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

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.

So it was with great interest that I began experimenting with the whole, canned invertebrates that have recently become available. Animals that normally consume non-living foods, such as box, musk, snapping, painted and spotted turtles, sharp-ribbed and fire-bellied newts and African clawed frogs, eagerly took most foods offered. I was also able to tong-feed the insects to several species of “live food only” amphibians, including horned frogs, green frogs, leopard frogs (see photo), American bullfrogs (see photo, albino frogs pictured here), gray treefrogs, barking treefrogs, spotted salamanders and fire salamanders (see picture.)

I’m very eager to try these products on several small, insectivorous snake species which do not thrive unless supplied with caterpillars, slugs, and grasshoppers. First among these would be North America’s gorgeous smooth and rough green snakes, Opheodrys vernalis and O. aestivus, followed by the ring-necked and red-bellied snakes, Diadophis punctatus and Storeria occipitomaculata (these last 2 favor slugs, for which snails might be a good substitute).

I was especially happy to see that snails were being offered by several companies. Since childhood, I have longed to successfully keep the striking Malayan snail-eating turtle, Malayemys subtrijuga. I have had moderate success in zoos, but only when large breeding colonies of apple snails were available to feed these beautiful food specialists. Supplying enough food is difficult for hobbyists and most zoological parks, and hence this turtle is rarely bred or even kept in captivity, despite being extremely rare in the wild and in need of our help. I look forward to trying again, using canned snails, supplemented with live ones, as a basis of the diet.

I have also written about the use of canned insects in bird diets – please see my article, Feeding Insects to Pet Birds.

I have tried most of the following, and recommend you to experiment as much as possible:

Exo Terra – grasshoppers, silkworms, snails
Zoo Med – grasshoppers, caterpillars, snails
Jurrasidiet – Snails, grasshoppers