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.

Small, shrimp-like marine crustaceans known as krill have long featured prominently in the diets of aquarium fishes.  I’d like to relate here some personal experiences that point to their value as food for turtles, tadpoles, newts and salamanders.

Krill as Turtle Food

Some years ago a herpetologist of my acquaintance, noting that krill were quite high protein and calcium, decided to use this food as a major part of the diet of a group of Blanding’s turtles (Emydoidea blandingii) that had hatched in his collection.  The diet he used, simple by current standards, was comprised of 50% freeze-dried krill and 50% Reptomin Food Sticks.  The turtles matured into beautiful, healthy adults with hard, well-formed shells…not always an easy task in captivity.  I later successfully repeated the experiment with a clutch of Eastern painted turtles (Chrysemys picta).

Amphibians

The diet fed to tadpoles greatly influences their survival rate during the stressful period when they transform into frogs.  I have found that species typically considered to be herbivorous, such as bullfrog and spring peeper tadpoles, actually fare much better when protein such as krill is included in their diets.  Newts, amphiumas, axolotls and African clawed frogs relish krill as well.

Useful Products

We carry a wide variety of freeze dried and frozen krill of various sizes at ThatFishPlace/ThatPetPlace.  You will also find krill and shrimp in Reptomin Select-A-Food, Suprema Food Sticks and Gammarus Shrimp Supplement and in Zoo Med Can O’ Shrimp.

The World’s Most Abundant Animal?

The Antarctic krill, Euphausia superba, may be the planet’s most numerous species…550 million tons of them are swimming in the southern Pacific Ocean at any one time (our own biomass tops out at a mere 110 million tons).  Krill form nearly 100% of the diet of certain seals, whales, birds, shrimp, squid and fishes.

Further Reading

To learn more about using freshwater shrimps, please see my article Zoo Med Canned Freshwater Shrimp.

Krill image referenced from Wikipedia and originally posted by Saperaud

Blandings Turtle image referenced from Wikipedia and originally posted by Raphael Carter.

As mentioned in Part I of this article, tiger salamander larvae (Ambystoma tigrinum), run through with a hook while alive, are still used as fishing bait in some parts of the USA.  Last time we learned about the bait trade’s role in spreading a Chitrid fungus that is decimating amphibian populations worldwide, and in hastening the extinction of endangered tiger salamanders through hybridization.

Endangered but Legally Exploited

Despite the aforementioned environmental nightmares, the bait trade in tiger salamanders remains largely unregulated, resulting in infected animals being shipped from state to state.  This practice hastens the spread of already fast-moving pathogens and of non-native salamanders, as surveys have revealed that most people and bait shops release unused larvae into local waterways.

The situation is rendered all the more bizarre by the fact that these largest of all terrestrial salamanders are critically endangered in many areas.  In fact, several subspecies, including the Eastern tiger salamander (Ambystoma tigrinum tigrinum), are protected by individual states as endangered species!

Other Threats

Tiger salamanders also face serious threats from habitat loss, pollution and the introduction of game fish to breeding ponds.  Their use of two distinct habitats – aquatic and terrestrial – renders them especially vulnerable.

Protection, when offered, is often ineffective.  In New York State, for example, 75 feet of land around breeding ponds is closed to development – but research has shown that few if any adults live within that radius!

Tiger Salamanders in Captivity

Tiger salamanders make interesting and unusually responsive captives. Longevities exceed 30 years, but captive reproduction is still somewhat problematical.  They certainly deserve more attention from hobbyists …please write in for further information.

American Bullfrogs

American bullfrogs (Rana/Lithobates catesbeianus) have also recently been implicated in spreading amphibian diseases (New Scientist: May, 2009).  Researchers monitoring food markets in NYC and California discovered that 8% of the frogs being offered for sale carried ranavirus and nearly 70% were infected with Chytrid!

Further Reading

You can learn about the natural history of the eastern tiger salamander, and the steps being taken by the NYS DEC to prevent its extinction, at

http://www.dec.ny.gov/animals/7143.html.

The Organization Amphibian Ark has taken a leading role in Chytrid research.  Read about how this fungus has caused amphibian extinctions, and predictions for the future of the epidemic, at http://www.amphibianark.org/chytrid.htm.

Image referenced from Wikipedia and originally posted by Tigershrike.

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