Anole Annals

The best anole fossils have been found in amber [e.g. 1,2]. Amber is, of course, fossilized tree resin, and I have often wondered how likely it would be that a lizard would manage to get itself stuck in tree resin. After all, as we know from catching them, small lizards are nothing if not agile.

Sitana ponticeriana is a small agamid lizard found in dry habitats across South Asia. Though most commonly found in disturbed, open habitats, they also occur in the rapidly dwindling stands of thorn scrub forest found across India.These forests are dominated by resin-producing Acacias, and are being invaded by the resin-producing Prosopis juliflora.

Acacia forest in Kutch, India

This sort of forest is exactly where you might expect to find lizards interacting with resin, and here is an example. This female Sitana ponticeriana, caught in the forest shown above, had a finger on her front foot completely stuck in a little ball of resin. It is easy to imagine how a slightly smaller lizard or a slightly larger piece of resin could result in an inextricable lizard and, in several thousand years, a very cool fossil!

Female Sitana ponticeriana with resin stuck to her toe

[June 12 2012; 8:35 a.m.]. During a placid morning, a team from Herbios Group Panama observed an impressive image. We witnessed an Oxybelis aeneus (147 cm, 55 g) with an Anolis lionotus male (22.9 g) caught in her jaws. He was the breakfast meanwhile, his fellow female just observed the scene.

We were so happy to witness such an event, thinking about what was the male doing while the predator took the chance. Perhaps He was displaying to attract the cryptic female, or just was distracted while feeding! In any case the snake had the morning meal and the male paid the price.

Avid readers of this blog might have noticed that Jonathan Losos likes trying to get readers to confuse the white-fanned variant of the South Asian agamid lizard Sitana ponticeriana with the only toepad-less anole, Anolis onca. Indeed, the two lizards look quite similar:

Sitana ponticeriana, white-fanned variant, in Saswad, India

Anolis onca in Maracaibo, Venezuela. Photo by Jonathan Losos

Posts [1, 2, 3] detailing the habits and habitats of these two lizards point to a number of similarities between the species. Both occur in incredibly hot and windy environments. Both are primarily terrestrial, where they are very well-camouflaged, but are also observed perching on vegetation. The causes for the loss of A. onca’s toepads remain a mystery, and here I lay out some observations of S. ponticeriana’s behaviour that lead to a hypothesis for why A. onca might have lost it’s toepads.

Perch use in S. ponticeriana follows a predictable temporal pattern from about 8:00 a.m., when the lizards first emerge, to about 12:00 noon, the hottest part of the morning. Lizards perch primarily on rocks, if available, in the early morning while basking. During the middle of the morning, male lizards are found perching on and displaying from a variety of perches, including the ground, mud piles, rocks, twigs, and shrubs. By noon, however, lizards are often found resting in shrubs. Here are a couple of lizards resting:

Male Sitana ponticeriana, white-fanned variant, resting in the shrubs. Saswad, India.

Female Sitana ponticeriana, white-fanned variant, resting in the shrubs. Kutch, India.

But what happens when you chase lizards out of the shrubs in the heat of the day? Peak air temperatures at the site I was at this summer hovered around 40 degrees Celsius, and soil or rock surface temperatures were likely higher (they certainly felt so). Lizards that we chased out of shrubs onto the sand would run rapidly as usual, but when they paused, were often observed lifting the toes of their hind feet off the ground. Here are two photos–compare the toe positions on the hind foot to get a sense of the behaviour I’m referring to:

If the highest risk of heat exposure comes from the ground, any adaptation that reduces the transfer of heat from the ground to the lizard will be favoured. Such adaptation would explain S. ponticeriana’s behaviour of resting in vegetation during the hottest part of the day and lifting toes off the ground when forced onto hot terrestrial perches. Like most agamids, Sitana have very skinny toes, leaving a small surface area for transfer of heat from the ground. But what about A. onca? If the ancestral A. onca had typically anole-like toepads on moving to the beaches, they might have been at high risk of heat transfer from the sand when forced onto terrestrial perches in the heat of the day. This would lead to the evolution of reduced toepads to avoid such heat transfer. A temporal pattern of perch use in A. onca, similar to that of S. ponticeriana, would be the first piece of evidence useful for establishing what might be an exciting example of trans-continental convergence.

If I were a brown anole, I’d take offense at a flag like this, too!

Pat Shipman from the AA Little Cayman Bureau checks in:

The observation that anoles nod at inanimate objects (or possibly at anoles the observer hasn’t spotted) is not new.

A few days ago, I watched an adult male sagrei repeatedly unfurling his dewlap and displaying… at an orange landscaping flag that marks the location of a large septic pipe underground.  What was most interesting is that the flag was fluttering in the breeze and that it was a shade of orange almost exactly the same as the sagrei’s dewlap. Alas, I did not have a camera handy to record this event.

Has anyone else noticed sagreis paying special attention to orange objects?

According to Williams and Rivero, the name occultus was chosen for the anole they described in 1965 because it means “hidden,” referring to the unexpected finding of a new species in such a well-trodden spot (“The discovery of so distinct a species in an island thought to be well known herpetologically and in which the anoles have received special  attention must give us pause.”). But to the unknowledgeable, “occultus” sounds more mysterious, more preternatural, befitting such a spectral, gnome-like species that is so rarely seen and so little known.

On a recent trip to western Puerto Rico, I was fortunate to visit a locality where they can be found readily at night. In a short evening, we found five clinging to the ends of twigs (as well as a dozen green giants). Naively, I thought that I’d come back during the day and locate some to see where they live when they’re active, and what they do. Ha! Much, much easier said than done. How do you find a little, camouflaged gray match-stick of a lizard in the dense vegetational matrix that is a tropical forest? The answer: you don’t, and I didn’t.

I’m thirsty! Photo by J. Losos. For more on drinking occultus, check out Manuel Leal’s recent post on Chipojolab.

Indeed, there are almost no data on the natural history of this species, except where it sleeps. The little that we do know suggests that they are just what they look like–twig anoles. Some of the few that have been found have been on twigs, though a surprising several have been on leaves or ferns. They seem to creep slowly, though no one has published a good behavioral description.

Photo by J. Losos

Since the description of this species in 1965, there has only been one paper written on the diurnal natural history of this species, published by Preston Webster in 1969–44 years ago (go ahead, read it yourself)! Someone needs to go out and find these guys and see what they do! How to do it? Go find them at night and come back before dawn and watch them as they wake up and get out of bed. And here’s a bonus–George Gorman published a paper suggesting they sleep in pairs–that’s right, pair-bonding twig anoles!

Note that these photos were taken of animals captured and placed on twigs, as was the lizard which subsequently started drinking raindrops discussed on Chipojolab.

And here’s one acting like a real twig anole. Photo by J. Losos.