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!
During an excursion with Indigo Expeditions to Estación Biológica Las Guacamayas, Parque Nacional Laguna del Tigre, Guatemala, we observed the unusual behaviour of a female Lichen Anole Anolis beckeri (previously Anolis/Norops pentaprion), a rarely-studied, canopy-dwelling, anole from Central America. In a paper in Mesoamerican Herpetology, we report on observing a female A. beckeri potentially tending and guarding eggs. This is possibly also an example of oviposition site fidelity in an anole.
Seven unknown lizard eggs were first discovered on 9th July 2015. The eggs were deposited in the leaves of a bromeliad plant (Bromelia sp.) roughly 5m above the ground. The lichen anole is typically a canopy-dwelling species but, luckily for us, the bromeliad was in a tree at eye level to one of the research station’s balconies! The bromeliad plant had collected water and one egg in particular, lying partially submerged, was a brown, speckled colour. Another of the eggs appeared indented, a sign of potential imminent hatching. The female A. beckeri deposited an additional egg after our return to the UK, which reflects similar egg laying pattern for Anolis where independent, single eggs are laid every 5–25 days during the breeding season (Losos, 2009).
Over the next few days there were no changes in the eggs’ shapes or colour. It wasn’t until 3 days later, on the 12th of July, that we finally witnessed the owner of these eggs: a female A. beckeri sat above the clutch on one of the fronds of the bromeliad. The anole was seen repeatedly climbing into the bromeliad, seemingly to examine the eggs. She would then lick them and exhale heavily over them (perhaps to increase airflow?), before retreating to the top of the bromeliad. She repeated this sequence of behaviours, retreating to safety up the tree and then re-emerging to check on the eggs numerous times.
We recorded these behaviours on video and in photographs from a distance, to avoid disturbing the lizard. The female returned on numerous occasions to examine, lick and ‘aerate’ the eggs or to seemingly guard the eggs over the next few days but on the 14th of July the female only monitored the eggs from a distance of ca. 30 cm away and did not approach them.
We also witnessed potential predatory behaviour from a Mexican Parrot Snake (Leptophis mexicanus), On the 15th July the snake was seen in the vicinity of the clutch, perhaps attempting to prey on the adult female. See full paper for detail.
These observations offer insight into the life history and behaviour of this rarely-seen anole species. Hopefully, with the continued work of Indigo Expeditions and the guides at Estación Biológica Las Guacamayas we’ll learn more about these interesting reproductive behaviours in the future.
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 email@example.com
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. Continue reading Dewlap Design Facilitates Recognition But Not Detection: a Field Test Using Robots
In the most recent issue of Herp Review, Anole Annals stalwarts Kevin de Queiroz and Jonathan Losos documented their account of observing an adult female grass-bush anole (Anolis pulchellus) consume a dwarf gecko (Sphaerodactylus macrolepis) on Guana Island, British Virgin Islands. The authors share their detailed report below:
Many primarily insectivorous lizards will eat other vertebrates on occasion, a behavior that has been reported in many species of Anolis. One unifying generality is that such carnivory is size structured, with the predator usually being substantially larger than the prey (Gerber 1999. In Losos and Leal [eds.], Anolis Newsletter V, pp. 28–39. Washington University, Saint Louis, Missouri). Not surprisingly, reports of anole carnivory pertain primarily to middle-sized and larger anoles. Here we report carnivory by a small anole of the species A. pulchellus. To our knowledge, this is the first instance of carnivory reported for this species and one of few for any similar-sized anole (the record noted by Henderson and Powell 2009. Natural History of West Indian Reptiles and Amphibians. University Press of Florida, Gainesville, Florida. 495 pp. is based on the observations reported here).
We observed a female A. pulchellus (SVL ca. 38 mm) capture and consume a Sphaerodactylus macrolepis (SVL ca.18 mm) in the leaf litter at approximately 1430 h on 25 September 2006, on Guana Island, British Virgin Islands, near the head of the Liao Wei Ping Trail at roughly 18.47916°N, 64.57444°W (WGS 84). The anole jumped from a low perch (ca. 20 cm above the ground) to the ground and bit the gecko, which escaped and fled 15–20 cm to the opening of an ant nest. The anole attacked the gecko again, seized it in its mouth and carried it approximately 10 cm up a vine, a distance of 15–20 cm from the site of attack. Initially, the anole held the gecko upside down (i.e., dorsal surface facing down), biting it between the fore and hind limbs on the left side. Eventually the anole worked its grasp posterior to the base of the tail, still on the left side. At this point, parts of both the base of the tail and the left hind limb were in the anole’s mouth (Fig. 1). The anole then manipulated the gecko so that it was no longer upside down, but rotated about its long axis by roughly 90 degrees (the ventral surface of the gecko was then oriented forward relative to the anole) at which point it was biting the gecko at the base of the tail and possibly by the left hind limb; the anole eventually manipulated the gecko so that it held it tail-first in its mouth, dorsal side up, at which point the anole proceeded to ingest the gecko tail first (during this time, the tail itself broke off and was carried away by ants, which had been biting the gecko in several places since shortly after it was
captured by the anole). Total time from capture to complete ingestion was approximately five minutes.
Predation on Sphaerodactylus geckos has been reported in anoles of only a few species, none of which are as small as Anolis pulchellus (Henderson and Powell 2009. Natural History of West Indian Reptiles and Amphibians. University Press of Florida, Gainesville, Florida. 495 pp.). However, given the size discrepancy between the lizards in these two clades and their extensive coexistence across the Caribbean, we suspect that such interactions may occur with some frequency. Moreover, the high population densities of some Sphaerodactylus geckos (e.g., Rodda et al. 2001. J. Trop. Ecol. 17:331–338) and the diurnal activity of several species (Allen and Powell 2014. Herpetol. Conserv. Biol. 9:590–600) suggest that they may be important prey items for anoles.
– Allen, K.E. and Powell, R., 2014. Thermal biology and microhabitat use in Puerto Rican eyespot geckos (Sphaerodactylus macrolepis macrolepis). Herpetological Conservation and Biology, 9(3), pp.590-600.
– Gerber 1999. In Losos and Leal [eds.], Anolis Newsletter V, pp. 28–39. Washington University, Saint Louis, Missouri
– Henderson and Powell 2009. Natural History of West Indian Reptiles and Amphibians. University Press of Florida, Gainesville, Florida. 495 pp.
– Rodda, G.H., Perry, G.A.D., Rondeau, R.J. and Lazell, J., 2001. The densest terrestrial vertebrate. Journal of Tropical Ecology, 17(02), pp.331-338.
Walking down “Red Road” in Pinecrest neighborhood of Miami, FL, it is hard to miss a myriad of lizards on trees and street lamps. Among the many city-dwelling residents, the Cuban brown anole (A. sagrei) and the Puerto Rican crested anole (A. cristatellus) are seen virtually everywhere. While there is evidence that anoles are adapting to urban landscapes, most past studies have focused on adult stages (Kolbe et al., 2012; Winchell et al., 2016; Lapiedra et al., 2017) and early life stages have been largely ignored. Our recently published study in the Journal of Thermal Biology (Tiatragul et al., 2017) was the first to address how anole embryos could facilitate establishment of populations in cities.
The transformation of natural habitats into urban landscapes dramatically alters thermal environments, which in turn, can impact local biota. For ectothermic organisms that are oviparous (like anoles), developing embryos are particularly sensitive to these altered environments because they cannot behaviorally thermoregulate and are largely left to the mercy of their surrounding environment. Yet, we know little about how thermal environments in urban and forested areas affect embryo development and hatchling phenotypes.
To determine if embryos from urban and forested sites are adapted to their respective thermal environments, we incubated eggs with temperature regimes that mimic likely nest conditions in both urban and forested environments. Our results show that for two species (A. sagrei and A cristatellus), urban thermal environments accelerated development, but had no impact on egg survival or any hatchling phenotypic traits measured (including body size, running performance, and locomotor behavior). Furthermore, there is no evidence that embryos from either habitat are adapted to their respective thermal environments. Rather, this lack of major effects suggests that both anole species are physiologically robust to novel environments. This may explain their success in establishing populations in human-modified landscapes.
Physiological adaptation by embryos are not required for a population to establish successfully. Maternal behaviors, like maternal nest site selection could shield embryos from lethal conditions. Hence, our next study is going to involve quantifying maternally selected nest sites in the urban and forested landscapes.
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.
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.
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.
I’m back from Redonda and the expedition was a great success! I’m happy to report there were many Anolis nubilus boulder-hopping out of the way of the black rats and even blacker ground lizards on the island. In many ways the trip was even more challenging than expected but we came out with quite a lot of data so we have a great sense of the current status of the reptiles on the island and a baseline for comparisons into the future. I have even more stories and some videos going up on my blog to keep watch over there if you want even more details about Redonda.
To refresh your memories, Redonda is an island of Antigua and Barbuda and was completely denuded by rats and goats over the last century. Despite the dearth of vegetation, three endemic reptiles had been hanging on: Anolis nubilus, Ameiva (Pholidoscelis) atrata, and an as-yet unnamed Sphaerodactylus dwarf gecko. The government of Antigua and Barbuda, in collaboration with Fauna & Flora International and local NGO the Environmental Awareness Group, has decided to undertake a massive restoration effort by eradicating the rats and relocating the goats. My job was to get some baseline data on the current lizard populations so we can figure out how they change into the future.
Helicoptering to the island was every bit as exciting as I’d hoped. The Jurassic Park theme was playing through my head the whole way down. See that grassy patch with slightly fewer large rocks – that was the little tiny helipad, but our pilot was a pro and set us down perfectly. Almost as soon as we were out of the helicopter, we deposited our bags by our tents and set about catching Anoles.
Anolis nubilus is at first blush a relatively innocuous member of the genus. They’re perfectly camouflaged in this environment, which is to say they’re drab gray and brown. Their dewlaps are cream-colored (which is really just my nice way to say drab gray-yellow) and the most decorated of the females sport faint dorsal stripes. Males did fairly regularly display impressive crests behind their heads, but nonetheless, the species at first and second glance is considerably less flashy than many of their cousins on nearby islands.
All that said, there’s still a lot of cool stuff going on with nubilus. As Skip mentioned in his article 45 years ago, there’s a casuarina tree right next to the remains of the mine manager’s house that hosts an abundance of the few Redonda tree lizards living up to their name. The tree is still there and the lizards are still eagerly defending their precious few branches (see above).
There are actually quite a few trees still on Redonda, some of which are native Ficus trees. For the most part they’re in fairly inaccessible areas, but that really just means you need to bring a longer noose pole and don’t look down. I caught a lizard on this tree below with a perch height of approximately 350 meters (that’s really going to mess with the averages). Truth be told, after catching the lizard my knees were so wobbly I had to go find a nice big boulder and just had Geoff and Anthony shout me data for a while.
After a week on the island and many, many Anoles, we got morphometric and performance data, diet data, extended focal-animal behavior videos, two mark-recapture density studies and two permanent transects established, thermal ecology data, habitat use data, and flight behavior data. We even exhaustively determined whether nubilus likes Chuckles! (But that’s a story for another post).
I know this is an Anole blog, but there were some pretty cool things going on with the other reptiles on the island, too. The ground lizards were jet black and really big. Here’s a picture of Anthony Herrel trying to get a tail measurement:
The atrata spent their days cruising around scavenging. We saw one eating a hermit crab, and we heard rumor of another that managed to get a sardine away from one of the crew working on the eradication effort! Analyzing the stomach contents of these guys is going to take quite a lot of detective work.
We also were able to gather the first natural history data on this unnamed dwarf gecko species. They’re strangely beautiful with an unlovely shovel-face and semi-transparent, too-squishy, gelatinous body. You wouldn’t guess it but they’re quick!
In all, the reptiles of Redonda were fascinating and getting to explore the island was a unique privilege. I can hardly wait to return next year, and many years after, to see how the lizards change with the island.
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.
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.
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 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 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.
“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.”
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.
I am a biology Student from Switzerland and together with my travel mate Demian, I visited Cuba for 3.5 weeks in January and February 2017. We are birders, but pretty much interested in everything that moves! We were taking pictures of lizards whenever we could, but without specifically looking for them. Back home, I was surprised how difficult the identification can be and so I would be happy if you can confirm, correct or help me with the ID. There are a lot of pictures…
I will report every safely identified lizard, probably with observado.org, together with the name of the expert, who is helping us out.
We will also put a comprehensive trip report on cloudbirders, including the herp list.
It’s currently dewlapping mayhem down here at the moment, with all species except the late-rising Cuban knight anoles (A. equestris) out and showing off!
Visual displays such as dewlap extensions are often used to mediate physical interactions by acting as an indication of the relative size, strength, and fitness of each individual. This is beneficial for both parties; dominant individuals do not have to waste energy that a physical interaction would require, and weaker individuals avert the risk of physical injury (of course, both reasons are reciprocal to both individuals also).
However, when two individuals cannot determine dominance through visual communication, for example if two individuals are equally matched in size, then an aggressive and physical confrontation may occur (read a previous account of one such interaction between two equally-sized males here). The results of these interactions are apparent in many injurious forms, for example through extensive bite marks to the body (as previously discussed here and here), or perhaps even to the extent of tail loss (as discussed here).
Yesterday (9 March 2017) I observed this male Puerto Rican crested anole (A. cristatellus) below that looks like another male had taken a good bite at him!
Of course, there are many avenues through which such an injury may appear. However, the presence of a still-erect nuchal crest paired with how fresh the wound looks (and the time of year!) gives me the impression that this was probably the result of an intraspecific male-male interaction.
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Foraging behavior reflects a trade-off between the benefits of obtaining vital resources and the potential costs of energy expenditure, missed mating opportunities, and predation. Through time, selection should canalize foraging behaviors that optimize fitness within a given environment, but novel habitats, like urban landscapes, may require behavior to change. For example, human-landscape modification often results in significant reductions in structural complexity of habitat as compared to natural areas, potentially leaving individuals with a greater sense of perceived vulnerability as they venture out to feed. Moreover, these landscapes can alter the diversity and density of predators in ways that might leave prey with a greater sense of perceived predation risk.
In a recent paper in Urban Ecosystems, Chejanovski et al (2017) sought to quantify differences in foraging behavior between anoles from urban areas and those from more natural, forested locations. They utilized two trunk-ground anoles: Anolis sagrei in Florida and A. cristatellus in Puerto Rico. In both urban and natural habitats, they located male lizards in survey posture (Fig 1), which indicates an individual is likely searching for food, and placed a tray with mealworms on the ground at a fixed distance from the perch. They measured each lizard’s latency to feed which was the time it took to the lizard to descend from its perch and capture a mealworm.
Because the availability of complex habitat structure and the proximity of predators might both influence foraging behavior, they experimentally manipulated perch availability for A. sagrei and predator presence for A. cristatellus in both urban and natural habitats. For A. sagrei, they provided half the individuals with two extra perches between the lizard’s original position and the food tray. For A. cristatellus, they manipulated perceived predation risk by placing a static bird model on the opposite side of the feeding tray from half the lizards.
Additionally, they measured several other factors that might influence foraging behavior: the number of available perches within a fixed radius of each lizard – increased habitat complexity might result in lower perceived predation risk; perch height of each individual – those that perch lower to the ground may be more motivated to feed and those that perch higher may be satiated; estimates of body temperature by placing a copper model at the original position of each lizard – body temperature can influence locomotor function and this may have consequences for how easily a lizard can escape predation and play a role in its perceived risk. They also measured the density of conspecifics in the immediate vicinity and noted when conspecific individuals captured mealworms from the feeding tray.
Finally, they measured SVL and mass for a representative sample of each population (urban and natural) in order to calculate body condition. Trade-offs between costs and benefits of foraging decisions can be influenced by satiation of hunger, and body condition, which increases with food consumption, may indicate the extent to which individuals are well-fed.
For both species, lizards from urban areas had a longer latency to feed and demonstrated lower overall response rates to food trays; many individuals never attempted to capture a mealworm in the allotted time (20 minutes). For A. sagrei, habitat (urban vs. natural) best explained feeding latency, but perch height and the presence of conspecifics were also important determinants of feeding latency for A. cristatellus. Individuals perching lower had shorter latency, and latency was shorter when a conspecific attempted to feed from the tray. Neither experimental perch availability nor perceived predation risk (bird model) had any influence on foraging behavior. In both species, individuals from the forest were smaller (SVL) and less massive than those from the city. Body condition was higher for urban A. sagrei but did not differ between natural and urban habitats for A. cristatellus.
Because of the reduced availability of perches and structural complexity in urban habitats, urban lizards could have generally higher perceived predation risk and this might explain their reluctance to feed; however, experimental perch availability did not influence foraging behavior for A. sagrei and an artificial predator had no effect on A. cristatellis. The latter may simply reflect that the experimental predator was stationary and a moving predator may have elicited different results.
It is possible that foraging differences reflect food availability in urban vs natural habitats, and thus motivation to forage. Urban anoles had higher body condition and may be generally better fed than those from the forest; however, the authors found no significant correlation between individual body condition and latency to feed. It is also possible that mealworms represent a novel food source for urban anoles, and this resulted in a hesitance to initiate feeding since many animals are reluctant to approach novel objects/ food (neophobia).
In summary, this study demonstrates that differences do exist in foraging behavior for two distantly related species of anoles between urban and forested habitats. The increased latency to feed observed in urban anoles could be due to perceived predation risk, foraging motivation, neophobia, or some combination. What is left to be determined is the extent to which these behavioral differences might be adaptive in their respective habitats.
As part of some ongoing work comparing muscle physiology and performance among Anolis species, I am in search of data on the Field Active Body Temperature (Tb) of Anolis chlorocyanus so that I am sure to perform data collection at relevant temperatures. Unfortunately I have been unable to locate Tb data for this species in the literature, so I hoped one of you might have this information and be willing to share it with me. Any help would be greatly appreciated!
Along with Devi Stuart-Fox, Indraneil Das and Terry Ord, I recently published a paper in Biology Letters showing that arboreal Draco sumatranus lizards orient themselves on the tree trunk perpendicular to the position of the sun during broadcast signalling. This presumably increases the radiance of the translucent dewlap, and likely it’s conspicuousness.
Draco lizards are ecologically analogous to the anoles and share similar signalling behaviour (see this recent Draco clip from the BBC’s Planet Earth II). They too possess extendable dewlaps that differ in colour and size between sex / species groups, and they also live in many different habitat types throughout Southeast Asia. I’ve written about my Draco research on Anole Annals before, here and here, if you’re interested – I hope they’re now well accepted as honorary anoles!
Like the anoles, the skin of the dewlap for many Draco species is stretched thin when extended and allows light to pass through. Leo Fleishman published a Functional Ecology paper in 2015 measuring how the dewlap of Anolis lineatopis appears to glow when positioned with the sun behind them, and how this might improve signalling efficacy. Contrary to expectation, they found the transmission of light through the dewlap doesn’t improve the luminance contrast of the dewlap against the background. The radiance of the dewlap is increased by light transmission (radiance is the sum of the light reflected by the dewlap and any transmitted through the dewlap) – but patches of high radiance are very common in Anolis lineatopis forest shade environment, due to many the little shafts of light shining between gaps in the leaves. Instead they showed that due to the higher total intensity of the dewlap colour (thanks to light transmission) it’s probably easier for a conspecific to discriminate the signal from the natural background colours.
Given this and the similarity between anole and Draco dewlaps, I wondered whether Draco lizards might behaviourally adapt their position on the trunk relative to the position of the sun, to maximise the exposure of the extended dewlap to sunlight. To look at this, I just observed the position of the lizard relative to the sun upon first sighting, and noted whether the lizard was displaying, and if so, whether was it directly to a neighbouring conspecific, or whether it was a territorial broadcast display. We found males were significantly more likely to be oriented perpendicular to the sun when displaying, but not when not displaying (fig. 1).
Of course, signals intended for specific individuals in close-range encounters require the signaller to position themselves such that the receiver is in line of sight – but Draco lizards (and anoles) also give these ‘broadcast signals’ which are not intended for any specific individual, but just as territorial display. For these signals, where there is not another lizard around, they seem to orient themselves perpendicular to the sun, so their extended dewlap is exposed to the most light.
Female D. sumatranus also have dewlaps, but they are small in size and females only very occasionally engage in broadcast display. I had not expected to see this orientation behaviour in females, as their dewlaps appear opaque and so don’t benefit from light transmission. However, I found the same orientation pattern for females as for males: perpendicular to the sun when displaying, but not when not displaying. This is perhaps because their dewlap reflects UV light (fig. 2) and direct sunlight is richer in UV and shorter wavelengths than light reflected off objects in the surrounding scene. Males have yellow dewlaps, and they too reflect a little UV (though much less than females). Of course, the transmission of light is unidirectional and only increases the radiance of the dewlap for those viewing the dewlap from the opposite side to that of illumination, so the benefit of direct sunlight hitting the UV/yellow male dewlap likely plays a role in this orientation behaviour for males as well.