I’ve recently learned that famous nature micro-photographer Piotr Naskrecki observed an aquatic anole catching prey underwater. Here’s what he had to say on his blog, The Smaller Majority:
The other aquatic iguana
In a couple of days I am heading off to the Galapagos Islands, where I hope to be able to see the incredible marine iguanas, the world’s only truly marine lizards. Other lizards enter water occasionally, but aquatic lifestyle is quite rare among these reptiles, and few species live and feed under water. But in rainforest streams of Central America there is one little known species of iguana that does just that.I first saw the aquatic iguana (Norops aquaticus) in the southern part of Costa Rica in 1994. These lizards swam and dove in a fast-flowing stream, catching water insects. But when I told a herpetologist friend about it, she refused to believe me.
It took me 13 years to find the aquatic iguana again, and this time I had a camera with me. It was in a different part of Costa Rica (Est. Pitilla in Guanacaste), but the animal and its habitat were the same. I watched it for a couple of hours, following the lizard among slippery boulders, hoping to document its hunting behavior. Eventually I got lucky, but alas, the actual catching of the prey happened underwater, when the iguana cornered a nymph of an aquatic blattodean (a yet undescribed species.) Next time I will definitely try to get a photo of the underwater action.
Update (2 Sept 12): Turns out that the aquatic Norops iguanas that I saw in southern Costa Rica and those from the northern part of the country, shown here, are different species. The animal in the photos is Norops oxylophus, not N. aquaticus. You can read more about the amazing aquatic behavior of N. oxylophus here. (Thanks to Annemare Rijnbeek for pointing me in the right direction regarding the ID of these animals.)
Incidentally, it appears that these lizards are once again being placed in the genus Anolis, where they historically belonged.
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Caribbean Anoles Function as Model Organisms for Evolutionary Dynamics
The small lizards adapted to unique niches among dozens of isles.
January 1, 2017|
It’s not easy to snare a lizard. Evolutionary biologist Michele Johnson affixes a noose made of dental floss to a telescopic fishing rod to reach into the bushes and tree canopies where Caribbean anoles live. By the end of the summer field season, her students from Trinity University in San Antonio, Texas, develop a knack for it. “We almost always catch our lizards,” says Johnson.
She doesn’t just collect field measurements and observations; she’s taken 30 different species of anoles back to her lab to analyze their physiology. Anoles have become a favorite model for evolutionary biologists because of their extraordinary diversity—there are more than 400 species in genus Anolis—and because of how they originally populated the Caribbean islands. The relative scarcity of mammals, snakes, or birds on the islands left many niches open for the lizards to occupy.
As anoles—which also inhabit Central and South America—reached individual islands, their populations diversified into island-specific forms that occupy certain niches. For example, each of the four largest islands in the Greater Antilles (Hispaniola, Cuba, Puerto Rico, and Jamaica) hosts one or more species that are green lizards hanging out in the lower canopies of trees, and another group of short-limbed, slow-moving reptiles that perch on twigs. These are two of the six “ecomorphs” that scientists who study Caribbean anole species have defined. To be considered an ecomorph, a set of habitat specialists must exist on more than one island, though the species in each group differ between islands. And yet, other anole species belong to no particular ecomorph class.
Caribbean anoles offer scientists a sort of “natural experiment,” explains Luke Mahler, an evolutionary biologist and herpetologist at the University of Toronto. Each isle, with similar environments, acts as a replicate for how anoles underwent convergent evolution into ecomorphs. As a result, evolutionary studies of anoles have flourished in the past couple of decades—think Darwin’s finches, but scalier.
“They really are a good model system for lots of questions, from very small-scale molecular work all the way up to adaptive radiation,” says Jerry Husak, a physiologist at the University of St. Thomas in St. Paul, Minnesota.
The basic anole ecomorphs go way back in evolutionary history, found Jonathan Losos, an evolutionary ecologist at Harvard University. Emma Sherratt, now at Australian National University in Canberra, got a hold of 20 fossil anoles while a postdoc in Losos’s lab. The fossils dated back 15 million to 20 million years, when the lizards were preserved in amber on the island of Hispaniola. Some were in museums, others in private collections. Using CT scans, the Losos team examined anatomy to confidently assign these fossils to four of today’s ecomorphs; a couple other fossils might be part of a fifth (PNAS, 112:9961-66, 2015). “At least several of the habitat specialist types already existed,” concludes Losos.
Despite the countless hours biologists have spent studying Caribbean anoles, the genus seems to have plenty of surprises still in store. In addition to her ongoing studies of physiology and behavior in diverse anole species, Johnson has recently focused on how her local Texan anole, Anolis carolinensis, determines dominance. A. carolinensis, like many other anole species, adopts a strict mating hierarchy in captivity, with males battling each other for access to prime habitat and to females. In the field, the hierarchy is more complicated—a lizard defending his own territory is more likely to win a fight, she thinks. She figured the biggest males would also be more likely to triumph, either in the lab or the field, and thus achieve larger territory and more females to court.
In order to correlate body characteristics and behaviors with dominance, Johnson’s group set up a sort of lizard fight club, pitting anoles against each other in one-on-one cage matches, with a single perch to battle over. Winners tended to execute more visual displays, performing push-ups and head-bobs and expanding the showy throat skin known as a dewlap. They also chased and bit the losers, who tended to back away and to hide in a corner.
But larger anoles weren’t always the winners in captivity or in the field. “Body size doesn’t predict who wins these fights at all,” says Johnson. Instead, behaviors made a huge difference—the most aggressive lizards won their matches. A longer head also helped, perhaps because it looked to opponents like a serious biting weapon. In the field, animals with a wider head and powerful jaws occupied larger territories with more females present (Anim Behav, 118:65-74, 2016).
Body size still probably matters, Johnson says. She has not yet tested in field studies whether size might help an A. carolinensis male establish his territory or take over a vacated area. And at least in other anole species, bigger males sire more offspring.
Mahler also got a surprise from the anoles when, in 2010, he received an email from Miguel Landestoy, a Dominican naturalist who claimed he’d seen a new species. Mahler was initially skeptical. “Everybody thinks they’ve got a new species,” he says, yet “the Caribbean anoles are the best known anoles, by a long shot.”
Then Mahler opened Landestoy’s pictures. “Holy crap,” he said. “That doesn’t look like anything we’ve seen on Hispaniola.” The critter was huge, by anole standards—about a foot from nose to tail tip. It had short legs, a short tail, and a mottled greenish-gray pattern that suggested it could easily blend into a mossy or lichen-covered branch. “I bought the first cheap flight I could find,” recalls Mahler.
The other thing that struck Mahler about the new species—which he and his colleagues dubbed A. landestoyi—was that it looked similar to anoles found in Cuba. Their clade is called chamaeleonides for their creeping, chameleon-like movements and camouflage prowess. These particular kinds of anoles, scientists had assumed, were unique to Cuba. But here was another species, making its living in many of the same ways, on Hispaniola (Am Nat, 188:357-64, 2016). “This is an example of what might be a seventh ecomorph. . . . Evolution is more predictable than we have yet given it credit for,” says Johnson, who was not involved in the project.
“It’s amazing, in part, that anything new there could be found after all these years,” adds Losos, a coauthor on the study. “The age of discovery is not yet over.”
As Skip Lazell showed nearly a half century ago, Anolis roquet on Martinique is extraordinarily variable in color across its range. This variation has been the subject of much recent work by Roger Thorpe’s lab.
Bermuda only has one native lizard, a skink. However, during the first half of the 20th century, three anole species were introduced. The first, the beautiful Anolis grahami from Jamaica, quickly spread over most of the archipelago, as David Wingate reported in 1965. However, Wingate noted that the subsequent two species, A. leachi from Antigua and A. extremus from Barbados achieved only more localized distributions.
Thirty-one years later, I published a follow-up survey. By that time, A. grahami had conquered the entire entire and A. leachi had greatly increased its range, but A. extremus was still limited to a far corner on the west end of Bermuda.
Joe Macedonia and colleagues have now returned for a 20-year follow-up, now 51 years after Wingate’s paper. In a paper just published in Herpetological Review, hey find that A. leachi is now also found throughout the Bermudian archipelago. Curiously, however, A. extremus has not advanced at all, with still a very small distribution in the west (see map below). The explanation doesn’t seem to be habitat availability, because there is no obvious difference between where A. extremus occurs and where it doesn’t. Macedonia et al. conclude, as I did, that it is competition from the very similar A. grahami that is preventing A. extremus from expanding its range.
Macedonia et al. also provide a wealth of information on the habitat use of all three species. And there’s a kicker–A. sagrei has recently been introduced to Bermuda. Will it expand its range and, if so, how quickly. Notably, A. sagrei is considerably more terrestrial than the other anoles on Bermuda, so the opportunity seems to exist.
We’ve had previous posts on the penchant of anoles to hitch a ride on a windshield, but this one’s the topper.
The truth must be told.
Previous work by Anthony Russell has demonstrated that geckos have a sophisticated vascular system and connective tissues that allows the toepad of geckos to be molded to the surface with great precision, enhancing the contact between the setal hairs on the pad and the surface. It had been speculated that a similar system existed in anoles, but no one had looked carefully. Now, Russell has, and he reports in Acta Zoologica that previous statements were mistaken: anoles lack what most pad-bearing geckos have. Here’s what the abstract says:
Adhesive toe pads of geckos house modified components of vascular and/or connective tissues that promote conformity of the setal fields with the locomotor substratum. Similar modifications have been claimed for the digits of Anolis, but evidence for them is not compelling. Angiographic and histological investigations of Anolis failed to identify any evidence of either an intralamellar vascular reticular network or a central sinus. Instead, their vascularity more closely resembles that of lizards in general than that of pad-bearing geckos. The loose connective tissue of the toe pads likely contributes to their general pliability and flexibility, promoting localized compliance with the substratum. Through the shedding cycle, the lamellae change shape as the replacing setae elongate. The outer epidermal generation lacunar cells on the inner lamellar faces simultaneously hypertrophy, providing for compatibility between overlapping lamellae, enabling reciprocity between them. This contributes to continuing compliance of the setal fields with the substratum. Overall, digital structure and attachment and release kinematics of the toe pads of Anolis are very similar to those of geckos exhibiting an incipient adhesive mechanism. Both lack major anatomical specializations for promoting conformity of the setae with the locomotor substratum beyond those of the seta-bearing portions of the epidermis.
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Karen Cusick, proprietor of Daffodil’s Photo Blog, watched this green anole turn from green to brown. Or mostly brown. I’ve seen this sometimes myself. Anyone know what’s going on here? Seen it in other green anoles?
Who says global warming is such a bad thing? Ok, it is, but at least there are some benefits, especially if you’re a brown anole in Florida. Read all about it in Daffodil’s Photo Blog.
The American Museum of Natural History just opened an exhibit on anoles that also presents information on the natural history and culture of Cuba. Or maybe it’s the other way around. But either way, you have to love their logo. The New York Times just reviewed the exhibit, and not surprisingly, anoles were a centerpiece of the article.
And here’s some text from the article:
From the recent ISBE Newsletter (28:2, p.26).
The artist, Ken Otter, who when not drawing is a professor at the University of Northern British Columbia, explains the back-story:
My first love was reptiles – birds came as a later incarnation (although I console myself that they are simply feathered reptiles). I was actually planning on shifting to working on anoles during my postdoc. I have had numerous ones as pets over the years – my students gave me a brown anole that became our lab mascot for about 5 years. I even had an undergrad student at the University of Nottingham that I was co-supervising with Pete McGregor run trials to see if males eavesdrop on dewlap displays of other males. Unfortunately, the student was primarily focused on nature photography, and we had a miscommunication on scientific design. I found out after the fact that he hadn’t quite followed protocol, so we couldn’t count all our trials, so the results were only ever presented in a conference poster and not published. He ended up as a photographer for BBC Wildlife though!
I had actually been awarded a short-term postdoc back in the 90s from the Association for the Study of Animal Behaviour to test anole signalling behaviour using video playback systems (very similar to the stuff that has since been done using Robo-lizards). Unfortunately, it came at the same time as I was offered a tenure track job here, and the University had a ‘northern research focus’ so wasn’t too keen on me heading off to the Caribbean to do field work. Guess now that I have full professorship I could always tell them to stuff themselves, but I have my research program set up now! Still find dewlap displaying fascinating, especially with the added component of UV signalling in the mix. That aspect parallels a lot of the stuff with bird signalling. The fact that males are in such close proximity and can see at least silhouettes of others displaying give a certain network component that Pete and I were always interested in pursuing, but just never go around to it. Still occupies my thoughts (hence the cartoons) and talk about it in my lectures, but guess I will have to wait to put it into field practice! Still, next North American Ornithological Congress in 2020 is being held in Puerto Rico….
And here’s another of his drawings:
Earlier this year, we reported that researchers had split the four species of green anoles on Hispaniolia, describing 12 new species. Wasting no time–and with much beauty–the Dominican Republic has placed four of these new species on stamps! Thanks to the world’s authority on anoles on stamps, Uwe Bartelt, for bringing this to our attention.
It’s that twice in the year opportunity to get AA anole watches at bargain basement prices in honor of today’s clock changes. Get ’em before they run out of stock (or, more importantly, before midnight). Use Code:
Aslam Ibrahim Castellón Maure posted this photo on his Facebook page. Taken in the Zapata Peninsula, it’s a Cuban trogon eating an unidentified anole. The Cuban trogon, or tocoroco, is the national bird of Cuba. But what species of anole? Hispaniolan trogons have also been observed eating anoles. More surprisingly, their lovely relative the quetzal has also been reported to do so, notable because quetzals are thought to be primarily frugivorous.
It’s not clear whether Rick Shine would know an Anolis lizard if one hit him on the head, but there can be no doubt that he is a great scientist and herpetologist. Anole Annals is delighted to learn that tonight in Parliament House in Canberra, Australian Prime Minister Malcolm Turnbull will present Rick with the 2016 Prime Minister’s Prize for Science. Previous winners have been biomedical researchers, cell biologists and astronomers, among others. Read all about it here. Congratulations, Rick!
Wendy Lee photographed a Graham’s anole eating another anole, probably an A. lineatopus. The event went down on November 25, 2013 in Runaway Bay, Jamaica, where Wendy runs a wildlife rescue facility, the Seven Oaks Sanctuary for Wildlife. We’ve discussed anoles eating other anoles several times in these pages, most recently with regard to A. sabanus.