Anolis is the most species rich genus of lizards, with nearly four hundred described species in the tropics of the New World (and probably many more yet to be named). Yet, of all the anoles great and small, near and far, green and brown, one stands out for its combination of elegance, charm, and mystique. I refer, of course, to the Ecuadorian horned anole, Anolis proboscis, denizen of Andean forests, possessor of an enchanted sword, and all-around lizard of mystery. Now, however, the veil has been lifted, as the first reports on the biology of the previously unknown lizard have just been published in Breviora, a journal of the Museum of Comparative Zoology at Harvard.
The mystery comes in three acts. The first concerned the continued existence of the horned anole. The species was discovered in 1953 and over the next 13 years, another five were found, all male like the first, all from the vicinity of the Ecuadorian town of Mindo. Then, for four decades…nothing. Many feared the species extinct, perhaps a victim of the deforestation that has ravaged so much of the Western side of the Andes. All this changed in 2005 when a group of birdwatchers spied one crossing a road near Mindo (mind you, this is an arboreal lizard—insert your own joke). Anolis proboscis lives!
The photo above made its way onto the internet and to the attention of Steve Poe, an expert on locating hard-to-find anoles, who led a team of American and Ecuadorian scientists back to Mindo in the summer of 2009. Poe’s approach to finding day-active anoles is seemingly perverse: he stays up all night looking for them. The reason is simple: many anole species sleep on narrow twigs or leaves, presumably because approaching predators will produce vibrations on the flimsy perches, alerting the lizards to impending danger. Although this strategy may be effective in avoiding predators that creep, crawl or slither along branches, it’s not so well-suited to avoid detection by flashlight-toting herpetologists, who are attuned to locating the tiny reptiles—which conveniently blanch to a pale color at night—even when they’re roosting 20-30 feet high in the canopy. Poe’s team quickly located a large number of lizards, establishing that the species not only exists, but seems to have a healthy population.
Unbeknownst to Poe, another team of researchers independently had discovered a new horned anole population. This team, from the Ecuadorian Museum of Science in Quito, located five specimens of the horned anole at two sites 11-13 km northeast of the original collecting locality, slightly extending the known range of the species. Both groups published detailed descriptions of the anatomy of the species—the Ecuadorian group last year and Poe’s team as the first of the Breviora set published today—describing previously unknown variation in horn size and shape, as well as differences in color and patterning both among males and between the sexes.
And, speaking of differences between the sexes, that leads to the resolution of mystery number two. Ever since the species was first described and the initial half dozen specimens collected, lizard enthusiasts have wondered—what about the females? Do they have horns, too? Of course, in the absence of any information on the natural history of the species, it was hard to have an informed opinion. Is the horn used in self defense, in which case the lady lizards could probably use one as well as the guys? Or is it used by males to fight amongst themselves, or even as an ornament used to woo or titillate? Nobody knew, and so it was anybody’s guess whether the females were nasally adorned or not. But now we know the answer. Before I reveal it, take a moment and take a guess: yes or no? When you’re ready, scroll past the lovely photo of another male and see for yourself.
No horn on the female! That would seem to suggest that the horn is involved in sexual selection, either competition among males for females or mates, or female choice of males.
And, finally, that leads us to Mystery #3, one that has yet to be fully resolved. Namely, what is the life story of this species? Where in the habitat does it live? What does it do? And, of course, the horn—what’s going on with that? Poe’s group found lots of lizards, but only at night. They provided information on the bedroom ecology of the species, but that’s about all, save a few observations detailed below. The Ecuadorian group provided only a smattering of information: two females were found during the day in small bushes. In other words, very little was known about the natural history of this species.
For that reason, I led a group of American, Ecuadorian, and Belgian scientists back to Mindo in the summer of 2010. Our goal: find the horned anole during the day and collect data on how they live their lives. This proved harder than expected. We would go out in the night and light them up with our flashlights, but when we went back to the same spots during the day, nada—no lizards to be seen. In desperation, taking a page from detective stories, we set up a stake-out: we found the lizards at night and then returned before dawn, planning to follow them as they woke and went about their business. What we didn’t realize, however, is that even on the equator (Mindo’s latitude is 0 degrees, 3 minutes South), it can be very cold at 4500 feet elevation just before dawn. And we also didn’t know that we were standing in a valley between two mountains, so that even though it became light at 6 a.m., the sun didn’t actually strike us, or the lizards, until 9 a.m. The lizards, sensibly, slept in and waited for the warming rays to find them. Meanwhile, we shivered.
But eventually the lizards did awaken, and we were able to follow them around for anywhere from a few minutes to several hours. Ultimately, from evening stake-outs and the fortuitous discovery of a few individuals during the day, we learned a great deal about their behavior and ecology. And it became obvious why they went undetected for 40 years and are so rarely seen. The reason: they live an extraordinarily cryptic lifestyle, moving extremely slowly, creeping along, step-by-step, never proceeding at a pace that could be categorized as anything faster than a crawl. Add to that the fact they are incredibly well camouflaged in the thick yellow and green vegetation in which they occur, and that they usually occur high off the ground, and it’s no wonder few people ever see them. Indeed, when we showed some to locals in Mindo, most said they had never seen one before.
Our observations confirmed one hypothesis. Slender, cryptic, with short legs and tail, the horned anole looks all the world like Caribbean Anolis species that are specialized for living on narrow surfaces. Our observations on behavior and habitat use confirmed that the horned anole has evolutionarily converged on the twig anole lifestyle, which itself has evolved independently on each island of the Greater Antilles (Cuba, Hispaniola, Jamaica, and Puerto).
Except, of course, that the horned anole has a horn, unlike its island-living brethren. Unfortunately, we saw no male-female interactions, and only brief male-male encounters, but photographer James Christensen, a co-author on the Poe et al. paper, did observe one mating event, in which the male “flourished” his horn from side-to-side as it approached the female. In addition, when two males were put together on a branch, the dominant one lightly touched the other, which shortly thereafter ran away.
Although these observations provide only the slightest hint of the horn’s role, we did make two discoveries. First, I had envisioned sword-fighting among males, just as many other animals with horns or antlers contest to establish dominance. However, we were quickly disabused of this notion when we caught a male and placed it in a plastic bag. When it bumped into wall of the bag, the horn folded over. Subsequently, we saw the horn bend upon contact with leaves or any other object (see a video here)—it has no stiffness whatsoever. Clearly, there is no fencing with these sabers.
Second, we noticed that some males had droopy horns, whereas those of others were angled upwards. What we didn’t realize is that horn shape is not immutable. Rather, males are able to move their horns at will, and do so immediately before eating, raising the horn out of the way (video here). This was a shock; the horn is attached to the tip of the snout, where there shouldn’t be any muscles. Perhaps hydrostatic pressure is used to change the horn’s shape, just like another organ with which everyone is familiar, but at this point, we don’t know.
So, the horned anole of Ecuador is less enigmatic, but its horn—what it uses it for, why it evolved, how it moves it—remains a mystery. Our Ecuadorian colleagues continue to collect data and have even bred them in the lab. And, fortunately for the lizards, the town of Mindo has become a destination for ecotourists, and as a result, the forest is being preserved, and with it, these wonderfully fascinating little lizards. Long live the horned anole of Ecuador!
For more on anoles, check out the Anole Annals.