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

Released and escaped green iguanas (Iguana iguana) have now established huge populations in southern Florida. Although I must admit to a certain degree of fascination with introduced species, there can be no doubt that the massive lizards have caused a great many problems in their adopted environment.

An Impressive but Bothersome Invader
Normally arboreal, iguanas adapt to treeless environments by commandeering burrows occupied by the endangered burrowing owl (Athene cunicularia), displacing the birds and destroying eggs and chicks in the process. Ever hungry, the 4-6 foot long behemoths also assist the spread of undesirable invasive plants by eating their fruits and dispersing the seeds in their feces.

Among one of their most troublesome characteristics is a propensity to colonize airway strips and nearby areas. Green iguanas in Puerto Rico have caused runway accidents, and they are considered a collision hazard in Florida airports as well.

Raccoons in Cities and Nature Preserves
Raccoons, although native, have also become problematical in recent years. Now well adjusted to people, they thrive everywhere…during my years as a nuisance wildlife trapper, I caught scores throughout NYC, including in some of Manhattan’s most densely-populated neighborhoods.

Raccoon populations in south Florida parklands reach 250 animals per square kilometer – 200 times the densities of those dwelling in natural habitats! In addition to serving as a reservoir for rabies and distemper, raccoons in Florida pose a serious threat to the nesting success of green, loggerhead and other marine turtles.

Please check in next week to see how a well-planned control program for both iguanas and raccoons went astray…and would up helping the iguana population to grow astronomically!

Further Reading
Iguanas make fascinating pets, but, as males may exceed 6 feet in length, they are not for the unprepared. Please read our cage guide, Green Iguanas, before you take on one of these impressive giants. Green Iguana image referenced from Morguefile.

While reviewing the outdoor aviaries that were recently added to out line of bird cages, it struck me that these large, sturdy enclosures could be put to good use by reptile and amphibian keepers. Outdoor pens, both at home and in zoos, have given rise to some of my most enjoyable times and memorable observations.

In addition to allowing space and opportunity for a wide range of behaviors, outdoor aviaries promote good health and reproduction by exposing pets to sunlight, natural day/night and weather cycles, and dietary variety in the form of wild invertebrates. My first crude outdoor pen, populated by green frogs and spotted turtles, provided, even to an unskilled 10-year-old, a first peek at herp reproduction and hibernation.

An outdoor aviary equipped with a can provide a lifetime of enjoyment….if you focus on native species, your workload will be minimal and breeding a very real possibility. Although unenclosed ponds also have great potential, many frogs wander and predation by dogs, raccoons, herons and other animals is an ever-present concern. Our outdoor aviaries will keep your pets safe and contained. They are available in 5 sizes, ranging from 3.5′ x 4′ to 9′ x 5′, and with bars spaced ½ inch and 1 inch apart.

Certain reptiles, such as adult green and rhinoceros iguanas, spur-thighed (“Sulcata”) and other large tortoises, tegus, and larger monitors are almost impossible to keep properly indoors. Others fare far better when given outdoor access for at least part of the year…success with chameleons, for example, nearly always soars once they are introduced to well-planted outdoor cages. They and other species are often stimulated to breed by a change in environment as well. Mixed species displays and many arboreal animals are also far easier to accommodate in large outdoor quarters.

A spacious aviary can also allow for the keeping of multiple-male colonies of territorial lizards, which will give you a unique view of display and reproductive behavior. I have worked with groups of sungazers, red-headed Agamas and various dabb lizards set up in this fashion…I learned a great deal in the process and enjoyed myself immensely.

Further Reading
For more information on keeping herps outdoors, please see my articles on Red-Eared Sliders in Outdoor Ponds and Bullfrogs in Outdoor Ponds.

With spring finally here, my thoughts are turning to growing food plants and collecting insects with which to feed my collection.  Happily, these two activities are intertwined – plants attract insects, and insects pollinate plants.  Garden-grown plants provide minerals and trace elements that are often difficult to supply otherwise, and their fiber content is usually quite high.

Your pets’ enthusiastic attacks on novel foods will leave no doubt as to their value in stimulating appetite and behavior.  Tortoises and iguanas will spend hours happily picking through piles of fresh greens…more so if they can forage in outdoor pens atop growing plants.

Tortoises

Tortoises of all types, especially those maintained on a limited number of food items during the winter, invariably improve in condition when offered wild plants.  During the warmer months, natural forage can account for up to 85% of the diets of most species.  A pair of spur thighed tortoises, each of which weighed in at 80-90 pounds, fared very well on such a regime during the years that they were under my care at the Prospect Park Zoo.

If your tortoise or iguana is maintained on natural foods for a portion of the year, the balance of the diet can be comprised of a high quality commercial tortoise or iguana chow.

Herbivorous Lizards

Green, rhinoceros and desert iguanas, Uromastyx spp., chuckwallas and other herbivorous lizards become very excited as soon as novel fresh foods are offered.  It is difficult to get across just how much they change in demeanor but, once seen, their reactions will quickly convince you of the value of your efforts.

Aquatic Turtles

Don’t forget your aquatic and semi-aquatic turtles – cooters, American and Asian box turtles, wood turtles, Amazon side-necks and a host of others relish greens, fruits and vegetables.  Actually, painted turtles and red-eared sliders should be gradually switched to a plant-based diet as they mature.  This may take some time and creativity, but is well-worth your efforts.

The Ever-Abundant Dandelion

April and early May is dandelion-blooming time in the northern half of the USA, and nearly every herbivorous reptile relishes its leaves and, especially, the bright yellow flowers.  You can harvest this nutritious plant nearly anywhere…just be careful around homes as it is considered pest (a phenomenon that has baffled me since childhood!) and is often attacked with herbicides.

I have long used dandelion flowers to spur activity in zoo exhibits…by placing them in out-of-the-way locations, I was able to induce a great deal of interesting foraging behavior.  This was of such obvious value to the animals that I continue to freeze dandelions for winter use in my own and public collections.

Hardy Self-Starters

A number of plants that readily colonize bare patches of earth, and which need little care, are also highly valuable additions to reptile diets.  Especially hardy are clover (Trifolium), honeysuckle (Lonicera), thistle (Sonchus), bramble (Rubus) and various wild grasses.

Other types of browse that produce tasty stems, leaves and roots include various mallows (Malva), cat’s ears (Hypochoeris), Clamatis and Sedum.

Further Reading

Please see my article on Toxic Plants  for some cautions.  It was written with birds in mind, but is a good general reference.

Wild-caught insects and other invertebrates are valuable, and often essential, additions to the diets of many captive reptiles and amphibians.  During the warmer months, I have utilized them for 50-100% of the diets of many animals in my own collection, and for those under my care in zoos.

Beating the Bushes for Insects

One of the simplest and most effective collecting techniques was developed by entomologists (insect scientists) who needed to sample large habitats quickly.  Here it is: a white, un-patterned sheet is spread below a bush or tree, and the foliage is then beaten with a stick.  That’s it!

An incredible assortment of caterpillars, beetles, ants, tree crickets, katydids, spiders and other tasty morsels will rain down upon the sheet, where they can be easily collected.  The majority will be arboreal species – healthful additions to the diets of tree frogs, flying geckos, smooth green snakes and other tree-dwelling creatures, and to all other insectivorous herps.

Identifying Potentially Troublesome Species

Do not collect fireflies, “hairy” caterpillars (please see photo), and brightly colored insects that you cannot identify (due to possible toxicity).  Unless you are well-acquainted with local spiders, it is best to avoid them as well…harvestmen, or “daddy long-legs”, however, are harmless.

Use our plastic tongs to handle any specimens that may bite or sting.  A Peterson or Audubon Society field guide will help you to learn about the innumerable interesting creatures that you will encounter.

A World of Possibilities

You’ll have quite a selection to choose from, wherever you live.  Over 2,000 types of insects live right within New York City, and it is estimated that 30 million species inhabit the planet.  A single tree in Panama has yielded 130 species of beetle, 100 of which were new to science!

Last summer I was pleasantly surprised to find the spectacular eyed click beetle (Alaus oculatus) pictured below in my haul (this fellow was released).

Insect Traps and Canned Insects

The Zoo Med Bug Napper is another very useful insect-collecting tool.  An alternative means of introducing variety to your pets’ diets is through the use of canned invertebrates.

Further Reading

An amusing story involving the “bush beating” technique is given in fabulous book To the Zoo in a Plastic Box (Newmark, 1965; Random House).  A hilarious and informative account of two brothers’ adventures collecting insects and herps for the London Zoo, the book is a true gem…please read it if possible.

Please see my other insect-collecting articles as well – Leaf Litter Invertebrates and Building a Termite Trap.

Formulating a balanced diet for medium to large sized insectivorous reptiles and amphibians poses a unique set of problems.  Large insects are difficult to come by in sufficient quantities, and rodents, as we shall see, are often a poor substitute.  Canned insects, especially large grasshoppers, offer a convenient and healthful alternative.

Surprising Research on Natural Diets

Many carnivorous reptiles and amphibians prey almost entirely upon invertebrates in the wild, despite being rather large in size.  The most extreme example may be found among certain populations of savannah monitors, which eat locusts and snails to the near exclusion of all else.

Even the rapacious marine toad, capable of downing a half-grow rat, falls into this category.  In a Herpetologica article published some years ago, stomach analysis of several thousand toads collected in the central llanos country of Venezuela revealed not a single vertebrate prey item…this despite the fact that small rodents, lizards and turtles abound there.

The Problem for Pet Owners

The appetites of a number of commonly kept reptiles and amphibians are difficult (and expensive!) to satisfy with crickets, mealworms and waxworms, leading pet keepers to turn to mice.  However, while most largely insectivorous species will take a rodent on occasion in the wild, their digestive systems are not designed to process such food on a regular basis.

Health Problems Related to Improper Diets

Insectivorous herps that are fed a steady diet of rodents often develop health problems, which frequently show up as lipid deposits in the eye, resembling cataracts.  Fatal liver and kidney disorders may follow.  While cholesterol seems to be the major culprit, intestinal blockages from fur and bone have also been documented.

I have noted these problems, many confirmed by autopsy at the Bronx Zoo, in basilisks, tiger salamanders, Cuban treefrogs and White’s treefrogs.  Other species that may fare poorly on rodent-based diets include smaller monitors (i.e. black tree and Merten’s water monitors), American and African bullfrogs, frilled dragons, marine and Colorado River toads and horned frogs.

Canned Grasshoppers

Canned grasshoppers, offered via tongs, provide an ideal solution to this dilemma.  The grasshoppers selected for canning are large enough to satisfy hearty appetites, nutritionally sound, easy to coat with powdered supplements and captive raised to avoid pesticide-related concerns.  Zoo Med  supplies large, wingless grasshoppers, while Exo Terra’s  grasshoppers are winged.  Wingless grasshoppers are best for medium-sized pets, such as White’s treefrogs.

Canned grasshoppers are also relished by many turtles (i.e. box, wood, snapping, Australian snake-necked), sugar gliders, flying squirrels, hedgehogs, hill mynas, emperor scorpions, tarantulas and other pets with carnivorous leanings.  Oscars, peacock bass and other large aquarium fishes love them…and they make great fishing bait!

Other Large Invertebrates

Culturing roaches and collecting cicadas are also useful options for owners of large insectivorous pets.  Please see my articles The Orange Spotted Roach and Cicadas  for details.  For information on other types of canned invertebrates, please see Canned Insects and Other Invertebrates.

Crayfishes are an ideal, high calcium food for many large herps.  Where legal, they can be caught by trap, seine or hand line (this last is actually great fun, and has resulted in a few “trophy-sized” catches for me!).

Further Reading

The summary of an interesting experiment dealing with the effects of a high cholesterol diet on Cuban treefrogs is posted at http://www.bioone.org/doi/abs/10.1638/1042-7260%282001%29032%5B0305%3ACLDICT%5D2.0.CO%3B2?journalCode=zamd.