Anole Annals

Husak Lab member Erik Sathe putting a lizard through its paces. Photo by Jerry Husak

AA contributor Jerry Husak has just published a great paper in The Journal of Experimental Biology on the effect of training (=practice) on the sprinting and endurance capabilities of green anoles. The Inkfish blog on Discover magazine’s website has written a brilliant description of the study:

Athletes don’t normally need to be chased down the track to get their training mileage in. But a green anole lizard is not a normal athlete.

Scientists wanted to know whether it’s possible to train a lizard at all. Human athletes and other mammals perform better with consistent exercise, but is this universal? Can a reptile increase its stamina? What about its sprint speed? So the scientists became lizard athletic trainers, which really means lizard harassers. Results were mixed.

The green anole lizard, or Carolina anole (Anolis carolinensis), is a common laboratory species. Basic rules of its biology—for example, how it responds to exercise—ought to apply to other vertebrates, such as humans. In the past, scientists have successfully used exercise to increase endurance in frogs, birds, alligators and crocodiles. But the same efforts with lizards have been inconclusive.

Jerry Husak, a biologist at the University of St. Thomas in Minnesota, studies lizards with the help of undergraduate researchers. He and his students decided to try creating “Olympic lizards.” They would train their subjects for two kinds of athletic ability, neither of which was totally foreign to the reptiles. Some lizards would become endurance athletes; this long-distance locomotion would mimic the slow patrolling and foraging anoles do in nature. And other lizards would become sprinters; in nature, they use bursts of speed to escape predators.

Thirty lizards were divided into sprinters, distance runners, and a control group. The sprinting track was a dowel two meters long and five centimeters wide, propped at a 45-degree angle. The researchers chased the lizards up the dowel and used infrared beams to measure their fastest speed. Sprinters “trained” three days a week for eight weeks. Gradually, the researchers increased the training intensity by making the lizards do more runs per day.

Meanwhile, the distance runners did their training on a treadmill. The researchers set the treadmill to a low speed and gently prodded the lizards with a paintbrush to keep them moving. These athletes had to stay on the treadmill for 30 minutes at a time, or until they were exhausted. (How do you know anoles are exhausted? “When we flip them over onto their backs and they can no longer flip themselves back onto their feet,” Husak explains. Glad he’s not my trainer.) These lizards, too, exercised three times a week for eight weeks, while the steepness of the treadmill gradually increased.

At the end of the training regimen, the researchers tested all their lizards a final time. The distance runners had clearly improved. On a fast treadmill, the endurance-trained lizards could run for almost three times as long as they had initially. Blood samples showed that their hematocrit levels—a measure of red blood cells, which carry oxygen—had also increased. And dissecting the limbs of dead lizards revealed that their muscle fibers had grown, just as they do in exercising mammals.

The sprinting lizards were a little more disappointing. In their final trials, they didn’t run any faster than they had before training. But their muscle fibers had also grown. Husak suspects that these athletes had actually improved—they just didn’t feel like performing.

“I definitely think the sprint-trained ones increased their sprinting abilities,” Husak says. But after the lizards had spent so much time being handled by humans, he says, “We just couldn’t motivate (i.e., scare) them enough…to run as fast as they could.”

There’s not likely to be a lizard Olympics anytime soon. Creating athletic anoles isn’t the only goal of Husak’s research, though. He’s ultimately interested in the tradeoffs that come with being a good athlete. Animals that spend more energy on reproduction, for example, may have to sacrifice life expectancy or immunity. Do the same tradeoffs happen when animals spend their resources to build beefy muscles?

Husak has gotten closer to answering that question by showing that lizards can be trained. Now he just has to figure out how to scare them into performing their best—because even if the biology of exercise is the same across vertebrates, the power of a “Just Do It” poster isn’t.

The post doesn’t say much, but it’s nice for this lovely anole to get the attention it deserves!

If you search for photos of A. lividus online, there aren’t all that many. Several more nice ones have appeared previously on AA, such as this one:

Photo by Jim Hewlett

and here’s one from Calphoto:

If you want to read more on this not-well-studied species from an island recently ravaged by volcanoes, AA is the place [1,2].

Photo by Dick Bartlett.

Dick Bartlett found this lizard a week ago, deep in the rainforest along the Rio Mazon, Dpto Loredo, Peru. He says “The blue irises initially indicated transversalis but the more I’ve thought about it, the more unsure I have become.” Anyone able to identify it?

I have heard of the use of sticky traps for studying lizards, though a colleague told me they seem to be of uncertain safety for anoles, as his recapture records were almost nonexistent.

We finally gave up on the “bio-warfare” of feline-infantry to a recent rodent invader to the house, and had to put this trap out last night inside the house. This morning we found the intruder caught in it (juvenile Rattus sp.), but the domestic service lady put it for a minute in the backyard and not long after an Anolis distichus was also caught, probably in the seek of flies stuck to the trap (see photos). She then called me and I used an old trick, pouring (vegetable) oil in the prey in order to make it come loose from the trap’s glue surface.

Could the oil create a thermic or clinging capability problem to the lizard? It obviously forms a coating above scales, hence I rubbed it with napkins and then placed it back to its favorite microhabitat (trunk bark) for it to bask and recover.

The lizard (38 mm SVL) was toe-clipped and marked in the belly and put back in the backyard. Hopefully we can have a recapture in some days (if cats and sparrows don’t get it first).

Phelsuma guimbeaui from Mauritius.

Despite the brilliant colors, the natrual history of day geckos (Phelsuma) is little known. The most recent issue of Herpetological Conservation and Biology includes a very nice study on the habitat use of two Mauritian species, showing that they are most abundant in native forest and pointing out that, thanks to their pollinating services, they are keystone species. An interesting point is that even though day geckos are essentially Old World anole doppelgängers, in their habitat use they differ in rarely leaving the trunks of trees. One of the authors is legendary ornithological conservationist Carl Jones, almost single-handedly responsible for preventing the extinction of several Mauritian bird species.

Here’s the abstract:

Many fragile ecosystems across the globe are islands with high numbers of endemic species. Most tropical islands have been subject to significant landscape alteration since human colonisation, with a consequent loss of both habitat and those specialist species unable to adapt or disperse in the face of rapid change. Day geckos (genus Phelsuma) are thought to be keystone species in their habitats and are, in part, responsible for pollination of several endangered endemic plant species. However, little is known about key drivers of habitat use which may have conservation implications for the genus. We assessed the habitat use of two species of Phelsuma (Phelsuma ornata and Phelsuma guimbeaui) in Mauritius. Both species showed a strong affinity with tree trunks, specific tree architecture and are both restricted to native forest. Tree hollows or cavities are also important for both species and are a rarely documented microhabitat for arboreal reptiles. Both P. ornata and P. guimbeaui avoid areas of high disturbance. Our data suggest that active conservation of Phelsuma requires not only the protection and restoration of native forest, but also implementation of forestry practices designed to ensure the presence of suitable trees.

Anolis sagrei. Photo from Wild about Spain

An important problem in climate change biology is understanding how evolutionary dynamics will influence the ability of populations or species to persist as environmental conditions change. In general, there are three ways that such evolutionary change can occur: (1) novel beneficial mutations can arise de novo; (2) rare alleles within a population can become beneficial and sweep to fixation; or (3) gene flow between locally adapted populations can introduce beneficial alleles to populations that did not previously have them. The potential for this latter scenario was investigated by Mike Logan using A. sagrei on a system of cays off of the Bahamian island Exuma. Mike measured operative thermal environments on the cays and Exuma, as well as temperature-dependent physiology of the animals in each population. He found that the islands differed in mean temperature and variability, and that optimal temperatures for physiological performance correlated with mean island temperature. Next, Mike used genetic markers to estimate population structure and rates of migration between the keys and the mainland. He found evidence for extensive gene flow between the populations, but with an interesting twist: gene flow was highest between populations that had the most similar thermal environments. Within the context of climate change, the observation of gene flow among islands based on thermal conditions suggest that as conditions change across a species’ range, beneficial alleles may be able to move into the populations where they are needed most. Mike’s work adds an important piece to an emerging picture about the interplay between standing genetic variation, local adaptation, and responses to global change.

We’ve had a number of previous posts on orange-colored brown anoles, but here’s a nice blog post that discusses them a bit further, with a bonus photo of a yellowish green anole. Christina Chappell, the majordomo of serenityspell.com, reports that the lizard was seen in the northern part of the Everglades. And, no, in case you’re wondering, the photo was not altered in any way.