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, the killing of animals other than the species that is the target of a pesticide, is an important concern whenever toxins are used.
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.
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.
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.
Please see my article Collecting Invertebrates: an Entomologist’s Technique and the articles referenced there for further information.
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