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

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.

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.

 

 

Shocking as it may be to anyone with even a passing awareness of conservation issues, tiger salamander larvae (Ambystoma tigrinum) are still widely used as fishing bait throughout much of the USA.  Run through with hooks while alive, the 6-10 inch amphibians are wildly popular with anglers seeking bass, pickerel and other fishes.

Disease and the Bait Trade

Recently (April, 2009), biologists at the National Science Foundation announced that a significant percentage of larvae in the bait trade have tested positive for the deadly Chytrid fungus Batrachochytrium dendrobatidis.  This fungus has decimated amphibian populations on nearly every continent, and is responsible for the extinctions of local populations and, most likely, entire species.

Herpetologists are working feverishly to control its spread, but are as yet unable to understand why the fungus has become such a devastating problem in recent years.  Often, the only hope for amphibians in its path is captivity   – colleagues of mine recently collected an entire population of Panamanian golden frogs, but the long-term outlook is quite dim.

Virulent ranaviruses, which quickly kill many amphibians, have also been identified in larvae sold in bait shops in Arizona, Colorado and New Mexico.

Hybridization

As if the all this were not enough, the release of bait trade salamanders has resulted in the hybridization of critically endangered California tiger salamander populations (released barred tiger salamanders mated with the California subspecies).

Hybridization threatens survival by altering critical components of the genome.  For example, when various subspecies of ibex (mountain goats) were released together in Spain, the resulting hybrids gave birth during the winter, and the population became extinct.

Getting Involved

Partners for Reptile and Amphibian Conservation http://www.parcplace.org/, an organization of professional herpetologists and interested citizens, supports numerous research programs.  Please be in contact to learn more about this issue and their many interesting volunteer opportunities.

Next time I’ll discuss other threats to tiger salamanders, their conservation status, and problems regarding food market bullfrogs.  

Further Reading

Please see my book Newts and Salamanders  for information on the natural history and captive care of tiger salamanders and their relatives.

Image referenced from morguefile.

 

 

Many aquatic turtles make wonderful pets, but nearly all share one troublesome trait – they are messy feeders, and keeping their water clear is often a major challenge.  Today I’d like to present a simple, time-saving feeding technique and review some helpful products such as undergravel filters and gravel washers.

Separate Feeding Containers

In both zoo collections and with my own aquatic pets, I have found removing the turtles from their aquarium for feeding to be the most effective way of maintaining water quality.  Nearly all turtles adjust readily to this, and feed without difficulty in plastic tubs or other easily-cleaned containers.  I’ve had difficulties only with a few retiring species, such as mata mata turtles (Chelus fimbriatus) and giant soft-shelled turtles (Pelochelys bibroni).  For these, extra space and cover in the form of floating plants did the trick.

Leave the turtles in their feeding container for 20 minutes or so after they finish eating, unless such is stressful for them (turtles are very perceptive…some are uncomfortable in strange surroundings and will try to escape after feeding).  Elimination is swift, and many pass stored wastes shortly after eating.

Partial Water Changes

In terms of water clarity and ammonia management, partial water changes are as important for turtles as for aquarium fishes.  Soft-shelled and Fly River turtles (Carettochelys insculpta) are particularly sensitive to poor water quality, but it is a concern for all species.

When doing a water change, use a gravel washer to pull water from the very bottom of the aquarium.  This is a good idea even if you keep your turtles in a bare bottomed tank, and essential if you use gravel as a substrate.

I’ve found it very useful to siphon water from the aquarium into the feeding container at meal times – this assures frequent water changes and has allowed me to keep even quite large snapping turtle (Chelydra serpentina) and giant musk turtle (Staurotypus triporcatus) aquariums crystal clear.

A Caution

One important point: do not start a siphon by drawing on its end with your mouth to fill the tube, as aquarium water should never be ingested.  Lee’s Self-starting Gravel Cleaner  is the best model to use with turtles.  If you choose a sink-compatible gravel cleaner, be sure to drain the waste water out a door or into a basement sink, and not to one used for food preparation.

Undergravel Filters

An undergravel filter will turn your entire filter bed into a living filtration unit.  Gravel washing and partial water changes are still necessary, but if powered by a suitably strong aquarium pump, an undergravel filter will go a long way in easing tank maintenance.  I use them either alone or in conjunction with canister or other mechanical filters, depending upon the circumstances.

Food Selection

For those times when you must feed your turtles within their aquarium, choosing a suitably-sized food item will assure that less of it winds up floating about and clouding the water.  Please check out our pelleted turtle foods  for some ideas as to the sizes that are available.

Further Reading

Large species such as snapping turtles and alligator snapping turtles are interesting, but pose serious husbandry difficulties for most hobbyists.  For some ideas and tips, please see my article The Captive Care of Snapping Turtles and Alligator Snapping Turtles.

 

Please see Part I of this article for information regarding specific types of reptiles and the growing of native plants.

Nearly all fruits and berries, and many flowers and grasses, can be put to good use in feeding tortoises, herbivorous lizards, and certain aquatic turtles.  Try also adding grass clumps and leafy branches to your insectivorous pets’ terrariums…frogs, day geckos and others will enjoy poking through them in search of tasty insects.

Fruit Trees and Bushes

Apple and Crab Apple

Figs

Apricots

Pears

Peaches

Most berries, including natives such as elderberry and juniper

Flowers

Dogwood

Magnolia

Dandelion

Gardenia

Nasturtium

Petunia

Petunia

Begonia

Bougainvillea

Seeds, Grains and Grasses

Thistle

Canary Grass

Maize/Corn

Sunflower

Seeds of most native grasses (“weeds”)

Pond Plants

A small pond, or even an unfiltered, water-filled container set out in a sunny location, will support duckweed, Anachris and other hearty aquatic plants, many of which are important natural foods for aquatic turtles.  Keep a few minnows in the pond to consume mosquito larvae.

You can also easily (almost too easily!) grow water hyacinth and water lettuce – both look great in terrariums housing frogs, newts and small turtles.  They require very bright light, but you can always rotate individual plants back out to the pond, where they will perk up very quickly.

Next time I’ll highlight some interesting insect visitors that you can expect in your reptile garden.

Further Reading

Fruit and other trees attract cicadas…a mixed blessing for “real gardeners” but a bonanza for herp enthusiasts.  For my take on using these chunky summer songsters as reptile food, please see Cicadas, an End of Summer Treat.