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

In Part I of this article we discussed the origin and current state of the problems associated with the long term use of goldfishes as a staple food for reptiles and amphibians.

Bait and Tropical Fishes

Fathead minnows, golden shiners and related fishes are preferable to goldfishes as a reptile and amphibian food, and may be used as dietary staples where appropriate. They are generally raised in outdoor ponds or wild-caught, and have fed on a variety of invertebrates, plants and other natural food items. This renders them a highly nutritious food item.

Whenever possible, you should alternate the species of fish offered. This is especially important for water and tentacled snakes, mata mata and alligator snapping turtles, Surinam toads and other species that feed primarily upon fish. Many common pet trade tropical fishes are nutritious and easily-reared, including swordtails, platys, guppies and mollies.

Food Market Fishes

Food market fresh water fishes (i.e. Tilapia and catfish), especially those which can be obtained whole, are another useful option. I fed the Bronx Zoo’s gharials (large, piscivorous crocodilians) on trout for many years…but that cost upwards of $1,000/month – 20 years ago!

Collecting Native Fishes

Where legal, you can add vital nutrients to your pets’ diets by collecting freshwater fishes via seine net, trap or pole. I always remove the dorsal and pectoral spines of catfishes, sunfishes and other well-armed species, just to be on the safe side.

Fish and Vitamin E

The Vitamin E question has also been investigated…I’ll write more on that in the future. For now, please be aware that frozen fish of any kind, used as a dietary staple for crocodilians and turtles, has been implicated in Vitamin E and other deficiencies. Marine fishes, frozen or fresh, seem to block vitamin absorption when fed in quantity to fresh water animals.

Further Reading

I must say that, food considerations aside, I like goldfish! Please check out our blog article Carnival Fish for some interesting background on their habits, care and long history as pets.

I frequently recommend wild-caught invertebrates as food for captive herps, birds, invertebrates and fishes. Today I’d like to address the thoughtful comments posted by some of our blog readers regarding potential pesticide contamination.

Secondary Poisoning

Secondary poisoning, the killing of animals other than the species that is the target of a pesticide, is an important concern whenever toxins are used.

Modern Pesticides

Commercial pesticides have evolved quite a bit since the secondary poisoning effects of DDT were documented in the 1960’s. Today, a combination of species-specific products and short half-lives (the time the pesticide remains lethal once applied) greatly reduces the risk to non-target species. This is especially true where West Nile Virus control and similar programs are undertaken by local municipalities…the chemicals used are carefully evaluated, and follow-up studies are implemented.

Secondary Poisoning Facts

As regards captive animals, the concern is that they will be affected by a pesticide after consuming food animals that have themselves been exposed.

While valid, such is not quite as likely as it may appear at first glance. Even as regards the highly publicized DDT scenario, the effects of DDT were manifested largely among top consumers (eagles, ospreys and other raptors) that consumed, over many years, fishes and birds that had concentrated the toxin in the course of feeding upon insects.

The non-target species were not killed outright, but the cumulative effects of the concentrated DDT rendered bird eggshells brittle and subject to breakage. There are, of course, exceptions…but, in any event, pesticides now in use are formulated so as to exert far less radical effects on non-target species.

Zoo Practices

During my 30+ years working with major zoos, aquariums and nature centers in the USA and Japan, wild-caught invertebrates have often been used to supplement the diets of reptiles, amphibians, birds and other creatures. The use of light-based insect traps (i.e., the Zoo Med Bug Napper) has been a standard practice in zoos long before my time in the field; laboratory analysis of invertebrates so collected has supported the safety of the practice as regards most species.

All major zoos use insecticides to kill roaches and rodenticides for mice and rats. Except in very unique situations, it is simply impossible to control such pests by other means. Roaches and mice survive for varying periods after being sprayed or consuming poison. During that time, they enter enclosures housing animals that prey upon them (this is well documented by cameras installed to record nocturnal behavior). During my time in the zoo field, the only local case of secondary poisoning that occurred involved a wreath-billed hornbill that consumed poisoned mice nearly exclusively over a period of years.

My Collection

In my collection, the use of native invertebrates dates back over 40 years. In a great many cases, animals that I have kept on such diets have reproduced and even set or approached longevity records (musk turtle, still alive at age 40; marine toads, 20+ years; African clawed frog, 19 years; weather loach, 19 years). My experience is echoed by many of the prominent hobbyists and herpetologists with whom I have long worked.

That being said, there are specific species and situations that warrant caution. I’ll cover these in Part II of this article.

Further Reading

Please see my article Collecting Invertebrates: an Entomologist’s Technique and the articles referenced there for further information.

Prehistoric cave paintings show that the pitfall trap, a simple covered or uncovered hole designed to capture animals, came into being very early in our evolution as a species.  Indeed, they are still used by hunters and field researchers today.  Pitfall traps also provide pet keepers with a simple, effective means of collecting live food for reptiles, amphibians, tarantulas, scorpions, mantids and other terrarium animals.

Building and Baiting the Trap

To create a pitfall trap, simple bury a can or jar flush with the ground and cover it with a board that is slightly elevated by small stones.  This will keep rain out while allowing invertebrates to enter.

An amazing assortment of creatures will simply stumble into such a trap, but you can increase its effectiveness by adding bait. A bit of ripe fruit, molasses, honey and some tropical fish flakes will lure all sorts of insects, sow bugs and other invertebrates (snails and slugs are especially fond of beer).  Be sure to keep some dead leaves or paper towels in the trap as well, to provide places for your catch to hide and keep away from one another.

Boards or other cover spread about an area, which can be easily turned and checked, will also attract a variety of insects. Spraying the area with a hose during dry weather will attract increased numbers of invertebrates to these shelters.

Cautions

Always use caution when examining your catch, as potentially dangerous spiders, scorpions, hornets and other such creatures may be present.  Have a good field guide on hand if you are unfamiliar with local species, and use feeding tongs to remove animals from the trap.

Native Beetles in the Terrarium

If your interests extend to native invertebrates, your trap will likely provide you with some pleasant surprises.

One of my favorite and rather frequent catches is the caterpillar hunter (Calosoma scrutator), a widespread beetle that feeds upon caterpillars and other soft-bodied insects (a relative, the forest caterpillar hunter, was imported to the USA from Europe in 1905 to battle gypsy moths).  Next time I’ll write a bit more about the natural history and captive care of these colorful, interesting, but largely over-looked beetles.

Further Reading

I have long relied heavily upon wild-caught invertebrates as food for animals in both zoo and my own collections.  In the past I have written about collecting leaf litter and arboreal insects, as well as devices such as termite traps and the Zoo Med Bug Napper.  Please see the following articles for more information:

Collecting Leaf Litter Invertebrates

Collecting Live Food: an Entomologist’s Technique

Building a Termite Trap

Collecting Live Insects for Birds

Image referenced from Wikipedia and orignally posted by

The value of UVB light to heliothermic (basking) reptiles has long been known.  Less well understood is the role of UVA light and how, in our attempts to provide reptile pets with light and heat, we often wind up affecting another of their critical needs: adequate air flow.

Today I’d like to provide some suggestions as to how we might effectively manage these three elements to provide our reptiles with healthy environments.

Ultraviolet B Light (UVB)

By basking under UVB light rays with a wavelength of 290-315 nanometers, many lizards, turtles and crocodilians synthesize Vitamin D3 in their skin.  Vitamin D3 allows these animals to utilize dietary calcium.  Without D3, dietary calcium is not metabolized and metabolic bone disease soon sets in.  Snakes, aquatic turtles and certain others can make use of dietary Vitamin D, but most species that bask must synthesize it in their skin.

While mercury vapor bulbs , the Zoo med 10.0 bulb and some others provide useful levels of UVB, nothing can replace natural sunlight. Measurements taken outdoors in the tropics (northern Australia) yield UVB readings of 450 microwatts/sq. centimeter…most florescent bulbs emit 13-35 mw/sq. cm.

Recent research indicates that chameleons and perhaps other reptiles can sense UVB levels (please see article below) and so may bask longer in captivity, but it is essential that we use a UVB meter to measure our bulbs’ output.

Ultraviolet A Light (UVA)

Recent research has shown that UVA radiation (wavelength 320-400 nanometers) promotes natural behavior, reproduction and the establishment of circadian rhythms (internal “clocks”).  UVA also affects how and what reptiles see.   Female desert iguanas, for example, cannot see the chemical trails laid down by males in the absence of UVA, and hence rarely reproduce unless exposed to it.

UVA bulbs are available, but we know little of the actual needs of most reptiles.

Air Circulation

Indoor glass terrariums with screen tops serve well in rendering heat and UV radiation readily available.  However, air circulation in such situations is restricted, creating an unhealthy situation for many animals.

Amphibians, chameleons and arboreal snakes from humid environments (i.e. green tree pythons and emerald tree boas) present special challenges.  The humidity they require can be supplied by foggers or via misting, but severe health issues arise if air flow is limited.  I still have a letter written to me in 1967 by famed herpetologist Wayne King, regarding blister disease in a northern watersnake.  Despite being highly aquatic, my pet needed air circulation and a dry basking site in order to remain healthy.

Screen Cages and Terrarium Top Enclosures

Screen cages  provide an ideal way to address each of the aforementioned concerns.  While glass and plastic filter out beneficial UV radiation, screen cages allow UVB and UVA to enter.  Being well-ventilated, they also offer excellent air circulation.

Screen cages can, if protected from predators, be utilized as permanent outdoor enclosures.  Even the largest models are very light in weight, and may be carried outdoors to provide periodic sunning opportunities.  In some cases, the cages can even be positioned in an open window…my friend does this for his water dragon, which is often seen perched in the sun 14 floors above West 23^rd Street in Manhattan!

Screen terrarium top enclosures  added onto glass terrariums present a unique solution to those with limited space.

Further Reading

Please see my article Chameleon Behavior is Affected by Vitamin D3 Needs  for insights into emerging research on reptile basking behaviors.

Image referenced from Wikipedia and originally posted by JialiangGao

Please see Parts I and II of this article for information on growing terrestrial and aquatic food plants for reptiles and amphibians.

Aquatic Invertebrates

A startling variety of aquatic invertebrates will likely establish themselves in almost any body of standing water, be it a backyard pond or a container of water on a fire escape in the heart of a busy city (the adults of most aquatic insects are winged, and quickly locate new breeding sites).  Ranging in size from tiny Daphnia to quite large dragonfly nymphs, all are fine food items for insectivorous herps, and make wonderful aquarium subjects as well.

You can also use an outdoor pond to breed snails, guppies, crayfish and other useful food animals.

Terrestrial Invertebrates

Your reptile garden will, in addition, attract numerous terrestrial insects.  All are interesting to observe and many can be collected to feed to your collection (a Bug Napper Insect Trap situated near a garden will provide a great nightly haul).

Flowering gardens are also important as feeding sites for pollinating insects, many of which are in serious decline.  Over 80% of the world’s plants and 90% of US food crops rely upon insect pollinators.

A Bonus…Observing Garden Visitors

You are sure to come across some interesting finds, as invertebrate diversity, even in temperate areas, is astounding.

An acre of Pennsylvania soil, for example, can host 425 million individual invertebrates (including 2 million tasty earthworms!) and New York State is home to 4,125 species of beetles.  Over 11,000 different types of moths may be found in the USA, and new species are constantly being uncovered in the most unlikely of places…be sure to check those captured in your Bug Napper carefully before popping them into a terrarium!

Further Reading

The leaf fall that gathers below your plants and trees will quickly become populated by an unbelievable assortment of millipedes, springtails, sow bugs, beetles and other creatures.  Many of these, especially the smaller invertebrates, are vital foods for tiny poison frogs and other small herps.  For information on collecting and using this free food source, please see my article on Leaf Litter Invertebrates.

Image referenced from Wikipedia and originally posted by Alvesgaspar