That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

The green anole has long been a pet trade staple, but these active, attractively-colored little lizards have quite an interesting natural history as well. Today we’ll take a look at how they live and cope with people, and point out some of their special traits. Next week I’ll cover their care in captivity. Classification

Family Iguanidae, Subfamily Polytrotinae.

Note: some authorities have reclassified certain Anolis species as Norops.

At least 370 anole species range throughout southern North America, Central America, South America and the Caribbean. All are fairly small, slender, egg-laying lizards. Males possess a large, colorful throat fan (dewlap) that is used in territorial displays and other forms of communication; depending upon the species, the female’s dewlap is smaller or vestigial.

The foot pads of most are equipped with lamellae (please see below) to assist in climbing. Nearly all are arboreal, with the tails of the “bush anoles” (Genus Polychrus) being prehensile. Several species, however (i.e. Genus Pristidactylus), are largely terrestrial.

Anoles feed mainly upon insects, spiders and other invertebrates. Several species have been observed to lap nectar and sap, and the Puerto Rican anole (A. cristatellus wileyae) sometimes consumes fruit.

The green anole is the only species native to the USA, although a number of others have been introduced here (please see below). The green anole population in southwestern Florida has recently been designated as a distinct subspecies, the pale-throated green anole, A. carolinensis seminolus.

Physical Description

The green anole is slenderly built, possessed of a long tail, and reaches 6 -7.5 inches in length. The color of each individual varies from light and dark brown to pale and bright green (please see below).

Males are larger and stockier than females and have a thicker tail base and a wider, more colorful dewlap (throat fan). The dewlap of the male is pink to pale red in color (white or cream-colored in A. c. seminolus), and is vestigial or absent in females.

Anoles clad in various shades of blue are sometimes available in the pet trade. Arising from a genetic mutation, they are quite striking.

Range

Green anoles are found from southern North Carolina west to eastern Texas and southeastern Oklahoma and south to the Florida Keys. They also live in the Bahamas, Grand Cayman Islands, Anguilla and Cuba. There are disjunct populations in Mexico.

Green anoles have been introduced to Belize, southern Japan and Hawaii, and have established breeding populations in those areas.

Habitat

Woodland edges, pine-palmetto scrub, cypress swamps, open forests, overgrown fields, farms, parks, backyards and gardens; highly arboreal.

Status in the Wild

Green anoles adapt well to some human disturbance and may even be drawn to gardens by high insect populations and the humidity generated by frequent plant-watering. They are, however, declining across parts of their range due to over-collection and to the effects of introduced Anolis species that occupy the same habitats and compete with (the brown anole) or prey upon (the knight anole) them.

Diet

Caterpillars, tree crickets, grasshoppers, flies, beetles, moths, ants, roaches, spiders and other invertebrates; they occasionally lap over-ripe fruit, nectar and sap.

Reproduction

The breeding season extends from April to September, although it is shorter in the northern part of the range. Males are highly territorial and battle interlopers. The male’s courtship display consists of vigorous head-bobbing with continued extensions of the dewlap. The dewlap reflects ultraviolet light and is perceived by the female as brilliantly colored.

Males chase females about and grasp them behind the neck during copulation. The first eggs, 1-2 in number, are laid 2-4 weeks after mating occurs. They may be buried in soil or secreted below leaf litter or even left the surface, along a log or other structure. Eggs are sometimes deposited in substrate that has accumulated among air plants or in tree knot-holes above-ground. Additional clutches of 1-2 eggs are laid throughout the breeding season, to a total of 8-10 eggs per female. The eggs hatch in 30-45 days.

 

The 1,200+ skink species form the largest lizard family, Scincidae, and among them we find quite a number of unusual animals. Yet the prehensile-tailed skink manages to distinguish itself as unique in not one, but many ways.Largely unknown in the pet trade until the late 1980’s, these arboreal skinks became widely available when logging in the Solomon Islands brought their formerly inaccessible treetop homes crashing to the ground, and left the lizards in reach of collectors. I and others noticed right away that they were quite different than anything we had run across previously.

A Highly Social Lizard
The limited field studies suggest, and our captive observations support, that prehensile-tailed skinks live in hierarchal colonies (a reptilian social group is known as a circulus) and exhibit a variety of highly-developed social behaviors. Group members seem to recognize one another by scent, and mark their territories with waxy secretions. Although often found in pairs, up to 10 individuals have been collected from a single tree hollow, but the functioning of these groups is not understood.

A Placenta and a Giant Offspring
Females, which average 24 inches in length, have a true placenta. They produce 1, rarely 2, huge (to 13 inches) offspring after an amazingly long gestation period of 6 – 8 months. Esteemed veterinarian and herpetologist Dr. Kevin Wright has likened this feat to that of a woman giving birth to a 6 year old child!

Complex Parental Care
The young stay close to their mothers for some time and the females become very aggressive towards people and other skinks after giving birth. Although we do not as yet understand the interactions between adults and young, it is quite clear that those reared in isolation exhibit, if you will, “anti-social” behavior (they are noticeably more aggressive than other skinks, to the point of charging people opening the door of their cages).

Coprophagy (eating of feces) is common, and some believe that this provides the young with important intestinal flora. Breeding occurs year round in the wild and captivity. The young begin feeding at about 10 days of age, and reach sexual maturity in 10 months to 1 year.

Much More to Learn
All told, a strange and fascinating beast. Although captive longevities approach 25 years, we have yet to scratch the surface when it come to understanding prehensile-tailed skink social interactions.

The American Association of Zookeepers has posted an informative article on this species’ fascinating social structure at:
http://www.aazk.org/forum/viewtopic.php?pid=1320

A newly discovered bacteria species (Deviriesea agamarum) is responsible for a variety of fatal organ diseases that currently plague captive lizard populations, according to an article in the September, 2008 issue of The International Journal of Systematic and Evolutionary Microbiology. Particularly hard-hit has been a breeding program for the highly endangered Oman dab lizard, Uromastyx thomasi, but a number of other desert-dwelling lizards in the genera Uromastyx and Agama are susceptible as well. The bacterium is related to others that cause human skin infections.The identification of the bacterium has important implications not only for the treatment of disease in captive lizards, but also for wild populations. Captive-bred reptiles that are used in reintroduction programs may appear healthy but harbor diseases that can decimate wild populations. Some years ago, this very situation caused serious respiratory disease outbreaks among desert tortoise populations in the American southwest, and led to a ban on the release of confiscated tortoises. Similarly, the September 23, 2008 issue of Current Biology states that many amphibian species in Europe are currently threatened by a fatal Chytrid fungus that was introduced to the wild by Mallorcan midwife toads released as part of a reintroduction effort.

You can read more about disease problems that affect reintroduction programs at:
http://esciencenews.com/articles/2008/09/22/captive.breeding.introduced.infectious.disease.mallorcan.amphibians.0

Click: The Monitor Lizards (Family Varanidae) – Family Overview and Species Accounts; – Some Interesting Monitors and Their Care – Part I, to read the first part of this article.

Merten’s Water Monitor, Varanus mertensi
The popularity of this most aquatic of the world’s monitor lizards is soaring, and with good reason – it is active, hardy, of manageable size (averages 3 feet in length, occasionally to 4) and very responsive to its surroundings.

Range
Native to northern and western Australia (Northern Territory, Queensland, South Australia and off-shore islands), Merten’s water monitors frequent creeks, rivers, canals, ponds and reservoirs. They bask on the shore or low overhanging branches, and rarely stray far from the water’s edge. Although common at present, this situation may change – water monitors readily consume introduced marine toads, and many are killed by the amphibians’ toxins.

Unique Adaptations
Merten’s water monitors, named after eminent Russian-born herpetologist Robert Mertens (1894-1975) of Frankfurt Germany’s Seckenberg Museum,
are deep brown to black in color, with dark-edged cream or yellow spots. The tail is laterally compressed and the nostrils, which can be sealed during dives, are located high on the snout.

Housing
Water monitors require a spacious cage (at least 4’x4’x 3′), a UVB source and a large (preferably drainable) pool. They must be able to bask at 90-95 F and to dry off completely upon leaving the water.

Diet
The natural diet consists largely of crabs, crayfish and fish, but frogs, tadpoles, turtle and other reptile eggs, shrimp, snails, nestling birds, planigales and other small mammals, large insects and carrion are also taken. They have been observed foraging in dumps, with discarded sausages apparently being a favored food! Water monitors use their tails to concentrate small fishes when hunting in the shallows.

Captives should not be fed a rodent-based diet, but rather one weighed heavily in favor of whole, fresh-water fish, whole, unshelled prawn, crayfish, roaches, crickets, earthworms, and canned insects/monitor diets . Pink mice are preferable to furred rodents, and should be offered only once each week or two. This species seems to have a quite high metabolism, and does best when fed small meals every 3-4 days.

Blue Tree or Blue-Spotted Tree Monitor, Varanus macraei
This strikingly colored lizard only appeared in zoos in the late 1990’s, and was not named as a distinct species until 2001. Never-the-less, beauty and small size (to 40 inches) has propelled it to the top of the “most desired species lists” of many monitor fanciers.

These slender monitors are jet black in color and variably patterned with blue spots and bands. The prehensile tail comprises 2/3 of the animal’s length.

Range
Blue tree monitors are found only on Batanta Island, Indonesia (off Irian Jaya, New Guinea). Almost entirely arboreal, they inhabit trees and shrubs within rainforests and estuarine swamps. Their wild status is unknown, but the species is listed on CITES Appendix II due to the extremely limited natural range.

Housing
Blue tree monitors require a spacious cage with provisions for climbing, UVB light and a basking spot of 90-95 F. The several pairs I’ve kept have co-existed without incident, and frequently rested in close contact with one another. Quite shy and quick to take flight, they do best in a well-planted cage provided with numerous hideaways and located in a quiet area. This is a species to observe, not handle.

Diet
The natural diet is likely composed largely of invertebrates such as tree crickets, katydids, snails, caterpillars and spiders, along with occasional treefrogs, lizards, small birds and their eggs, nestling mice and other small mammals.

As with other small monitors, I prefer not to feed too many rodents to this species. Mine thrive upon waxworms, crickets, crayfish, super mealworms, roaches, chicks and quail eggs. Pink mice are given every two weeks or so. Canned insects and monitor diets are often accepted and should be included as a source of dietary variety.

Breeding
Females lay 2-6 eggs at a time, and may produce up to 6 clutches per year (this may be a function of food availability in captivity). The young average 5 inches in length and hatch after an incubation period of 200-225 days. Captive females will bury eggs within moist substrates on the ground but seem to prefer arboreal nest boxes.

An Escapee that Made the Most of His “Vacation”
The long, slender tail of this monitor is prehensile and adds to its climbing abilities and agility. Alert and quick moving, blue tree monitors can catch even the swiftest of prey in their treetop homes. One individual that escaped from an exhibit at the Bronx Zoo was in the process of swallowing a house sparrow when I recovered him from atop a vine-covered fence!

In depth information about the family Varanidae and its individual species is posted at:
http://www.tigr.org/reptiles/families/Varanidae.html

Note: Please see The Monitor Lizards (Family Varanidae) – Family Overview and Species Accounts
for information on the natural history of monitor lizards.

Storr’s Pygmy Monitor, Varanus storri
This is the smallest monitor regularly available in the pet trade.   Also nearly the tiniest member of the family Varanidae, this species has much to recommend it as a “first monitor”.  Reaching just 14 inches in length, Storr’s monitor is one of the only monitors that can be housed within an aquarium-sized (see below) enclosure when adult.

A Popular Pet
Storr’s monitors are immensely popular because they combine all of the typical monitor traits in a small package – indeed, they act exactly like tiny versions of their larger cousins.  What they lack in size is more than made up for in attitude, and they are quite bold as captives.  In fact, keeping more than one in a cage, even a mated pair, is difficult due to their aggressive natures.

Range
This plucky, brown little lizard hails from northeastern Australia.  A subspecies, reddish in color but otherwise similar (V. s. ocreatus) ranges further west.  In the eastern part of its range, Storr’s monitor is threatened by the introduced marine toad, which both preys upon and competes with it.  Populations have all but disappeared from some areas already.

Housing
Storr’s monitors are quite active and should be housed in a tightly secured aquarium of at least 30 – 55 gallons (“long models are best”).  They require a source of UVB light  and a basking site that reaches 90 F or so.

Diet
Although they are often fed pink mice and small rodents in captivity, the natural diet of this species consists largely of insects.  The bulk of their food in captivity should be roaches, crickets, waxworms, super mealworms, mealworm beetles and wild-caught insects.  Canned insects, such as silkworms and grasshoppers, offer an excellent source of dietary variety.  Many individuals also accept canned monitor diets.

Breeding
Captive breeding is possible, but pairs must be watched closely for aggression.  The 2-5 eggs hatch in 100 days at 82F.

Crocodile Monitor, Varanus salvadorii

At the other end of the spectrum from Storr’s monitor is southern New Guinea’s massive crocodile monitor – it approaches 9 feet in length (nearly as long as, but much lighter than, the Komodo dragon), and there are unverified reports of much longer individuals.  The prehensile tail is twice as long as the snout-vent length.  Crocodile monitors are black in color and boldly marked with yellow spots, and sport long claws and a bulbous snout (particularly so in mature males).

Range
Highly arboreal despite their size, crocodile monitors dwell in the canopies of lowland forests in the vicinity of rivers and mangrove swamps.  Little is known of their status in the wild, but there is concern given the limited range; the species is listed on CITES Appendix II.

Warning!
In contrast to the other lizards described here, crocodile monitors are suitable only for very advanced hobbyists, or as zoo animals.  Those I worked with learned to tolerate my presence, but remained wary and agressive even after many years.

In contrast to the usual structure of monitor teeth, those of the crocodile monitor are serrated and over-lapping – possibly an adaptation to holding onto and carrying large prey high above the forest floor.  These animals are formidable predators, and capable of inflicting potentially life-threatening wounds.

Housing
Captive-bred animals are available and adjust moderately well (please see above) if given huge, high-topped enclosures that accommodate their arboreal lifestyles – forcing crocodile monitors to remain on the ground is, in my experience, quite stressful to them.

A cage or room of 10’ x 10’ by 10’ would be required for a single adult.  UVB light and a basking spot of 90-95 F are needed.  A humid environment is preferred, but they must be able to dry off as well.

Diet
Wild crocodile monitors feed upon cuscus, young tree kangaroos, naked-tailed rats, bandicoots, bats and other mammals, birds and their eggs, frogs, snakes, lizards and carrion.  Captives do well on rats, mice, chicks, crayfish, large roaches and hard-boiled eggs.

Image referenced from Wikipedia.

Check back on Friday for more Monitor Species Profiles.