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

A Control Program Backfires
Please see Part I of this article for background information. With introduced green iguanas (Iguana iguana) driving endangered burrowing owls from their nests and raccoons (Procyon lotor) devouring sea turtle eggs, the Florida Department of Environmental Protection initiated control measures. At a preserve in Dania Beach, an intensive trapping and collection campaign greatly reduced the numbers of both species, but an unexpected consequence of these efforts soon became apparent.Within a year of the raccoon numbers being brought under control, iguana populations skyrocketed. In one area of the park, researchers counted 626 iguanas per square kilometer (0.4 square miles)…an unprecedented density for any lizard species!

It seemed that raccoon predation had been a very effective control on iguana numbers. Although hawks, gray foxes, night herons, alligators and other animals prey upon iguanas, only raccoons take eggs, hatchlings and sub-adults in significant numbers.

Iguanas…Here to Stay?
Young iguanas are now especially common at the site, pointing towards an even greater population increase in the future. Hand-collection, although possible, is a daunting task, so biologists are looking into alternate control measures. Meanwhile, spurred by ample food and little competition, lizards as young as 2 years of age are laying eggs.

In Belize, black rats effectively control one green iguana population by taking nearly every egg laid. However, Florida’s parks already have enough problems without black rats…in fact, their notorious cousin, the Norway rat, is already a resident of many!

Further Reading
It was my good fortune to work with green iguanas in a natural, if somewhat unusual (i.e. treeless) habitat. Please see my article, The Green Iguana on the Venezuelan Llanos  for the story.

To learn more about the challenges and rewards of keeping these impressive lizards, please check out our care guide, Green Iguanas.

Watersnakes are largely ignored by herptoculturists, and I’ve never quite understood why. Hardy, prolific, and often colorful, their utilization of two habitats makes for very interesting observations. Today I’d like to focus on the northern watersnake (Nerodia sipedon sipedon), and to mention a few others.

Description
Background color varies through shades of pale gray to dark brown, with reddish to black cross-bands. Juveniles are brightly marked, while the colors of older animals usually darken. Stoutly built, the northern watersnake may reach 4 ½ feet in length, but averages 3 feet.This species interbreeds with its subspecies, the midland water snake, which may confuse identification at range overlaps.

Range
The range extends from southeastern Quebec, Canada to North Carolina, Alabama and Mississippi. Related subspecies occur as far west as Colorado.

The endangered Lake Erie water snake (N. s. insularis), a subspecies of the northern, is found only along Put-In-Bay, Lake Erie.

Habitat
The northern water snake frequents swamps, ponds, lakes, rivers and streams. It rarely strays far from the water’s edge, but frequently basks on logs and overhanging branches. Although preferring quiet waters, I sometimes encounter them along swiftly flowing rivers.

Status in the Wild
This snake can build up large populations in suitable habitat but, in my experience, does not adjust well to human presence (it is sometimes killed in the mistaken belief that it is venomous and reduces game fish numbers).

Several years ago I visited formerly well-populated ponds on Long Island, NY, as part of a government-sponsored survey. Despite adequate habitat and a healthy prey base, I found nearly all to be barren of snakes, and local fishermen confirmed their absence.

Diet
Watersnakes seem almost “crazed” when food is scented. Legendary reptile man Raymond Ditmars reported catching them on fishes tied to a string, a feat I repeated a half-century later with admirable results. I have also taken them in minnow traps.

Watersnakes feed upon a wide variety of frogs, tadpoles, salamanders and fishes and crayfishes.

Reproduction
Mating occurs in early spring. The young, 9-100 in number, are born alive after a gestation period of 2-3 months (March-July).

Miscellaneous
This snake was once common within NYC but has declined dramatically. I re-introduced it to the grounds of the Bronx Zoo in 1986, and a small breeding population is now to be found there.

Northern water snakes are harmless but aggressive when disturbed, and are often mistaken for the venomous water moccasin. The confusion is greatest in the Southeastern USA, a watersnake-lovers paradise, home to 12-15 subspecies. The massive Florida green water snake (N. floridana) reaches 6 feet in length and even holds its mouth open when threatened, in a manner reminiscent of the moccasin’s display.

Various watersnake species regularly hybridize, producing a bewildering array of forms in the species-rich southeast. Despite the passage of over 20 years, I still clearly recall a gorgeously-patterned individual that I narrowly missed capturing in south Florida. It was almost certainly a mangrove watersnake (N. clarkii compressicauda), perhaps hybridized with a Gulf salt marsh or Florida watersnake. I realize that my awe seems odd in these times of captive-bred “designer snakes”, but to encounter such a creature in the wild was quite a thrill.

Further Reading
You can learn more about the natural history of the 10 Nerodia species at http://www.jcvi.org/reptiles/search.php?submit=Search&exact%5B%5D=genus&genus=Nerodia.

Nerodia sipedon image referenced from Wikipedia and originally posted by Brian Gratwicke

Nerodia rhombifer image referenced from Wikipedia and originally posted by LA Dawson.

A surprising number of largely carnivorous lizards, especially various geckos and anoles, consume sap, flower nectar and overripe fruit in the wild. Providing a substitute in captivity is a good way to increase dietary variety. Also, as many find sweet liquids irresistible, by mixing in vitamins and minerals you can help ensure a nutritious diet.

Sugar Water to Nectar Mix
Well, we’ve come a long way since the anole “sugar water days” (the recommended diet for green anoles sold at circuses in the 1960’s). Following is a mix that I and others have found useful for anoles, geckos, basilisks, skinks and others.

1 jar of fruit-based baby food (papaya, banana, apricot or mixed)
1 tablespoon of honey (alternate with molasses)
1 dropper of Avitron Bird Vitamins (although formulated for birds, Avitron is a tried and true ingredient)
1 teaspoon Repti Calcium (without D3)
Water should be added to achieve a consistency favored by the species that you keep – i.e. nearly solid for New Caledonian giant geckos, watery for Jamaican anoles.

Additional Notes
Some folks add bee pollen, which seems not to affect palatability, and may add useful nutrients.

Experiment with different flavors, as some species are quite particular. Try also adding some mashed, overripe bananas, oranges, mangos and other fruits to the mix (for giant geckos, this is a must).

Nectar for Beetles, Roaches and Moths
If you are like me and favor invertebrates as well, you’ll find this mix very useful in keeping Hercules, goliath, rhinoceros, stag and other tropical and native beetles.

Most roaches devour it eagerly. I have used this and similar mixes to quickly nutrient-load roaches destined to be fed to delicate captives, and for Cuban green and other species in zoo exhibits.

As a side note, if you enjoy observing moths, or collect them as food for your animals, try smearing a tree trunk with honey or molasses. This old insect-collector’s trick has yielded me huge, spectacular Cecropia and polyphemus moths right in the heart of New York City!

Prepared Nectar Mixes
Nectargold for Lories and Lorikeets is a highly nutritious multi-fruit nectar mix. It is supplied dry, and so can be stored until needed. Many creatures will accept it as is, or you can tweak the recipe with honey or other favorites.

Further Reading
Some anoles take nectar so regularly that they may actually function as important plant pollinators. For more information, please see the following note in Herpetological Review

Rhacodactylus leachianus image referenced from Wikipedia and originally posted by Alfeus Liman.

Concerns over the use of goldfishes (Carassius auratus) as a food item for reptiles and amphibians have long been recognized, yet there remains a bit of confusion on the topic. References to Vitamin E deficiencies in animals kept on fish-based diets, a separate problem entirely, often further clouds the issue. Prompted by recent comments on our blog, I thought I might address the subject in this article.

Goldfishes and Large Pets
The controversy is important because goldfishes are the least expensive and most readily available “feeder fish”. They are also available in a wide variety of sizes, allowing owners of large reptiles and amphibians to offer their pets a whole fish, and a more substantial meal than a large golden shiner. This is preferable, from a nutritional standpoint, to feeding cut pieces of a Tilapia or other large food-market fish.

A Valuable Resource for Live-Food Specialists
Goldfishes are also quite hardy and usually remain alive when introduced into an aquarium, even when subjected to large temperature changes (drastic temperature changes quickly kill other typical feeder fishes, such as golden shiners and fathead minnows). This allows us to more easily feed aquatic live-food specialists, such as mata mata turtles and tentacled snakes, and American bullfrogs and other large amphibians.

I once cared for a large, wild-caught alligator snapping turtle that refused to eat fishes unless, as in nature, they investigated his tongue’s “fishing lure”. Goldfishes adjusted so well to the exhibit’s water that they would try to eat the turtle’s worm-like lure in short order.

The Origin of the Goldfish Problem
I was fortunate in having been involved in the specific incident that led to the discovery of the nutritional problems associated with goldfish-based diets. During my early years at the Bronx Zoo, it was noticed that mata mata turtles (Chelus fimbriatus) that were fed solely upon goldfish thrived for about 5 years, and then died suddenly. The odd phenomenon, it turned out, was not limited to the Bronx Zoo, and had occurred in several other collections.

Necropsies of the turtles revealed liver and kidney damage, and problems indicative of Vitamin A overdose (this last was later disputed, and has not been proven conclusively).

Using Goldfishes
Experience has since established that goldfishes may be safely fed to reptiles and amphibians on an occasional basis, i.e. once monthly, but should not be used as a dietary staple.

Another Concern?
Some years ago, I came to learn that some commercial goldfish farms raised their stock largely on chicken droppings supplied by local poultry farms (goldfishes, it seems, are quite hardy…and goldfish farm owners equally resourceful!). I do not know if this is still the case, but often wondered about the possibility of Salmonella contamination. I’ve never run across or read of a problem…but looking into it might make for an interesting project.

Further Reading
Please check out the following article for another experienced turtle keeper’s view on goldfishes as a food item, and for a description of the mata mata turtle’s unique strategy of “herding” fishes and other prey.
http://www.tortoise.org/archives/matamata.html.

Bent-toed geckos (Genus Cyrtodactylus, i.e. C. louisiadensis and C. irianjayaensis) are becoming ever more popular in captivity but, while a fascinating group, their care is often fraught with difficulties, and there is a great deal of conflicting information being circulated. A recent note from blog reader Dave, upon whom I can always count for interesting comments and questions, brought these wonderful creatures to mind again.

Dave noted the scarcity of husbandry information regarding bent-toed geckos, and mentioned that his lizard, purchased as a giant bent-toed gecko, was not feeding with very much vigor. Following are some exerts from my response to Dave, along with a few additional notes.

The Genus Cyrtodactylus
So far, 115 species have been described in the genus Cyrtodactylus. The giant bent-toed gecko is often sold as the “New Guinea phase” of C. louisiadensis, but is actually a separate species, C. irianjayaensis. To further confuse matters, stores sometimes mix up the various species, and coin their own names.

There are still many questions as regards the husbandry and natural history of the giant bent-toed gecko. Over the years, I’ve had a number of little known species of the same genus (Cyrtodactylus) pass through my hands, and have found the following general principles to be of use.

The Importance of a Secure Environment
Give the animal as much space as possible, with lots of cover and places to climb…suspended pieces of rolled cork bark make perfect shelters. Bent-toed geckos are very stress-prone, but don’t always exhibit the behavioral signs of stress – flight, panting, threat displays – so commonly seen in other lizards; disturb it as little as possible. These are definitely animals to observe, not handle. A night-viewing bulb will allow you to watch the lizard as it goes about its nocturnal wanderings without undue disturbance.

Providing Security
One useful technique that works with animals of all types is to provide a solid wall or two. You may notice that well-run zoos rarely exhibit animals in cages having all sides are open to view.

In an aquarium, you can cover some of the glass with dark paper or cardboard. Even where shelters are available, this simple step often makes a great difference in the animal’s welfare, and brings about immediate changes in its behavior.

Next time I’ll cover lighting and feeding, including a note on the use of snails in the diet of this and related geckos.

Further Reading
A listing of all species with the genus Cyrtodactylus, along with range information, may be found at
http://www.jcvi.org/reptiles/search.php?submit=Search&exact%5B%5D=genus&genus=Cyrtodactylus

The image pictured above  was referenced from Wikipidia and features a related species; not the Giant Bent Toed Gecko. Originally posted by W.A. Djatmiko.