Category: Natural History Observations Page 4 of 34

An adult male San Salvador Bark Anole (Anolis distichus ocior) displaying.
Photograph by Guillermo G. Zuniga.

Dayton Antley and colleagues from Avila University, the home of AA stalwart Bob Powell, recently published a detailed study of the ecology of the San Salvador bark anole (Anolis distichus ocior) in IRCF Reptiles & Amphibians (an open-access herpetological journal, with this article available here). Anolis d. ocior is one of 17 recognized subspecies of the diverse distichus group, and is found on only San Salvador and Rum Cay (Henderson and Powell 2009).

Antley et al. assessed microhabitat use, activity patterns, and approach distances of A. d. ocior in an approximately 0.3ha study area on the grounds of the Gerace Research Centre, dominated by Tropical Almonds (Terminalia catappa), Papaya (Carica papaya), and Ficus trees.

A Google Map view of the Gerace Research Centre. The study site
(24°07’05.2″N 74°27’50.9″W) is outlined in white.

In assessing patterns of microhabitat use throughout the day, Antley et al. conducted surveys every two hours for two days from 0700h (about 40 min after sunrise) to 1900h (about 40 min before sunset). Size class, perch height and diameter, body orientation relative to the ground, and thermal microsite (sun/shade/mixed) were recorded for every observed lizard. In the following two days, approach distances were assessed. This was achieved by a surveyor, wearing neutrally-coloured clothing, approaching an undisturbed anole at a steady pace and recording the distance at which the lizard reacted. Over two additional days, 10-minute focal animal observations were conducted of individual adult lizards (including both males and females) at a distance of 5m. The number of movements (changes in location or orientation), head turns, and head bobs were recorded for all lizards, with dewlap displays and pushups being additional recorded for males.

Lizards were active throughout the day, with activity peaking in the early morning and before midday. This was compared to ambient air temperatures recorded 1m from the ground in a shaded and sheltered location. This result surprised the authors, as a second activity peak in late afternoon/early evening was expected, as has observed in other similar studies of bark anoles (e.g. Hillbrand et al. 2011).

Mean number of lizards active (bars) and mean ambient temperatures
(dots) per time period. Temperature data were collected on
two consecutive days.

Adult males experienced highest levels of arboreality during the middle of the day, while subadult males and adult females (grouped together as they can be hard to distinguish from distance) were highly variable (see figure below). Most lizards of all classes were found in the shade, which the authors attributed as evidence for thermal conformity, and facing downward towards the ground, a common trait in many anoles that is most commonly perceived to increase an individual’s ability to monitor potential predators, competitors, or mates. 43% of lizards, however, were observed facing upwards. The author’s note that this behavior is often interpreted as an individual prepared for escape; however as all lizards were observed from distance and undisturbed, they (admirably) explain that this result is difficult to interpret.

A: Mean perch heights (cm) of adult males (L) and subadult males and females (S); B: mean perch heights of adult males at different times of day;
C: mean perch heights of subadult males and females at different times of day.

Adult male lizards were bolder than smaller subadult males and females, and retreated at a much closer distance when approached by a surveyor (0.99m +/- 0.07m vs. 1.54m +/- 0.18m). Focal observations revealed no significant differences between adult males vs. subadult males/females in shared behaviors, although there was a high variation in the amount of displaying behavior between adult males. The average time spent conducting dewlap displays was 3%, although one male was recorded investing 47% of his time in a combination of dewlap extensions and pushup displays.

Using all survey data combined, Antley et al. estimate that A. d. ocior in this study plot had a population density of 593 individuals/ha, with lizards observed on all but four of the smallest trees surveyed. Antley et al. note that their density estimate is extremely conservative, and much lower than previously published estimates (e.g. 1.070-5,460 individuals/ha, Schoener and Schoener 1978). The authors suggest that the small size of the study plot may have contributed to the relatively low density.

In all, this is a charming (although admittedly short) study of the natural history of the San Salvador bark anole (A. d. ocior) – a great example of an undergraduate research project that follows through to publication!

References
– Antley, D.L. et al. 2016. Microhabitat, Activity, and Approach Distances of the San Salvador Bark Anole (Anolis distichus ocior). IRCF Reptiles & Amphibians 23(2): 75-81
– Henderson, R.W. and R. Powell. 2009. Natural History of West Indian Reptiles and Amphibians. University of Florida Press, Gainesville, Florida.
– Hillbrand, P.A., A.T. Sloan, and W.K. Hayes. 2011. The terrestrial reptiles of San Salvador Island, Bahamas. Reptiles & Amphibians 18: 154–166.
– Schoener, T.W. and A. Schoener. 1978. Estimating and interpreting body-size growth in some Anolis lizards. Copeia 1978: 390–405.

Paragliding Anoles?

By Bruno de Medeiros

On August 4, 2016

In Natural History Observations

Anolis chlorocyanus after gliding back to the tower. Photo by Brian D. Farrell

Every summer, a group of students heads down to the Dominican Republic to take the Harvard summer course on biodiversity of the country. As a teaching assistant, I often watch unsuccessful attempts of students trying to catch the abundant fast-moving lizards. Sometimes I also participate, usually resulting in the same outcome. Last week, we were climbing an observation tower in Punta Cana to spot Ridgway’s hawks (Buteo ridgwayi) when Ryan Friedman, a student taking the course, noticed a Hispaniolan green anole (Anolis chlorocyanus) perched on the side of the tower. We thought we would finally outsmart an anole and catch it with our hands. However, the lizard apparently preferred to jump to certain death rather than being handled by us. We watched it falling down about 10 meters, but, instead of going straight down and hitting the ground, it followed a curved trajectory that safely brought it back to the tower (and enabled Brian Farrell, the course instructor, to take a picture after the fact).
This observation seemed remarkable enough for Jonathan Losos to allow this entomologist to report it here, and also made me very curious. Are some anoles able to direct their fall, or maybe to glide with the wind while they go down? Hopefully someone will have the chance to do a controlled trial and figure it out!

Editor’s Note: Such behavior has been noted for Anolis pentaprion.

Prince of Thar–Sands of Time…

By Harsimran Singh

On June 28, 2016

In Natural History Observations

An adult nipping grass in the morning; notice the bluish tinge on the inner side of the thigh and dorsal part of tail.

Here is Saara hardwickii , spiny tailed lizards. I observed these lizards in their natural habitat, in the Thar desert in Indian state of Rajasthan. It’s a medium-sized lizard which dwells in semi-arid to arid landscapes of northern India, Pakistan and some regions beyond. A drab colored lizard with a pug head and a distinct fleshy and spiny tail.

Habitat fragmentation and hunting for its tail is the main reason for its dwindling numbers. Folklore has it that its tail has aphrodisiac powers, so its tail is cut and ‘oil’ extracted from it and consumed for the intended purpose.

Interestingly, like iguanas, these lizards also live in a social structure, a ‘society’ composed of adults as well as young ones. They live in ground burrows or termite mounds. Spiny-tailed lizards are diurnal; their activity starts around early morning sun and when the sun sets, surprisingly not even a single individual can be seen! A considerable ontogenic shift in dietary inclination towards herbivory can be seen. Adults feed on grass or diminutive terrestrial flora, whereas young ones are omnivorous, feeding on arthropods.

This fellow was just out of its home and carefully observing its habitat.

Three-Legged Green Anole

By Joshua Hall

On June 24, 2016

In Natural History Observations

There are several previous posts concerned with lizards missing feet or limbs (1, 2, 3). At the risk of being monotonous, here is another. I caught this male green anole (Anolis carolinensis) in Auburn, AL this morning (6.24.16). He was sitting on someone’s porch railing at my apartment complex. In addition to his front left limb he was missing 2 fingers on the front right hand and one on the back left foot. He has no other signs of damage, however, not even any evidence of a regenerated tail. I think what sets this example apart from ones previously given is that the entire limb is missing. There is only a tiny nub of bone at the shoulder, and a small flap of skin. Interestingly, the tiny nub moves back and forth beneath the skin when he runs, as if the entire limb were still present and useful.

We (Warner Lab) have had lizards hatch without limbs in the past. We even had one (A. cristatellus) hatch this year with 6 limbs (three front right arms). It is possible that this carolinensis never developed this limb to begin with; however, the tiny flailing nub and flap of skin make me feel that is not the case. Anyhow, this guy seems fat and happy and still moves pretty fast, despite the handicap.

Dewlap Displays in Cuban Knight Anoles (A. equestris)

By James T. Stroud

On June 17, 2016

In Anole Photographs, Classics from the Literature, Introduced Anoles, Natural History Observations, Notes from the Field

While exploring the grounds of Fairchild Tropical Botanical Gardens with Janson Jones this past weekend, we extremely fortunately happened upon a large adult male Cuban knight anole (A. equestris) in full displaying swing. Despite the fact that knight anoles have an impressively large dewlap, I have often found this to be a relatively rare event, as large crown-giant species tend to display less than other smaller and more active species. This individual was displaying at a height of ~15 m, just below the fronds of a large Royal Palm (Roystonea regia). We didn’t see any other neighboring knight anoles, so were unsure if this was a directed or passive display series. In all, this lizard performed perhaps 4-5 sets of dewlap displays (each comprising of 4-5 dewlap extensions) before stopping and retreating back into the canopy.

Anoles typically follow a predictable and repeated pattern of display that gradually increases in intensity. Initially, and rather lethargically, an individual will nonchalantly raise its head and extend its dewlap without much extra effort (stage a); described below from Losos (2009).

Adapted from Losos (2009), which itself is adapted from Losos (1985). Aggressive behavior of A. marconoi showing three stages of increasing display intensity – note stage (c) include full body elevation alongside simultaneous tail and dewlap extensions.

This then escalates to include a slight body raise (stage b).

And ultimately results in a dramatic finale – in full display all limbs will be extended to raise both their body from the substrate (in this case the trunk of a palm tree) and elevate their tail (stage c). In the following picture you can see this final stage of displaying where intensity peaks – albeit in this individual with a regenerated (and rather stubby) tail.

Aquatic Anole Sleep Site Fidelity

By HannahKimFrank

On May 5, 2016

In Natural History Observations

Juvenile Anolis aquaticus wakes up for science, Photo: Jonathan Flanders

One of the many wonderful things about anoles is that anole-hunting can be a 24/7 experience, as many nocturnal Anole Annals adventurers have shown and I’ve noted before. As an undergraduate, I spent many days and nights scanning trunks, leaves, sticks, bushes, etc. for anoles — a habit that got so ingrained that I still do it while hiking around northern California. So, logically, when I found myself in Costa Rica for the last field season of my Ph.D. (which is on bats), I had to do some lizard spotting, if only to remind myself of the good old days when I studied animals that don’t fly or bite. (Ok, anoles bite but that’s what makes them such great fashion accessories.) As I was already up until all hours of the night, I decided to check out where anoles were sleeping. There happened to be a small group of aquatic anoles living near my cabin and I (along with my batty colleague) noticed that each night they seemed to be in the same place — one email to Jonathan later and we wrote up a short note for Herpetological Review about sleep site fidelity in Anolis aquaticus.

Who turned the sun on? Photo: Jonathan Flanders

We observed the lizards for 16 nights over a period of 24 nights and found that of the six individuals, they were in the same place almost 80% of the nights, which is very high compared to what has been found in some other species. All of the lizards were perched in such a way that they were either obscured from view or had easy access to water to escape from predators. The area was particularly dry at that time so this may have reduced the number of suitable sleep sites for these aquatic lizards or maybe aquatic anoles are just pretty faithful to their sleep sites. In any case, it was a lot of fun to go back to my lizard-y roots and find some sleepy anoles.

Meanwhile in a Parallel Universe…

By Harsimran Singh

On April 16, 2016

In Natural History Observations

At the other end of the world in the Indo-Malayan realm (in India, down south in the sky islands of Western Ghats), a Calotes rouxii male is advertising itself. He is displaying his bright red head on its black body. Even the dewlap region is almost black. Facial region is almost completely bright red along with nuchal and spinal crest. Male display of this lizard is like many Anolis sp. A male typically does some pushups , ducks and bobbles his head to display his dominance in physical prowess and colour.

Calotes rouxii male.

Female or juvenile male of Calotes rouxii.

Calotes rouxii male

Spring Break Herp Style

By Nick Herrmann

On April 4, 2016

In Natural History Observations

“This is not a Spring Break trip to Costa Rica, it is a herpetology class trip to Costa Rica that happens to be over Spring Break.” So said Jonathan Losos to a room full of eager students, many of whom had chosen to take Herpetology in part because of the adventure that awaited them. As first year Ph.D. students in the Losos lab, we were as excited as anyone for the opportunity to see some of Costa Rica’s rich biological diversity. Plus the well-publicized stereotype of how young people spend Spring Break has never really appealed to us. We’d rather be in the nighttime forest with a headlamp.

The lichen anole, A. pentaprion

The trip started with a day and a half at Veragua Rainforest. We saw tons of frogs and a handful of snakes, but anoles were hard to come by except for a few individuals along shallow, slow-moving streams (A. humilis, A. limifrons, and A. oxylophus). One of our most exciting finds of the trip was along one of these streams – an A. pentaprion hugging a narrow stem at eye level. It was shocking to see this lizard so close to the ground as it is often found high in the canopy and has even been observed gliding between perches. While many mainland anoles don’t fall clearly into the classic ecomorph categories, this lizard, with its small legs, long body and head, and slow but sneaky evasive behavior, is very reminiscent of West Indian twig anoles (and he’s got a gorgeous dewlap too! see photo at end of post).

From Veragua we moved to La Selva Biological Station where we spent five action-packed days exploring the forest and documenting the herpetofauna.

Brown Anole Predation by Red-bellied Woodpeckers in Florida

By James T. Stroud

On March 22, 2016

In Introduced Anoles, Natural History Observations, Notes from the Field

While visiting relatives last week in Fort Myers (FL), anole enthusiast and avid wildlife photographer Kyle Wullschleger noticed a commotion among the trees while on an afternoon hike in a small neighbourhood nature preserve. On closer inspection he witnessed a group of red-bellied woodpeckers (Melanerpes carolinus) foraging on surrounding cypress trees, with a couple eventually appearing with their apparent target–non-native Cuban brown anoles (A. sagrei). He recalls some of the details:

“The photos from the sequence aren’t all that fantastic because I cropped in so it really just shows the behavior. The whole sequence the woodpecker was basically just slamming the anole against the tree and then trying to pick it apart – it was hard to tell what exactly it was doing, but I believe it eventually swallowed it whole before flying away–it hopped behind the tree so I couldn’t see it anymore.”

“There were at least five birds all moving up and down the lower third of the cypress trees just around the boardwalk I was on. They were moving around the trees without really knocking the wood, so maybe they were purposefully targeting anoles? I only saw successful predation twice, but the brush is so thick–it’s obviously happening quite a bit.”

Sean Giery had previously discussed the main avian predators of anoles in urban South Florida, but woodpeckers didn’t make the list. Woodpeckers do occur in urban areas of South Florida; a new one to add to the list?

On the importance of Dorsal and Tail Crest Illumination in Anolis Signals

By James T. Stroud

On March 4, 2016

In All Posts, Introduced Anoles, Natural History Observations, Notes from the Field

With a flurry of recent attention investigating how background light may influence the signalling efficiency of Anolis dewlaps (1,2,3,4), particularly those inhabiting low-light environments where patches of sunlight appear at a premium, it occurred to me that extended dorsal and tail crests may fall under similar selection. Below are some photos of Puerto Rican crested anoles (Anolis cristatellus) – a species in which males exhibit an enlarged tail crest and the ability to voluntarily erect impressive nuchal and dorsal crests during aggressive interactions (the mechanisms of which are detailed in this previous AA post) – that show how crests may contribute to signalling.

I have no doubt this thought has crossed the minds of many anole scientists before, particularly those current graduate students so successfully studying A. cristatellus and familiar with their ecology and behaviour (namely Alex Gunderson, Kristin Winchell, Matt McElroy, and Luisa Otero). Dewlaps are undoubtedly of primary importance to anole signalling and communication, but what are people’s general thoughts on the relative importance of other morphological features?