Mystery Anole
Can you identify this species? It was recently observed in Pinellas County in Florida, where Anolis sagrei is established but not any other Anolis spp. This photo is your only clue.
Read the sad details on Project Noah. We’ve reported on saurivory in spiders previously, most recent a Nephila eating a brown anole.
Anolis nebulosus
In a recent paper in the Italian Journal of Zoology, Senczuk and colleagues report an interesting finding on the clouded anole, Anolis nebulosus. On the mainland, the species is fairly petite, with males averaging 40 mm SVL. However, on a very small, offshore islet, only half a kilometer from the mainland, males grow to an average of 53 mm, and the average female is larger than the largest male on the mainland.
What is responsible for such great disparity in size? Two prime possibilities are that most of the anoles predators are absent from this small island and that the island has a seabird colony, which may lead to greater quantities of insect prey.
In a fascinating previous study, some of the authors of this paper documented many other interesting differences between the mainland and island populations, such as the fact that lizards in the island population are much more active and display more. Clearly, this is a situation worthy of further study.
Abstract:
The clouded anole Anolis nebulosus (Squamata: Polychrotidae) is widespread on the Pacific coast of Mexico. The species also inhabits Don Panchito, a small islet located near the coast of the Chamela-Cuixmala Biosphere Reserve in the state of Jalisco. We studied the extent of intraspecific differences in morphology (absolute size and body proportions) and in mtDNA sequences (16S and NDH2) between the population living on the islet (N = 18 for morphometry; N = 12 for mtDNA) and the one on the facing mainland (N = 38 for morphometry; N = 16 for mtDNA). The individuals on the islet are larger than those on the mainland with little overlap in size for either males (islet: 52.79 ± 1.82 mm; mainland: 40.96 ± 2.99 mm) or females (islet: 46.18 ± 3.24 mm; mainland 37.14 ± 2.13 mm). The presence of insular gigantism, as here found in A. nebulosus, seems uncommon in the genus and could be explained as a combination of low predation pressure and higher intraspecific competition on the island. Moreover, we found that sexual dimorphism (SD) is higher in the island population than in the mainland one. The molecular analysis shows the absence of shared haplotypes between the island and mainland populations. Ten mtDNA haplotypes belonged to the mainland population and three to the island population. The shape of the minimum spanning network and of the mismatch distribution indicates a single colonization event. These molecular data indicate a certain degree of isolation of the island population notwithstanding its proximity to the coast. The morphological characteristics of the anoles on Don Panchito match with the expectation of the so-called “reversed island syndrome” theory, which predicts an increased body size and sexual dimorphism in lizards living on very small islands characterized by unpredictable environmental conditions.
Here at AA, we seem to have an obsession, hopefully healthy, for a few things: knight anoles, anoles and water, and big dewlaps. And here’s a combination of two of them, a mainland aquatic anole displaying its enormous dewlap. Wowwee! It’s big and beautiful. What is it with mainland anoles and their big throat fans? This is a youtube video posted by MrKbosker, identified as A. aquaticus.
And not to be outdone, InBio, the Costa Rican biodiversity institute, brings us this mellifluous footage of A. polylepis strutting its stuff.
httpv://www.youtube.com/watch?v=7u9zFMlj7XU
Anolis ventrimaculatus. Photo by Jonathan Losos.
We (Rosario Castaneda, Anthony Herrel, Luke Mahler and I) have just completed the first leg of our 2.5 week Colombian anole sojourn. First up: La Cumbre in the hills north of Cali. At 2000 meters, it was chilly! Going out our first night, we found plenty of long-legged Anolis ventrimaculatus. Imagine our surprise the next day when they were hard to find when active! This was reminiscent to us of A. gemmosus in Mindo, which also is very abundant at night–we’re talking Caribbean anole night abundance–but not easy to find while active.
The ones we did find were generally low to the ground, often on tree trunks, sometimes on vegetation. They refused to move when we filmed them, but their stomach contents indicated that they had been foraging, even at temperatures in the upper teens. These are tough, wily buggers!
We found two other species in smaller numbers, but only at night. The most exciting was A. calimae, which was not known from the locality at which we were working. We found a male and a female. They look moderately like twig anoles–elongate, slender body habitus–but there limbs are on the long side. We’ll see what the morphometrics say. However, when we released them, they behaved exactly like twig anoles, squirreling to the far side of a branch, creeping forward, carefully placing one foot, then the next, freezing. Unfortunately, despite intensive efforts, none were located during the day, perhaps not surprising, as many twig anoles are very cryptic and hard to find, particularly given that they live in dense vegetation.
Female Anolis calimae. Photo by Jonathan Losos.
Lastly, we found a number of A. mariarum in dense fields of high, stout grass. The photo below shows one such area. These lizards have to be living in the grass; they’re too far from anything else (the occasional tree notwithstanding. Yet search as we might, we couldn’t find them during the day. Our guess is that they are active in the spaces on the ground beneath the grass. In fact, when we let the lizards go, they seemed quiet happy to scamper about, and even display at each other, under the grass canopy.
Anolis mariarum’s field of dreams, where several were found sleeping, but none could be found during the day.
An exciting, if chilly start, but we’ll soon be thinking wistfully of cool days and evenings as we head to our hot and steamy next location.
Martin Whiting of Macquarie University began his talk at the Animal Behaviour Society 2014 meeting by lamenting how little we know about the social lives of lizards, especially when compared with mammals, certain insects and fish, and most of all, those pesky other reptiles, birds. But the more we examine lizard social behaviour and cognition, the more apparent it becomes that these animals are capable of substantially more complexity than we previously thought possible. Whiting presented some recent research on the Eastern Water Skink, Eulamprus quoyii, that bolsters this view.
Eastern Water Skink, from the Whiting Lab Page
Though not often social, many lizards, including Eastern Water Skinks, live at densities high enough to allow individuals to be within sight of each other. This is a sufficient prerequisite for social learning, defined as learning a task by observing others and modifying one’s own behaviour accordingly. Whiting asked whether Eastern Water Skinks were capable of social learning by training “demonstrater” individuals to perform certain tasks, letting “observer” individuals watch these demonstraters, and then measuring whether this exposure to the demonstraters enhanced the observers’ success at the task at hand.
The answers to Whiting’s questions were not simple. First, age matters—young individuals were twice as likely to demonstrate social learning than old individuals. Second, the task matters—lizards learnt to associate a colour with a food reward by watching others, but the prerequisite task of actually flipping over the coloured cap to access a mealworm was not spurred by observing other individuals do the same.
In the future, Whiting and his students hope to conduct similar experiments with a variety of lizard species that differ in their degree of sociality. These experiments will definitively address the role of learning in shaping the social lives of lizards, and I can’t wait to see they find!
When I think of colour and pattern in lizards, I tend to think about showy visual displays. An example that springs to mind is this fantastic footage of Draco lizards using multiple appendages as colourful signals.
But despite all the effort an individual lizard puts into signalling to conspecifics, it must constantly remain wary of predators. Mimicry and camouflage are tried and tested means by which to evade predation, but little effort has been made to quantify the colours and patterns that may help lizards escape being eaten. Research presented by Danielle Klomp from the University of New South Wales at the Animal Behaviour Society 2014 meeting addresses this question in Draco cornutus, a South East Asian agamid lizard that uses the patagium, an extendable membrane attached to elongated rib bones, to glide from tree to tree.
Sampling in two populations of D. cornutus, Klomp noticed that though individuals in the two populations had identical dewlaps, they differed substantially in the colour and pattern of the patagium. Remarkably, the colours exhibited in each population seemed to perfectly match the colour of falling leaves of trees in the same habitat.
Patagia and falling leaves from two populations of Draco cornutus. Photos by Danielle Klomp.
By measuring spectral reflectances as well as the proportions of black on lizard patagia, falling leaves, foliage, and dead leaves, and accounting for how these colours might appear to predatory birds, Klomp demonstrated that in both colour and pattern, D. cornutus patagia in each population most closely matched falling leaves in the same population. This suggests that Draco are especially vulnerable to predation while gliding, and have undergone strong natural selection to mimic non-prey items in the particular environment they experience while gliding.
Here’s a link to Klomp’s poster from the International Society for Behavioural Ecology 2014 conference, and here’s a link to a blogpost about some very cool technology that Klomp used to make her poster come alive while presenting it.
From Rachel on Twitter.
Wouldn’t this be great? Maybe there’s one out there, still waiting to be discovered.
httpv://vimeo.com/93621704
We’ve discussed the crisis concerning Jamaica’s Goat Islands previously. This film is the work of Robin Moore. Read more about the film and the efforts to preserve Jamaica’s iguanas on National Geographic‘s Newswatch. More relevant videos can be viewed at the Save Goat Islands website.
Here’s the first lizard talk from the Animal Behavior Society meetings! This is a guest post from Holly Brown, who studies visual and foraging ecology in herons at UConn.
Eye structure is remarkably similar among vertebrates. Therefore, one might, understandably, imagine human visual experiences to be representative of visual experiences across vertebrate taxa. However, this is not the case. Two important differences between mammalian and non-mammalian vertebrate vision are that, unlike us, the latter are able to move their eyes independently of one another, and they seem to lack stereopsis. Stereopsis is the ability to view the two independent images generated from each eye as a single image, which ought to make depth perception easier, and thus aid in important tasks such as capturing prey.
So instead of studying mammals, Gadi Katzir and his team of collaborators from the University of Haifa, Israel, are studying chameleons to better understand vertebrate vision.
Common Chameleon by Benny Trapp from Wikimedia
One of their recent experiments was aimed at finding out whether or not chameleons could simultaneously track two prey items independently with each eye, and if so, how independently (of one another) were the eyes able to move. They found that chameleons could simultaneously track different prey items with each eye, but at some point, they would always make a choice to converge both eyes onto their eventual prey target. Furthermore, they found that chameleons never struck at prey with their eyes still diverged. By pursuing this line of research, Katzir and his team may be able to glean insights as to how stereopsis may have evolved.