Category: Natural History Observations Page 10 of 34

Anolis gundlachi. Photo by Alejandro Sanchez.

Anolis gundlachi 10 seconds later. Photo by Alejandro Sanchez.

West Indian photographer and natural historian extraordinaire Father Alejandro Sanchez sent in these photos, commenting “I took these two pics less than 10 seconds apart from each other – the time it took for me to modify the flash’s settings. Yet the lizard noticeably changed color patters in such a short time, surely for being scared by my proximity. Anolis gundlachi is one of my favorites.”

And note those blue eyes!

Broken Caribbean termite nest.  These termites may infect anoles with a thorny-headed worm parasite, Oncicola venezualensis.

Among the many anole parasites are the acanthocephalans, or thorny-headed worms, which in anoles are typically found as encysted larvae in the body cavity, muscle, or under the skin. One of these acanthocephalans – Oncicola venezualensis – is relatively common in anoles on the Puerto Rican Bank, and is the main character in one of my favorite anole-parasite stories. The story has three parts: 1) how the parasite gets into anoles, 2) how it continues its life cycle beyond anoles, and 3) the mystery of when it all began.

In addition to anoles, O. venezualensis larvae occur in the Caribbean termites Nasutitermes acajutlae on the Puerto Rican Bank, which is a partially submerged landmass comprised of Puerto Rico and all the Spanish, U.S., and British Virgin Islands except St. Croix. These termites construct protective nests and foraging tubes in which they live (see photo), and each individual termite belongs to a morphologically distinct caste. Most are in either the soldier or worker caste, and soldiers are larger than workers, aggressive, and armed with big mandibles. These two castes also have slight color differences – worker termites have yellow heads, whereas soldier termites have dark yellow heads.

Anoles eat termites, and O. venezualensis manipulates both the behavior and appearance of its termite hosts in order to increase the likelihood that the parasitized individuals will be preyed on by anoles (Fuller et al. 2003). Infected termites behave carelessly when compared to their uninfected peers. When a foraging tube is broken, for example, the parasitized workers arrive quickly and then linger, a behavior that makes them more susceptible to predation by anoles. Infected termites also look different, as the head color of infected workers changes to a pale yellow. This increases the difference in appearance between the parasitized workers and the aggressive soldiers, and anoles presumably try to avoid eating soldiers (remember that anoles are smart decision-makers!). The color-changing strategy is effective – in feeding trials with Anolis cristatellus where the lizards were presented with petri dishes containing both parasitized and parasite-free workers, the lizards consistently preferred the light-colored parasitized termites.

After the anole ingests a termite infected with O. venezualensis, the parasite encysts (i.e., forms a cytacanth) somewhere outside of the host’s gastrointestinal tract. In anoles it remains in its larval form, unable to complete its life cycle, and waits for the lizard to be ingested by its definitive host where it will mature into an adult and undergo sexual reproduction. The identity of O. venezualensis‘s definitive host remained elusive for some time. Two primary suspects were mongooses and the pearly-eyed thrashers, since both eat anoles and are common on the Puerto Rican Bank. But, O. venezualensis remains in its larval form in both of these hosts (Nickol et al. 2006). The mystery was solved a couple of years ago – it’s cats! Fuller and Nickol (2011) necropsied a feral cat on St. John and found 87 adult worms. The life cycle for O. venezualensis is now understood to be termite → lizard or bird → cat, then begins again when termites ingest parasite eggs in cat feces. The mongooses aren’t eaten by cats, and so are dead-end hosts for the parasites.

For me, learning that the cat is the definitive host was a head-scratcher. We know that cats eat anoles, and feral cats are abundant on the Virgin Islands, particularly St. Thomas. But, it’s hard to imagine how a parasite with a complex life cycle of at least three hosts (termites, anoles/birds, cats) became invasive across so many islands. It’s also possible that a different, native anole-eater also serves as the definitive host. Bats are the only extant native mammal species on the Virgin Islands, and we know that some bat species eat anoles. Perhaps bats are the original definitive hosts? In any case, the populations of O. venezualensis have likely increased in recent times due to the introduction of cats on those islands, and whether that’s had any effect on the anole populations is unknown.

Photo by David Herasimtschuk

David Herasimtschuk took this striking photo along the Rio Carbon near the town of Bribri in Costa Rica. Here’s what happened: “The story of how I photographed this image was very bizarre. I was working my way up a stream with the intent to film poison frogs along the bank, and I saw the blue morpho floating down the stream. It was fluttering and still alive, but was being harassed by a school of very hungry fish. Feeling sorry for the animal and curious to see a blue morpho up close I pulled it out of the water. At that point it wasn’t doing to well, but I felt bad throwing it back in the stream, so I placed it on a branch thinking if it might be able to rest and dry off. I then left to film frogs, and came back about a half an hour later. When I returned the butterfly was gone.  Initially I thought it had survived and flew off, but then I saw a bright blue shape in the mouth of stream anole a couple feet from where I had placed it. It was a strange set of events, and it definitely reinforced my belief that when you live in a tropical forest everything wants to eat you.”

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.

Anolis stratulus

Anolis evermanni

Anolis gundlachi

Ok, this post has nothing to do with Frank Sinatra other than his nickname. But what about blue eyes in anoles? They seem to pop up all over anole phylogeny. For example, in my recent trip to Puerto Rico, three anoles had cerulean peepers–A. evermanni and A. stratulus, which are closely related, and A. gundlachi, which is more phylogenetically distant. And blue eyes occur in other anoles, such as A. etheridgei from Hispaniola.

The observation raises two questions:

1) Just how phylogenetically widespread is the occurrence of blue eyes in anoles? I know I’ve noted blue-eyedness from time to time, but I haven’t get tracked and can’t remember in which species. I propose the Anole Annals community take it upon itself to compile a list of blue-eyed anoles. If you know of one, please post a comment and, even better, add a photo.

2) Why? I can’t believe there is an adaptive significance to having blue eyes per se. Is it genetically linked to some other adaptive trait? Could sexual selection have a role (though I don’t know of sexual dichromatism in eye color)? Other animals exhibit interspecific variation in eye color and I bet there’s a literature trying to explain it, but I’m not familiar with it. Would make an interesting project!

Some quick googling reminded me of a few other examples, below. Who am I missing? And does anyone have a good photo of blue-eyed etheridgei?

Anolis transversalis

Anolis peraccae

Anolis oculatus