to inexperience. Also, we see other species of lizards all over the park – most commonly, Texas spiny lizards, little brown skinks, and house geckos– as well as garter snakes, copperheads, and cottonmouths. We also see tons of frogs.
Garter snake eating a tree frog, at Palmetto State Park. Other herps are thriving there!
So what happened to the anoles? We’ve considered a number of possibilities. The first thing we thought of was the possibility of feral cats – but we haven’t seen any cats in the park, and we think cats should have the same effect on the other herp species. What if the insect population had crashed? But again, that would affect the other lizards, snakes, and frogs too. This isn’t a year of particular drought or excess rain (and in previous wet and dry years, we’ve still seen lots of anoles), and the vegetation throughout the park largely looks the same as it has in the past. Perhaps an anole-specific disease has spread through this population?
In any case, the paucity of anoles in the park this year suggests that there won’t be many next year either, as there’s almost no one around laying eggs. It’s a bummer, because we’ve had such success here in the past.
Any ideas to explain this, AA readers?
Work we’ve published from our previous research in Palmetto State Park:
- Dill, A.K., T.J. Sanger, A.C. Battles and M.A. Johnson. 2013. Sexual dimorphisms in habitat-specific morphology and behavior in the green anole lizard. Journal of Zoology 290: 135-142.
- Battles, A.C., T.K. Whittle, C.M. Stehle, and M.A. Johnson. 2013. Effects of human land use on prey availability and body condition in the green anole lizard, Anolis carolinensis. Herpetological Conservation and Biology 8: 16-26.
- Bush, J.M., M.M. Quinn, E.C. Balreira, and M.A. Johnson. 2016. How do lizards determine dominance? Applying ranking algorithms to animal social behavior. Animal Behaviour 118: 65-74.
- Stehle, C.M., A.C. Battles, M.N. Sparks, and M.A. Johnson. In revision. Prey availability affects territory size, but not territorial display behavior, in green anole lizards. Acta Oecologica.
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Tracy Langkilde
Have fire ants moved into the park recently? They’ve been in that general area for a while. From preliminary studies of interactions, they appear to have a bigger impact on lizards than snakes or many frogs.
Aaron C. Joyce
We’ve been experiencing the green anole decline here in South Florida for quite some time. We seemingly can attribute that to habitat loss, pesticide distribution and many other man-made intrusions like invasive species. Those who know how to find them can still go find them in secluded wooded areas away from Main sources of agriculture or habitat destruction. Seemingly they do still Thrive but only in one hundred percent natural areas. As a child in these natural areas I used to find much more though, the lack of, I would attribute to pesticide spraying, bugs that they are spray for seem not to be obsessed with a certain area and we’re given wings to fly away from those wooded areas where the anoles are. Pesticides can not only kill bugs, but if they survive, those bugs can introduce weakened genes into the environment.
Rebecca
My anoles have vanished too!!!! I am bummed cause I love them….Dallas area
AJ Watkins
I am in Galveston Texas, and I am literally in tears. Being a Port city, we have been invaded by the Cuban anoles that have obviously come in off the shipping boats. All I can say is they have caused complete devastation to SO MANY native species here on the island. Where once I had assassin bugs calore in my yard, as I never use pesticides, I also hardly ever had any issues with plant pest bugs, as the assassin bugs ( I called them my garden army) would take care of the aphids, white flies, mealy bugs, etc. Now, since the invasion ( and I do mean INVASION) of the Cuban brown anoles, they have decimated the assassin bug population. I haven’t seen a single assassin bug for at least 3 years now. They also eat all the Pipevine Swallowtail Caterpillars, the Monarch caterpillars, and the Giant Swallowtail Caterpillars. They do kill and eat all the baby green anoles, the green anole eggs, and will outcompetes and fight with the larger Green anole males. As of this year, my back yard is over run with Cuban anoles, and I am talking HUNDREDS of them. I try to keep the Cuban anoles away from my front porch area, as I did have 3 green anoles that hung out on the plants on my front porch. That was earlier this summer. Since then, I had one baby green anole hatch out, but then disappeared ( she was SO TINY) I am assuming she got eaten by a Cuban anole. In the past couple of weeks, the one large green anole male I had, has disappeared, as well as the adult female I had hanging out up here on my porch too. At this point, I only have one juvenile green anole left, which I painstakingly try to help along by catching flies and feeding them to her ( I am assuming a female). The Cuban anoles are so much faster, and they eat EVERYTHING, so all my green anoles were looking very skinny, but I was trying to help them ( the green anoles) all out by providing extra food for them. The juvenile I have left, has become very friendly with me, and will sit out here on my handrail with me as long as I am present. I think it knows that I will run off the Cuban anoles if they try to come up here, so she feels safe as long as I am around. When I go inside, though, she disappears and goes to her hiding place (which I don’t know where that is). The Cuban anoles have completely disrupted the balance of things in my yard and garden, and I have even try to do some “population control”. Invasive species, whether animal or plant, always outcompete native species. TPWD encourages the control of non-native species, so that is what I am trying to do, but at this point, I think it is too late, and the City of Galveston has done nothing about it. I am so disappointed and disheartened. Where once I had a thriving garden with butterflies that grew out from caterpillars, tree frogs, house geckos, and so many other beautiful native species in my back yard, now all I see are Cuban anoles EVERYWHERE. I rarely see a house gecko, and there are no more frogs. I do have a few Gulf Coast toads, but that is it. The Pipevine swallowtails still lay their eggs, but the Cuban anoles eat all the eggs before they get a chance to hatch. I don’t even plant milkweed anymore. What’s the point??!!! The Cuban anoles just eat the eggs or kill and eat the few caterpillars that make it long enough to hatch out of the eggs. Where green anoles only lay 1 egg at a time, Cuban anoles lay several at a time. I have never seen such a devastating species of animal in all my life. It makes gardening on this island much less enjoyable, and I literally despise these Cuban anoles. I love nature, and would never kill any living thing in my yard… Until now. So if you are noticing a decline of green anoles in your area, you might want to start watching for Cuban anoles. I know they have made it to Houston, as I have seen posts from Houston gardners complaining about them as well. They are always brown, or even black colored, never green. Females have a cream colored stripe down their back, with black lines on either side of the cream stripe. The males have a checkered like pattern on them. They have a smaller head, stubby like head, and they are super fast. I know the grackles catch lizards in the spring to provide protein for their hatchling babies, but I don’t even think the grackles can catch the Cuban anoles. They are just too fast for them to catch them. The only advice I can give, is if you do start to seeing them in your yard, start swatting them HARD with a very heavy duty fly swatter… If you can catch up to them. Look up the pictures though, and make sure you aren’t mistaking a green anole for the Cuban anoles. Female green anoles can have a white or cream stripe down their back too, and turn a tannish brown color more than the male green anoles do. Make sure you aren’t killing green anoles. I hate to say it, but I think the days are numbered for our native green anoles (as I said, all but 1 are gone out of my yard) , unless we can figure out a way to control the Cuban anole population, but not harm the green anoles. I think that feat is impossible though. 😢