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

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.

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