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

Charles Darwin said of the lowly earthworm (Lumbricus terrestris): “It may be doubted that there are many other animals which have played so important a part in the history of the world as these lowly organized creatures”….this in deference to the fact that the 50,000 earthworms that may populate each quarter acre of farmland aerate and fertilize 18 tons of soil annually!

More to the point here, earthworms come close to being a complete nutritional package for many amphibians and certain reptiles.  Although based largely upon experience, this statement is also borne out by research…one study showed that earthworms provide adequate levels of several important nutrients, including Vitamins E and A, for many vertebrate species.

A Valuable Food for Many Pets

I have raised spotted and red salamanders and green, bronze and leopard frogs from metamorphosis through adulthood on an earthworm-only diet, and use them for 50-75% of the diets of many other amphibians.  Although refused by many lizards (but relished by American and European glass lizards), earthworms are taken by most predatory reptiles.

Larger earthworms, collectively termed “nightcrawlers”, offer a healthful alternative to rodents for those keeping largely insectivorous species (i.e. basilisks, African bullfrogs), which are often erroneously fed a rodent-based diet in captivity.

I’ve also had excellent results when using earthworms as the main food for bullheads and other fishes and for certain tarantulas and centipedes. They may also be fed to marine animals, but expire and decay rapidly in salt water.

Using Earthworms

Earthworms may be broken into small pieces to feed tiny pets.  However, a whole, small earthworm is more nutritionally complete than is a piece of a larger worm. Uneaten earthworms will remain alive in aerated freshwater for up to eight hours, but decompose rapidly upon death.

Obtaining, Storing and Breeding Earthworms

Earthworms may be purchased from bait stores and commercial breeders or collected, and store well in damp sphagnum moss under refrigeration.

Earthworms breed readily in captivity but, being intolerant of temperatures much above 70F (50-65 F is ideal), are best raised in a cool basement.  They can be easily cultured in a screen-covered garbage can filled with alternating layers of moist soil and dead leaves.  Ample air flow is important, but they will wander at night if left uncovered.

Earthworms can be raised on a variety of diets.  I use dead leaves, tropical fish food flakes, oatmeal and cornmeal, into which is mixed a powdered calcium supplement.  Placing the food on the surface, beneath a layer of damp burlap, simplifies collection.

Nutrient Loading

Earthworms consume large amounts of soil while feeding, and therefore their nutritional profile will vary with collection location.  If you buy eathworms for immediate use, try to feed the worms for a day or so as described above before offering them to your pets.

Earthworms and Pesticides

In the course of tunneling through the ground, earthworms may ingest pesticides and other harmful substances.  I’ve not had any problems with wild-caught worms, but a diet of earthworms contaminated with organochlorine pesticides has tentatively been linked to the disappearance of striped skunks on Long Island, NY.  If unsure, purchase your earthworms from commercial farms.

Further Reading

For more information on using earthworms and other invertebrates, please see my article Feeding Large Insectivorous Reptiles and Amphibians.

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.

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.

Snakes are well known for their abilities to survive long fasts – up to 2 years in some cases – without ill effect.  Working with ball pythons, diamondback rattlesnakes and various rat snakes, researchers at the University of Arkansas have recently shown that fasting snakes slow their metabolisms by up to 80%, and yet continue to grow even when food is withheld for 6 months.

Ball Pythons, the Champion Fasters

The reduced rate of metabolism may explain why many snakes lose little weight when fasting.  Keyed by circadian rhythms (“internal clocks”), ball pythons are notoriously worrisome to pet keepers in this regard.  Most refuse food for long periods of time each year, yet remain in good condition…in fact, the longest-lived captive snake is believed to be a ball python that attained approximately 51 years of age at the Philadelphia Zoo.

Growing Without Eating

The fact that fasting snakes continue to grow suggests that large size confers important survival advantages.  If it did not, precious fat reserves would not be allocated to growth during food emergencies.

Evidence from Zoo Animals – the Gharial

Other reptiles and amphibians seem possessed of similar abilities, although confirmation is lacking.  Fish-eating crocodilians known as Indian gharials (Gavialis gangeticus) are one example.  A group of 8 at the Bronx Zoo ceased feeding in tune with the cool season in their native Pakistan each year for the nearly 20 years that they were under my care.  They fasted for 3 months, but continued to move about and bask, and lost little of their 400-600 pound bulk during that time.

Other Reptile Pets

Bearded dragons and temperate zone reptiles, such as box and Eastern painted turtles, often stop feeding during the winter, even if kept warm.  Bearded dragons usually become largely inactive, but turtles often move about normally.  Despite this apparent use of energy, they lose little if any weight.

Interestingly, at least for turtles, individuals born in captivity usually remain active during the winter if kept warm, while wild-caught specimens typically go off feed for 2-6 months.

Know Your Pets’ Needs

Providing your pet with proper care and a healthful diet is vital if it is to survive seasonal fasts.  Be sure to research the species that you keep carefully.  Please consult our reptile and amphibian care books, and don’t hesitate to write in with any questions you may have.

Further Reading

To learn more about hibernation and fasting periods, please see my article Hibernation in Bearded Dragons and other Reptiles and Amphibians.