Care and Propagation
of the Common Monkey Lizard
by Roy Arthur Blodgett
It is important to begin by stating that what follows is largely a work of opinion, informed by the author’s experiences and sometimes by those of fellow keepers who have been willing and generous enough to share their successes and failures. As with all endeavors, there are many ways of achieving success in herpetoculture - and just as many ways of determining what qualifies as success. I don’t claim to know the best way, and want to make it clear that I have no intention of offering the only way. My aim herein is simply to offer what I have observed and what has worked for me, with the driving intention of clarifying how to provide the quality of care and attention which I feel all animals profoundly deserve.
The keeping of animals in captivity is a complicated and often paradoxical prospect; something that I do not expect to entirely reconcile. One thing to me is clear: if I am to be responsible for the well being of a life which is not my own, then I intend to undertake that responsibility with as much care and sensitivity as I can muster. The privilege of this undertaking and arrangement has come with its ample share of gratitude, and occasionally, regret at mistakes I have made. My commitment is to continue learning from both ends of that spectrum, so I may consistently strive to improve as a herpetoculturist.
Introduction and Natural History
Of all the incredible diversity expressed in lizards of the New World, few are as unique and unusual as the monkey lizards of genus Polychrus. Chameleon-like in many aspects - with their slow, deliberate movements, independently moving eyes, and remarkable color-changing abilities - they are distinct among their wild and wonderful counterparts in Central and South America; true oddities, among the odd. Although commonly referred to as monkey anoles or bush anoles, Polychrus represents the only extant genus in the family Polychrotidae, and they are only distantly related to the true anoles of the family Dactyloidae. Of the eight species currently recognized in the genus, the common monkey lizard (Polychrus marmoratus) is by far the most regularly encountered in captivity, and as such will be the focus of this article.
The common monkey lizard (Polychrus marmoratus) is a medium-sized arboreal iguanian lizard, native to lowland Amazonia, distributed from present-day Venezuela, Guyana, Suriname, and French Guiana in the north, west to the eastern slope of the Andes in Colombia, Peru, and Ecuador, and west and south across Brazil. Perhaps unsurprisingly, with such a broad distribution, recent genetic research suggests that the current taxon Polychrus marmoratus is representative of a species complex, with cryptic diversity at play. Given that the vast majority of marmoratus currently kept in herpetoculture are imported from the Guiana Shield region (specifically Guyana and Suriname), we will restrict our focus to this region when referring to the species herein.
One of the author's adult male Polychrus marmoratus.
Common monkey lizards are diurnal, heliophilic, and highly arboreal. They’re most commonly observed within vegetation in forest or forest-edge habitats, but are quite tolerant to disturbed habitats and have even been known to frequent urban gardens and greenspaces. The species is rarely observed on the ground, apart from when laying eggs, but will occasionally descend to lower branches of vegetation, particularly to sleep. They are omnivorous, employing a sit-and-wait hunting strategy, and preying upon a variety of insects and arthropods, including but not limited to katydids, mantids, phasmids, grasshoppers, spiders, and caterpillars. Flowers and fruits, particularly berries, are also consumed with regularity.
Sexual dimorphism is expressed in common monkey lizards by a considerable difference in size between the sexes. Males are much smaller, averaging 20-30 grams, with females often double or triple the size, averaging weights of 50-80 grams. In terms of reproduction, they are generally thought to breed at the onset of the wet season, when resources are most abundant, but are considered capable of breeding year-round when conditions allow. Copulation can last for hours, usually occurring in branches, with the male riding the female’s back and grasping the base of her neck with his mouth. An oviparous species, the common monkey lizard lays an annual clutch averaging from six to ten eggs in number. Larger clutches are not uncommon, especially in larger females of the species.
The sad reality of habitat destruction in Amazonia.
Although Polychrus marmoratus is listed as a species of least concern by the IUCN Red List, and is largely considered tolerant of disturbed habitats, there is no mistaking that their habitat is significantly impacted by human development and resource extraction throughout much of their range. As such, it is worth considering the long term well being of the species, and the potential role of herpetoculture in supporting the conservation of its habitat.
Although the emphasis of this article will be on keeping common monkey lizards under the ideal circumstances of being captive bred and born, the reality as of this writing is that the vast majority of marmoratus available to herpetoculturists today are freshly imported, wild caught individuals. Sadly, very few of the multitudes of monkey lizards imported each year from their native ranges survive quarantine and successfully acclimate in captivity. For this reason, I would feel remiss not to briefly share the protocol I have employed with the handful of wild caught Polychrus which I have successfully acclimated to a life under human care and supervision. I can’t expect that it will work for every individual, but I have been fortunate to lose very few lizards with this approach so far. It must also be noted that the subject of proper quarantine is nuanced and could easily exceed the length of this article. This section is not sufficient as a primer on quarantine in a general sense, but only a brief summary of my acclimation protocol for Polychrus, assuming the basics of quarantine are already known to the reader.
My acclimation protocol is simple, and emphasizes hydration, security, and nutrition, in that sequence. The very first thing I do with a newly arrived monkey lizard in quarantine is remove it from the shipping container and place it into a bucket with a single branch for the lizard to grasp, where I can mist the lizard with lukewarm water and encourage it to drink. More often than not, the lizard will drink heavily, and after a few minutes allowing it to hydrate to its fill, I place the lizard into a basic quarantine setup. My quarantine setups are made from modified translucent plastic storage totes, featuring a sliding glass front door, ventilation grommets, a small heat panel mounted to the lid to provide ambient heat, and a screened section on the lid where a nano halogen and T5 fixture can be placed to create a basking area. I provide a substrate of peat moss or coconut coir mixed with sphagnum moss, some foliage in the form of a live potted plant, and a few branches to allow for basking. I also prefer to have the quarantine setup attached to an automatic misting system, to allow for regular and consistent misting, which greatly supports hydration.
To ensure that the lizard is as secure as reasonably possible in the new environment, I place the quarantine setup in a low traffic area, where disturbances are infrequent, and limit my interactions with the lizard, particularly during the first week. Foliage in the form of live or artificial plants provides camouflage and visual barriers, and is of great benefit in helping the lizards to feel secure and comfortable in their quarantine quarters. Additionally, it can sometimes be helpful to cover some sides of the setup with an opaque material such as paper or cardboard, to reduce visual stimuli.
One of the author's quarantine setups.
After allowing the lizard to settle into quarantine for a day or two, I introduce food. Most Polychrus will feed readily on crickets and other common staple feeders, but occasionally, they need to be enticed to eat with a higher-value prey item, such as a hornworm or silkworm. For particularly stubborn feeders, I have found that phasmids, mantids, katydids, and green grasshoppers provoke the most aggressive feeding response. For this reason, it is particularly helpful to have a variety of feeders at one’s disposal when establishing freshly imported monkey lizards. Once a suitable prey item is found, the keeper can begin to focus on tong-feeding the lizard, and from there, introduce a broader variety of feeders. Quite often, I have employed chain feeding to introduce novel feeders to stubborn monkey lizards. As the lizard chews an acceptable prey item, the keeper can use forceps to hold a secondary feeder up to the lizard’s mouth. Typically, the lizard will seize the secondary feeder as it chews the first and swallow it down. Using this method, I have found that most Polychrus will learn to accept a broader range of prey over time.
The subject of treatment for parasites in imported lizards is a contentious one, and I have typically employed a more conservative, wait-and-see approach, in favor of shotgun treatments. If a monkey lizard is eating, gaining weight, and outwardly healthy in quarantine, I will sometimes forgo parasite treatments, or offer only very minor doses of medication. In the case that a lizard has poor appetite and is losing weight, a more aggressive approach under the expert advice of a veterinarian can sometimes be effective. Unfortunately, because Polychrus are relatively lean and delicate lizards, I have found that the chances of successful acclimation following aggressive parasite treatments is reduced, but occasionally, they can surprise me with their resilience and durability.
Lastly, and importantly, I strictly house monkey lizards individually during quarantine. In a best case scenario, in which an imported monkey lizard does well in quarantine and shows no signs of ill health, I have introduced individuals to my established population after a minimum 90 day quarantine. For some individuals, which express less vigor or signs of poor health, a longer quarantine period should be employed until the lizard expresses better condition for a minimum of 90 days. A quarantine period of 180 days or more is not uncommon, and should be anticipated as a potential requirement for keepers set on introducing wild caught Polychrus to their collections.
Given their highly arboreal habits, Polychrus are best kept in vertically oriented habitats, with abundant branches, foliage, and basking opportunities. In my case, I have typically housed opposite-sexed pairs, or trios of one male and two females, in vivariums measuring approximately 4 feet long by 2 feet deep by 4 feet tall (~120cm by 60cm by 120cm). When housed individually, I have found vivariums measuring a minimum of 2 feet wide by 2 feet deep by 3 feet tall (~60cm by 60cm by 90cm) to be suitable for adult males, and vivariums 3 feet wide by 2 feet deep by 3 feet tall (~90cm by 60cm by 90cm)l to be suitable for adult females. Larger vivariums, whenever possible, are preferred.
Some of the author's 4'x2'x4' (120cm x 60cm x 120cm) vivariums for Polychrus.
The keeper’s climate and reptile room conditions will have a meaningful influence on choosing the most suitable material for the vivarium. In my case, living in a Mediterranean climate in California, and having a reptile room that is difficult to reliably regulate year-round, I use PVC habitats with sliding glass doors, which have the benefit of retaining some heat and humidity to provide a more stable environment within the vivarium. That said, for keepers who live in tropical climates, or who are able to reliably regulate temperature and humidity on the full room scale, screen enclosures might be utilized. Screen enclosures would provide increased airflow and ventilation, which is often beneficial to arboreal herpetofauna. As always, the keeper’s discernment is needed to determine which material most suitably meets the environmental requirements of the species in question. We will explore those requirements in more depth in the next section.
In terms of furnishing the vivarium, a network of stable branches granting access to all areas of the habitat is of greatest importance. Polychrus are highly arboreal and will make use of branches in all orientations, so providing numerous options of vertical, horizontal, and diagonally oriented perches is best. The addition of foliage is useful in providing cover and visual barriers that support the lizards to feel more secure, while also granting the option for them to better regulate their exposure to infrared and ultraviolet radiation. In my case, I have fully planted the vivariums with a variety of vining plants, aroids, and bromeliads, which also help to regulate humidity and air quality. Another unexpected benefit of incorporating live plants was discovered when I realized the lizards also readily consumed the ripe berries produced by one of the vivarium aroids, Anthurium gracile. Although I initially outfitted the branches of the vivariums with cork rounds and other arboreal options for hiding, I found that the lizards never used them and have subsequently relied exclusively on foliage to provide hiding opportunities. Much like chameleons, it is amazing to observe how effectively monkey lizards can disappear among the branches and foliage, even when positioned in plain sight!
Enclosure Plant List
Vriesea splendens (splenriet)
4 parts fine peat moss
3 parts play sand
1 part long fiber sphagnum moss
1 part fine orchid bark
1 part horticultural charcoal
1 part leaf litter
One of the author's 2'x2'x3' (60cm x 60cm x 90cm) vivariums for adult male Polychrus.
Climate Control and Replication
Due to its equatorial latitude, the Guiana Shield which natively harbors Polychrus marmoratus does not express marked seasonal changes in photoperiod and temperature, with a nearly constant 12-hour daylight cycle and average daytime temperatures ranging from 85-90 degrees F (29-32 C) year round. Nighttime temperatures are similarly resolute, averaging 72-75 degrees F (22-24 C) throughout the year. There are significant seasonal rhythms expressed in precipitation, however, with pronounced wet seasons peaking in June and January, interspersed with periods of reduced precipitation. Taking these factors of photoperiod, average temperature, and precipitation into account, and replicating them within the vivarium is an important aspect of marmoratus care and breeding.
In an attempt to provide abundant visible light, ultraviolet radiation, and infrared radiation, as needed by most reptiles to thrive under human supervision, I utilize three types of lighting in my monkey lizard vivariums. Standard PAR38 or PAR30 halogen bulbs heat the vivariums to average ambient temperatures of 78-84 degrees F (25-29 C), while providing a localized basking area exceeding 100 degrees F (38 C). Halogens are particularly useful in emitting near-infrared radiation, allowing the lizards to effectively thermoregulate. Linear high-output T5 bulbs are provided for ultraviolet A+B radiation, creating a gradient of UVI values ranging from 0 to 3.0 among the varying branches. Choosing the right bulb and UV output is primarily dependent on the distance of the bulb from the basking area and can thus vary widely. Lastly, linear LEDs provide bright visible light (~6000K), flooding the enclosures with brightness and nurturing growth in the live plants. In combination, these different types of lighting provide a broad spectrum suitable for the vivarium, and when staged on timers can roughly simulate the sun’s light as it rises, peaks, and sets across the day. Of course, no bulb is a substitute to natural sunlight, which should be provided for monkey lizards whenever feasible.
The above graphs, from Weatherspark, chart the average rainfall and temperatures of interior Suriname. Such data can be used to great effect to inform captive husbandry.
An adult female monkey lizard basking beneath the light bank in the vivarium.
I utilize an automatic misting system to regulate humidity, encourage hydration, and simulate the wet and dry seasons that marmoratus would naturally experience in their native range. Like many lizards from tropical regions, monkey lizards don’t typically drink from bowls or the axils of bromeliads, but prefer to drink droplets that collect on broad-leaved plants, making regular misting essential for appropriate hydration in the species. Such misting also assists in increasing relative humidity, which should be maintained at a minimum of 75%, whenever possible. Furthermore, because the automatic misting system runs on a programmable timer, it is possible for the keeper to simulate the wet and dry seasons by either increasing or reducing the duration and frequency of misting. I prefer to mist the vivariums heavily in the mornings and evenings, with lighter misting in the afternoon.
Diet and Supplementation
Although I’m not aware of any publications or studies which have explored the natural diet of Polychrus marmoratus in depth, it is clear that common monkey lizards fare well under human care on a varied diet of gut-loaded insects and fruit. In my experience, crickets, roaches, grasshoppers, phasmids, katydids, mantids, caterpillars, spiders, flies, fly larvae, and beetle larvae are all accepted prey. Given their passive hunting strategy and relatively slow metabolisms, monkey lizards respond very well to tong feeding, and a strong preference seems to be shown for larger prey. Phasmids, mantids, and caterpillars often provoke the most aggressive feeding response. I have been stunned at times by the impressive size of insects that some Polychrus will devour - in some cases consuming mantids or phasmids comparable in length to the lizard’s own body!
An adult female monkey lizard devouring a mantid.
An adult female monkey lizard consuming berries of the aroid Anthurium gracile in the author's vivarium.
When it comes to fruit, marmoratus show a strong preference for red berries, such as strawberries or raspberries, but have occasionally accepted sliced banana, papaya, mango, and passionfruit. I’ve also infrequently offered bell pepper and various other fruits, with mixed results. Commercial reptile diets, such as those formulated for use with New Caledonian geckos, have been devoured voraciously by some individuals, while others have expressed no interest in them whatsoever. Green vegetation, which can form a large part of the natural diet of the closely related species Polychrus peruvianus, has been largely ignored when offered to the marmoratus in my care. That said, I have observed occasional browsing evidence on vivarium plants, particularly the fresh, newly-forming leaves of Pachira aquatica.
In terms of supplementation, I utilize high-quality multivitamin and calcium products formulated for reptiles to dust feeder insects. My rotation is usually two to three feedings of insects dusted with multivitamin, followed by one dusted with calcium, repeating the rotation and adjusting, as needed. Reproductively active females should be offered additional calcium, as some experiences suggest that female marmoratus are particularly susceptible to hypocalcemia when gravid. Because the monkey lizards in my care are kept under high quality UV-producing bulbs, I avoid supplements with added D3, in an effort to mitigate the potential of hypervitaminosis.
Among herpetoculturists, common monkey lizards have rarely been bred with any consistency in recent years, if ever. This is likely due in large part to the poor condition that most Polychrus express after the ordeal of importation, which has unfortunately granted them the reputation of being delicate and subsequently dismissable as a species worthy of focused attention. That said, I have been encouraged by some minor success breeding the species in the past two years of working with them.
So far, I have successfully managed three clutches, across three attempted pairings of marmoratus. In each case, copulation occurred during my attempts to simulate the wet season, with greater misting frequency, as well as much more frequent offering of food (~3-5 feedings per week), suggesting to me that the species is triggered to breed by a combination of heavy precipitation and resource abundance. In all instances, copulation occurred in the branches of the vivarium (although one pair fell to the ground), with the male pursuing the female, biting the base of her neck, and positioning his tail beneath hers to align cloacas. Each event lasted from one to three hours, with both lizards expressing frequent and nearly psychedelic color changes throughout the process.
Polychrus marmoratus copulation.
When the first female became gravid, I continued with frequent offerings of food, averaging three to five feedings per week. Over the weeks, she became more and more noticeably gravid, displayed by a swollen abdomen and deflated tailbase. In the month prior to oviposition, she refused food, and could often be observed in unusual positions among the branches, seemingly in an attempt to find a more comfortable position and relieve pressure in the abdomen. The days preceding oviposition were characterized by the digging of multiple test holes in search of a suitable nesting site. Finally after 120 days, she began to lay her eggs in a shallow nest at ground level in the vivarium, where the temperature averaged approximately 72 degrees F (~22 C).
Unfortunately, after laying 6 eggs with more to go, the female left the nest and resumed basking. Sensing something was awry, I gently palpated the female’s abdomen to confirm the presence of several more eggs remaining. After visiting the veterinarian and confirming via X-ray that she had 6 eggs left, we ultimately decided to have the remaining eggs surgically removed, with hope that we would be able to save her life. Sadly, it was not to be, and she passed five days after the surgery. I was gutted and filled with regret at the loss. I felt that I had directly contributed to the cause of death by failing to offer an adequate nesting site, despite my best efforts to offer a variety of options. I also concluded that I had been over-feeding the female during gestation, given the rather large clutch she was carrying of 12 eggs, which further exacerbated the issue.
My first clutch of marmoratus eggs, midway through incubation.
With the next two gravid females, I took a different approach, limiting feeding to only twice per week. I also redesigned the vivariums, adding elevated planters, which I thought might offer a nesting option of a higher temperature along the vivarium’s thermal gradient. In both cases, the females were much less noticeably gravid, given the leaner feeding regimen. Both also exhibited standard behavior until the final weeks before oviposition, when they refused food and began to show restless behavior. At 94 and 95 days after observed copulation, respectively, the second and third females chose to nest in the elevated planter, excavating shallow nests among the plant roots and laying clutches of 6 and 8 perfect eggs. The surface temperature at the elevated nest site was ~80 degrees F (~26.5 C), when measured with an infrared temperature gun.
A clutch of marmoratus eggs in the nest.
Note the unusual longitudinally-grooved texture of the eggs.
All three clutches were removed from the vivarium to be placed in an incubator. The first clutch of six eggs was incubated on clay substrate at a temperature of 78 degrees F (25.5 C), with a nightly drop to 76.5 degrees F (24.7 C). Over the course of incubation the eggs swelled considerably and after 160 days, three robust, healthy hatchlings emerged. The remaining three eggs were cut after 162 days to reveal fully-formed, but drowned neonates. With the following two clutches, I made some adjustments, hoping for a better hatching outcome, placing the eggs on elevated egg trays over the substrate, with some damp moss over the top of them in the incubation container. I also adjusted the incubation temperature to 80 degrees F (26.6 C), with a nightly drop to 78.5 degrees F (25.8). After 145 days the second clutch hatched, with all six neonates hatching successfully, and after 158 days the third clutch hatched, with all eight neonates hatching successfully - a far more acceptable outcome!
Neonate marmoratus in the incubation container.
Always a welcome sight!
Rearing of Neonates
I’ve found that, in most respects, the care of neonate monkey lizards departs very little from the care of the adults. Most are born with ravenous appetites, and readily take to feeding on appropriately sized insects. Flightless fruit flies, bean beetles, small caterpillars, buffalo beetle larvae (Alphitobius diaperinus), roach nymphs, and small crickets are all accepted prey, in my experience. Neonates and juvenile Polychrus are also often particularly fond of commercial reptile diets, which can be offered on a small spoon. I typically feed neonates and juvenile monkey lizards 4 to 5 times each week, and they grow steadily, but not at a particularly fast pace, with the growth of females consistently outpacing the growth of males.
I have experimented with housing the neonates both individually and communally, with a slight preference for the former, particularly in the first weeks after hatching, and again as the lizards approach sexual maturity, when males will begin to show signs of territoriality and aggression. When housed communally, some individuals tend to establish themselves as being more confident and bold, and will sometimes bully the smaller, meeker ones. Outright aggression, such as biting and chasing, is uncommon, but subtle signs of bullying can be detected by observing the subordinate lizard hiding an unusual amount, or otherwise appearing listless or depressed. In such cases, I find it is best to separate the lizards and monitor them closely.
Neonate monkey lizards are incredibly adorable and can become remarkably tame.
Fortunately, I can attest that even as neonates, captive bred and born monkey lizards exhibit few of the issues seen in wild caught, imported Polychrus. They are quick to catch on to feeding routines, and will often become excited at the approach of the keeper; even learning to hand feed within weeks of hatching. I’m happy to say that of all which have hatched here so far, none have failed to thrive and all have proven to be surprisingly resilient.
Lingering Issues and Unanswered Questions
Though I am optimistic about the potential of Polychrus marmoratus to become established in herpetoculture at a broader scale, there remain some lingering issues and unanswered questions that should be addressed, in order to paint a clearer picture of the species’ long term viability within the practice.
One question that springs to mind is whether individual housing or cohabitation is better suited to success with the species. Although Polychrus are rarely aggressive toward conspecifics of the opposite sex, and the majority of keepers house them in groups, I’m not convinced that they are best kept in cohabitation. In my experience, when kept in 1.2 trios, a subtle hierarchy will form, with the largest female usually assuming the role of the dominance. In this scenario, the subordinate female can occasionally be bullied by the dominant one, sometimes to the extent of forcing the subordinate female to spend most of her time in the lower reaches of the vivarium, losing access to valuable basking, thermoregulation, and food resources. A similar issue can arise during the peak of breeding season, when males can become extremely persistent with their amorous advances, causing the females to avoid the prime areas of the vivarium in an effort to hide from the male. To address these issues, I prefer to have the option of separating the lizards when necessary, and have kept a vacant vivarium available to allow for this. These issues may also resolve themselves in a sufficiently spacious vivarium - though the space would have to be much larger than most keepers would consider feasible. With all of this in mind, it may ultimately be better for all involved to simply house the lizards individually, except in the instance of breeding introductions. More experimentation, adaptation, and observation will be necessary to determine what is best in the long term.
Perhaps of greatest concern is the issue of reproductive health among female monkey lizards. As detailed in the ‘Breeding’ section previously in this article, I have encountered some issues related to dystocia and potential hypocalcemia with reproductively active female Polychrus. Worryingly, the exact causes of these issues at this time are largely speculative, and warrant much more experimentation and observation to determine the best course of action for supporting gravid female Polychrus to successfully lay their eggs and recover from the process. That said, my initial thoughts are to ensure that gravid females are not over-conditioned, receive plenty of calcium supplementation, and are kept individually to avoid undue stress from conspecifics. Furthermore, it seems particularly important to offer a variety of nesting site options across a broad thermal gradient, until we can better understand their ideal nesting preferences.
All things considered, these issues and questions do little to deter me from believing in the potential of Polychrus marmoratus to succeed in herpetoculture long term. I feel optimistic that with time, adaptation, and further observation, the ideal protocols for keeping these enigmatic lizards will be better illuminated and subsequently refined, as has been the case for so many other species across the span of herpetoculture.
The common monkey lizard has been one of the most rewarding species I have kept as a herpetoculturist. Their grace, beauty, and inquisitiveness make them an excellent lizard for display, and I’m always delighted to walk into the reptile room and see them basking among the branches in their vivariums. Even more, I’ve found that some individuals become surprisingly outgoing, willingly approaching me or leaping out onto my shoulder, hoping to be offered an insect or slice of fruit - an unexpected outcome for such a seemingly vigilant species.
Though wild caught specimens can present challenges, I have found that captive bred offspring are hardy and relatively forgiving. With continued focus and dedication among capable keepers, I’m optimistic about this species’ potential to have a lasting place in herpetoculture. They are certainly worthy of the effort and attention.
I would be remiss not to extend special gratitude to Kaleb Hill and Florian Wagner, whose experiences and successes keeping Polychrus I’ve been fortunate to learn from and build upon. Danny Craig, James Hicks, and Fritz Meyer, among others, have also offered valuable insights. Additionally, I am grateful to the many keepers, scientists, and enthusiasts who have contributed to the Polychrus Husbandry Working Group on Facebook. Hopefully, together and in due time, we will continue to demystify these fascinating lizards and establish them in herpetoculture, so future generations may enjoy them for many years to come.
References and Recommended Reading
Behavior, habitat, diet and reproduction of the iguanid lizard Polychrus acutirostris in the caatinga of northeastern Brazil.