Aposematic warning patterns are supposed to have evolved to warn potential predators to stay away. But do they work? An experimental study at the La Selva Biological Station in Costa tested that hypothesis on common ground anoles, Anolis humilis. Baruch et al., writing in the Journal of Herpetology, presented the anoles with clay models painted in an aposematic or cryptic color. The models were dangled in front of the lizards and wiggled around, simulating a flying insect. Sure enough, the lizards went after the cryptic models nearly half the time, but almost completely ignored the orange and black ones. Aposematic patterns work!
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Here at AA, we love lizards with horns on the tip of their snouts. The horned anole, Anolis proboscis, is of course our favorite, but there are others. For example, Sri Lanka is home to the little known Ceratophora stoddardi. Anima Mundi, an online magazine produced by an Italian husband-and-wife team, just had a nice seven page spread on this species, which it dubs the “rhino lizard,” replete with beautiful photos and a bit of natural history information. Like the horned anole, the rhino lizard can move its horn! I wonder what would happen if they ever met. Who knows? But if you want to learn more about the rhino lizard, check out our previous post on the species.
Two years ago, the Museum of Comparative Zoology published Randy McCranie’s book on the anoles of Honduras. Now, the MCZ is soon to publish Randy’s latest work, a massive compilation on the lizards, crocs and turtles of Honduras, to be titled, appropriately enough, The Lizards, Crocodiles, and Turtles of Honduras: Systematics, Distribution, and Conservation.
How would you like your photograph to grace the front or back of this forthcoming volume? We’re looking for beautiful photos of Honduran lizards, crocs or turtles. The front cover photo must be vertical in aspect, the back cover horizontal. We can’t offer to pay you, but we’d be happy to provide you with a copy of the volume when it appears.
Please send photos to anoleannals@gmail.com
Thanks!
The use of programmable robots (‘mechanical models’ is more accurate) to minimise disturbance while observing wildlife, or to run behavioural experiments in the field, has slowly increased in the last decade and studies across many taxa have utilized this approach (Martins et al., 2005; Partan et al., 2009; Cianca et al., 2013; Macedonia et al., 2013; Clark et al., 2015). I’d argue that “robots” are one for the most important tools for behavioural ecologists studying communication or display behaviour, as they are one of the few ways in which we can conduct field-based experiments – mimicking or manipulating animal behaviour, colour or morphology in any way – in the animal’s natural environment.
We recently published a paper in the Journal of Evolutionary Biology, using robots in playback experiments to test the importance of ornament design for signal detection and conspecific recognition.
Many factors potentially affect signal design, including the need for rapid signal detection and the ability to identify the signal as conspecific. As understanding these different sources of selection on signal design is essential in the larger goal of explaining the evolution of both signal complexity and signal diversity, here we assessed the relative importance of detection and recognition for signal design in the Black-bearded gliding lizard, Draco melanopogon (fig. 1). Lizards of the species-rich genus Draco use large extendible dewlaps for communication, that differ in colour pattern and size between species – in a similar fashion to the anoles.
Figure 1 A. Male D. melanopogan, dewlap naturally extended (image a still from behavioural trials) and the angle of dewlap extension as measured from still; B. robot, dewlap treatments (Bi) solid colour and Bii) two-coloured); and C. artificially extended dewlaps of a male and female D. melanopogan.
To test whether the dewlap colour and pattern function more to facilitate 1. signal detection and 2. conspecific recognition, we presented free-living lizards with robots displaying dewlaps of six different designs, varying in the proportion of the black and white components.
In this case, our robots were just ‘visual flags’ that mimicked the dewlap size and shape, as well as the speed and display pattern of live Draco melanopogan lizards (video 1). Having only the dewlap / visual flag and not the rest of the lizard body allowed us to look solely at the salience of the dewlap colour and pattern itself – without adding any identifying or qualifying information in the form of a body.
Video 1: ‘The floating dewlap’
Our experiment had six colour treatments ranging from “natural” (population typical design, fig. 1) to unnatural (wrong colour, no pattern) – and from very conspicuous (high internal contrast and high contrast against the background for each colour) to very inconspicuous (matching the luminance of the background). Thus, we could test both the ‘detection’ and ‘conspecific recognition’ hypotheses with the same set of treatments.
Predictions for Hypothesis 1: We predicted that should the dewlap colour pattern function in signal detection, that more conspicuous dewlap treatments would be detected sooner than less conspicuous dewlaps. Each of the two-coloured treatments were more conspicuous than the single-coloured treatments, as they had the same high contrast black and white elements, but they also had the high internal contrast of the black against the white (75.02 JND). Provided the receiver has sufficient visual acuity at the viewing distance to be able to distinguish the two colours from one another, internal contrast increases signal conspicuousness, and the more equal the two adjacent colour patches are in size (i.e. 50% of the dewlap black – 50% of the dewlap white) the greater the internal contrast. There is no existing data on the visual acuity of Draco lizards, so for this experiment we stuck to the natural dewlap size and viewing distances, with small oscillations around the natural proportions of black and white.
Habitat characteristics influence the efficacy of animal signals, which means that populations of the same species occurring in distinct habitats are likely to show differences in signal structure as a form of local adaptation. This kind of variation in signal structure has been well-studied for sound and colour signals, including in several species of anoles, but had not been reported for motion-based signals until recently.
Jacky dragons (Amphibolurus muricatus) are Australian agamid lizards well-known for the complex motion-based displays performed by males. These displays comprise five distinct motor patterns utilised in sequence: tail flicks, backward limb wave, forward limb wave, push up and body rock (A. muricatus display video). A study conducted by Barquero et al. (2015) found evidence of temporal and structural variation in the core display of three populations of A. muricatus. These differences were not related to genotypic differences between populations, so they suggested they might be a consequence of local habitat structure.
Concurrently, Richard Peters and I were developing a methodology to accurately quantify the effect of background noise on the motion based signals of different Australian agamids (see Ramos & Peters 2017a; b). Our approach calculates the speed distributions of the motion produced by lizard signals and the environmental noise independently. It then compares these distributions to obtain a measure of signal-noise contrast. This is accomplished by recording lizard behaviour and reconstructing its motion in three dimensions before comparing it against the motion produced by the surrounding windblown plants, which are the main source of noise for motion based lizard signals. This methodology stands out from other approaches for quantifying motion signals because it does not assume that the camera is ideally placed when recording the displays, but instead provides an accurate representation of the motion from any angle or viewing position.
Building upon the work by Barquero et al. (2015), we applied our novel approach to a couple of populations of Jacky dragons with distinct habitat characteristics. Croajingolong National Park in Victoria (Australia) is densely vegetated coastal heath with tall grasses and shrubs on a sandy substrate. Conversely, Avisford Nature Reserve in New South Wales (Australia) is mostly open woodland with an understory of scattered grasses and small shrubs, and rocky outcrops spread throughout the park.

The habitats of (a) the Jacky dragon. (b) Croajingolong National Park, in coastal Victoria, Australia. (c) Avisford Nature Reserve, in New South Wales, Australia.
Our results revealed that lizards from the densely vegetated habitat (Croajingolong NP) performed displays of longer duration and introductory tail flick components, and also produced a significantly greater amount of high speeds. However, when we calculated the signal-noise contrast for both populations at their respective habitat, we found no difference. This means that the signals from both populations are equally effective when used within their intended habitat, regardless of their structural differences.

Differences in signal structure between populations. (a) Mean bout and tail flick durations for both lizard populations. (b) Mean tail flick to bout ratio for both lizard populations. (c) Average kernel density functions for both lizard populations.
As mentioned before, our approach records animal signals and environmental noise independently, which allowed us to consider signals not only in the environment where they were filmed, but also in the habitat of the other lizard population. Consequently, to highlight the effects of the environment on lizard signals, we calculated signal-noise contrast for the signals belonging to one population in both habitats (densely vegetated vs. open woodland). As expected, both lizard populations performed worse in densely vegetated habitat, probably because the complex understory is producing greater motion noise and negatively affecting signal efficacy. Another way of looking at these data, but this time focusing on the displays rather than the habitat, was to compare the signal-noise contrast of both lizard populations in a single habitat. Lizards originating from the densely vegetated habitat produced higher contrast scores in both habitats, indicating that their displays are more effective overall.
Taken together, our results are consistent with the local adaptation hypothesis. Lizards from Croajingolong NP produce displays with longer durations and characterised by faster speeds in order to communicate effectively in a dense and noisy habitat. Conversely, lizards from Avisford NR have adapted to a less noisy environment and do not require such lengthy or energetically expensive displays. Such population level differences in signal structure due to habitat variation represent novel findings for motion-based lizard signals.
In the past, numerous anole enthusiasts have posted photos of atypical color variants (1, 2, 3, 4). While sampling small spoil islands in the intracoastal waterway last October, I caught a male brown anole with an unusual splash of color on the shoulder (Fig 1). Reports of sagrei that are completely orange have been noted (5, 6); however, those animals appear to represent a more intense version of the ‘rusty red’ that many of these lizards commonly display on their bodies, particularly on the head. The orange on this male, however, is unlike anything I’ve seen on a brown anole, save for the coloration outlining the dewlap. I’m curious to know if anyone has seen something like this before.
Habitat partitioning due to species coexistence and its implication for species divergence has been the subject of intense research in evolutionary biology. However, its effect on lizard thermoregulation behavior and effectiveness has largely been neglected. Along with Grigoris Kapsalas, Efstratios Valakos and Panayiotis Pafilis, we recently published a paper in the Journal of Thermal Biology, demonstrating that habitat partitioning is responsible for essential divergence in environmental temperatures, while it also promotes deviations in species thermal preferences and thermoregulatory behavior.

Lake Doxa at Feneos plateau, Peloponnese, Greece (image from: http://www.digiwebart.gr/portfolio_page/der-spiegel-cover-art/).
This work took place in a narrow mountain site in Peloponnese (Feneos plateau, Lake Doxa), Greece. Despite its small size, Greece hosts one of the richest herpetofauna in Europe with a total of 86 species (15 of which are endemic). On top of that, Feneos plateau is an amazing place were 28 reptile species coexist and is the only area in Europe where seven lizards of the family Lacertidae occur in sympatry. The first survey at Feneos plateau started in late 1990s and since then the area attracted many herpetologists from different countries.
For the past 20 years our group has worked on the Feneos broader area studying how resource partitioning shifts dietary preferences, digestive performance and species locomotion. In line with these studies, here we focused on three Podarcis (the most predominant and diversified reptile group in Europe) lizard species–Podarcis peloponnesiacus, P. tauricus and P. muralis–and explored how habitat thermal heterogeneity affects the species’ ability for accurate and effective thermoregulation. To assess our objectives, we compared body temperatures (Tb), operative temperatures (Te) and set-point body temperatures (Tset) of the three species.

Frequency of field body temperatures (Tb, dark gray) and operative temperatures (Te, light gray). Vertical black solid lines indicate the set-point range temperatures (Tset).
As expected, niche partitioning resulted in differences in the thermal quality of the microhabitats used by the three species, with P. muralis occupying cooler habitats compared to the other two species. The latter resulted in P. muralis being active at lower body temperatures. Yet, all species thermoregulate effectively and keep their field body temperatures close to their preferred temperatures, indicating high thermoregulation accuracy. Interestingly, the preferred temperatures lizards select in the lab were similar for all three species, despite the differences in the microhabitat temperatures and the lower Tb P. muralis achieved in the field. These findings reveal a rather conservative thermal physiology between these three closely related species. We suggest that by selecting cooler microhabitats and being active at suboptimal temperatures, P. muralis probably avoid or reduce competitive interactions with the other two species.
Paper: Sagonas, K., Kapsalas, G., Valakos, E. & Pafilis, P., 2017. Living in sympatry: The effect of habitat partitioning on the thermoregulation of three Mediterranean lizards. Journal of Thermal Biology 65, 130-137.
Colin Donihue and Anthony Herrel just completed their trip to Redonda to study Anolis nubilus and no doubt they’ll report back to us shortly. Meanwhile, a tip of the hat to AA commenter Nathan Manwaring for pointing out this article posted on Fauna and Flora International’s website:
Captivating Caribbean island to be given a new lease of life
Starving goats and predatory rats to be removed from Redonda to restore this Caribbean island to its former glory.
The Government of Antigua and Barbuda has announced plans to remove goats and invasive rats from its most rugged and remote offshore island to allow endangered wildlife and their habitats to recover.
Redonda is home to a unique array of plants and animals, including rare lizards found nowhere else in the world. The uninhabited and seldom visited island is also formally recognised as an Important Bird Area, supporting globally-significant numbers of seabirds.
However, the island’s plant and animal populations are disappearing fast thanks in large part to its population of over 5,000 aggressive black rats (an invasive alien species) which prey heavily on the island’s wildlife. Together with the herd of long-horned goats that was brought to Redonda by humans more than a century ago, these mammals have transformed this once-forested island into a moonscape. So few plants survive that even the goats now face starvation.
Redonda from the air. The island, once forested, now looks like a lunar landscape. Credit: Jenny Daltry/FFI.
Redonda is over 50 hectares in area and rises dramatically from the Caribbean Sea, 56 km south-west of Antigua. Goat skeletons litter the island, along with the relics of stone buildings from a guano mining community that lived here until the First World War. With few trees left to stabilise the ground, soil and rocks are crumbling into the sea, threatening nearshore coral reef in the waters below.
“We cannot stand by and watch as a part of our country, part of our history, disappears. We cannot be responsible for decimating animal populations on a regional scale,” says local conservationist Natalya Lawrence of the Environmental Awareness Group (EAG).
The Redonda Restoration Programme has been formed by the Antigua & Barbuda Government and EAG in collaboration with partners from the UK (Fauna & Flora International, British Mountaineering Council), USA (Island Conservation) and New Zealand (Wildlife Management International Ltd).
“I am immensely proud that my ministry has been a driving force in the development of this major initiative,” says Honourable Molwyn Joseph, Minister of Health and the Environment. “Restoring Redonda to its full glory will be a great achievement for our country.”
A new home for starving goats
One of the first steps will be to capture and move the remaining goats to Antigua, where they will be cared for by the Department of Agriculture.
The miners also left behind a herd of long herd goats. Together with the rats, these animals have transformed this once-forested island into a moonscape. So few plants survive that even the goats now face starvation. Credit: Jenny Daltry/FFI.
“The goats are starving to death on Redonda and must be removed for their own sake,” explains Astley Joseph, Deputy Director of the Department of Agriculture. “We believe it is important to rescue this rare breed because it could have useful drought-adapted genes that would benefit other herds on Antigua and elsewhere.”
Rats will then be eradicated using a rodenticide bait that has previously been used to restore more than 20 other Caribbean islands without harming native wildlife. This is scheduled to be completed by mid-2017.
Black rats are omnivorous, and are known to attack native wildlife, such as ground-nesting birds and reptiles. Credit: Jenny Daltry/FFI/OICP.
“We and other international organisations have offered our support because we recognise that this is a very challenging yet globally important initiative” says Sophia Steele, Eastern Caribbean Project Coordinator at Fauna & Flora International. “Recent studies have identified Redonda as the most important island to restore in the Eastern Caribbean due to its Critically Endangered wildlife and the high probability of lasting success.”
The new programme is funded by the UK Government’s Darwin Initiative, the National Fish and Wildlife Foundation, the Taurus Foundation and private sponsors. Additional technical and in-kind support is being provided by Caribbean Helicopters and Syngenta Crop Protection AG.
Dr Helena Jeffery Brown of the Department of the Environment says, “Antiguans and Barbudans will be proud as Redonda becomes a role model for regional biodiversity conservation. This will be yet another example of how this country is proactive in meeting the national and international commitments it has made to conserve biodiversity.”
Redonda is also an Important Bird Area thanks to its regionally- and globally-significant colonies of seabirds, including these brown boobies. Credit: Jenny Faltry/FFI/OICP.
Antigua and Barbuda has a wealth of experience and success under the ongoing Offshore Islands Conservation Programme which has, since 1995, removed rats and other invasive pests from 15 islets closer to Antigua in the North East Marine Management Area. This has saved the Antiguan racer – once the world’s rarest known snake – from extinction, and enabled an incredible recovery of other native animals and plants. Many tens of thousands of residents and tourists now visit and enjoy Antigua’s pest-free islands every year.
“I am most excited to see the progression of recovery on Redonda once the threat of invasive species is removed,” says local biologist Andrea Otto, who will be part of the research team documenting the recovery process. “I want to see which types of vegetation spring up first and which birds return. From what we have seen on the smaller islands we have restored, the transformation will be incredible.”
For more information, read the press release.
Please support this important work by donating today.
Over the last few months, there’s been a slow-boiling battle underway between Holly Dunsworth and Jerry Coyne about the evolution of sexual dimorphism in humans, surrounding the question of why male and female humans, on average, differ in size. The battlefield ranged from blogposts to twitter to magazine articles. In a nutshell, Coyne argued that “sexual dimorphism for body size (difference between men and women) in humans is most likely explained by sexual selection” because “males compete for females, and greater size and strength give males an advantage.” His whole argument was motivated by this notion that certain Leftists ignore facts about the biology of sex differences because of their ideological fears, and are therefore being unscientific.
Dunsworth’s response to Coyne’s position was that “it’s not that Jerry Coyne’s facts aren’t necessarily facts, or whatever. It’s that this point of view is too simple and is obviously biased toward some stories, ignoring others. And this particular one he shares…has been the same old story for a long long time.” Dunsworth went on to propose, seemingly off the cuff, alternative hypotheses for sexual dimorphism in body size in humans that were focussed not on men but on women, as examples of the kind of hypothesis that is relatively rarely considered or tested in this field.
Though on the surface this battle may seem to be about specific biological facts (Coyne certainly tries to win by treating it that way), in reality this disagreement is, as Dunsworth argues, about the process by which hypotheses are tested and about how knowledge comes into existence. About which hypotheses are considered for testing in the first place. As a result, the two ended up arguing past each other quite a bit.
As I followed this whole exchange, I shook my head at the timing–I had a paper in preparation that was SO RELEVANT to the centre of this debate! That paper is now available as a preprint, so I can try to outline why I think that Dunsworth is right, and Coyne is being short-sighted. My argument has *nothing* to do with humans, however–I don’t know the human sexual selection literature well enough to weigh in on that. Instead, my argument is by analogy with our knowledge of mating systems in Anolis lizards.