Invasive vs. invasive!

Studying anoles in South Florida means that I see interesting behaviors every day. For example, I had never seen a complete “courtship” sequence until a few days ago. I had seen many pairs of anoles mating, but I hadn’t observed the events that immediately preceded copulation. Mating can last several minutes, so it’s fairly easy to see, but the courtship sequence is much quicker.

I was getting ready to catch a small male crested anole (Anolis cristatellus) when a female approached from a nearby branch and jumped to the twig where the male was perched. He perked up and darted toward her. In a fraction of a second, he was holding her head securely in his jaws. His response looked so much like an aggressive encounter between males that I wondered whether I had misidentified the sex of the arriving “female.” But sure enough, the male then maneuvered his tail under hers and mated, her head still clamped firmly between his jaws. Did the female approach with the intent of mating, or did the male simply take advantage of the situation? Forced copulations occur in many animals, including Anolis, so perhaps that’s what I observed.

On my last day in Miami, I saw something even more unusual: an anole eating a snake! Yes, you read that correctly. Anoles often fall victim to snakes (especially Black Racers [Coluber constrictor], which are abundant where I work in Miami), but I’ve never heard of the tables being turned before. I was trying to capture some photos of my marked male anoles, so when I spotted an unmarked male in less-than-ideal light, I was prepared to move on. Then I noticed something long and thin hanging from the anole’s mouth. I directed my lens toward the anole, and as the image in my viewfinder came into focus I realized the anole was eating something worm-like, and this prey item was longer than the anole’s entire body!

Upon closer inspection, I saw a tiny mouth at the end of the “worm” – it wasn’t a worm at all, but a Brahminy Blind Snake (Ramphotyphlops braminus)! The blind snake is a tiny, fossorial (burrowing) snake that specializes in eating the larvae and pupae of ants and termites. Blind snakes are rarely seen above ground, so I’m not sure how the anole found its prey. But the blind snake, with no venom and tiny jaws specialized for small, helpless prey, was no match for the anole. It took a few minutes, but the anole managed to swallow the entire snake – a very impressive meal!

The photo I captured isn’t a work of art – the light was far from ideal – but it shows the unusual behavior. I love seeing new interactions between species, and in a place with as many invasive species as South Florida, such encounters are commonplace. Amazingly, every Brahminy Blind Snake ever collected, both in Florida and the snake’s native range in Africa and Asia, has been female. Female blind snakes can produce genetically identical female offspring without fertilization, a process called parthenogenesis. This unusual ability is probably part of what makes the blind snake such a good colonizer – only a single female needs to arrive in a new habitat to start a whole population!