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Feeding Large Insectivorous Reptiles and Amphibians: Problems and Solutions

Basilisk PairFormulating 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.


About Frank Indiviglio

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Being born with a deep interest in animals might seem unfortunate for a native Bronxite , but my family encouraged my interest and the menagerie that sprung from it. Jobs with pet stores and importers had me caring for a fantastic assortment of reptiles and amphibians. After a detour as a lawyer, I was hired as a Bronx Zoo animal keeper and was soon caring for gharials, goliath frogs, king cobras and everything in-between. Research has taken me in pursuit of anacondas, Orinoco crocodiles and other animals in locales ranging from Venezuela’s llanos to Tortuguero’s beaches. Now, after 20+ years with the Bronx Zoo, I am a consultant for several zoos and museums. I have spent time in Japan, and often exchange ideas with zoologists there. I have written books on salamanders, geckos and other “herps”, discussed reptile-keeping on television and presented papers at conferences. A Master’s Degree in biology has led to teaching opportunities. My work puts me in contact with thousands of hobbyists keeping an array of pets. Without fail, I have learned much from them and hope, dear readers, that you will be generous in sharing your thoughts on this blog and web site. For a complete biography of my experience click here.
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