Feeding Prekilled vs. Live Prey
©1995 Melissa Kaplan
Myths abound when it comes to the nature, care and keeping of reptiles and amphibians. One of the most common is related to the feeding of live prey. Many people, including experienced herpetologists, herpetoculturists, pet store owners, store employees, and authors of reptile books say that reptiles and amphibians (collectively known as herps) will only eat live prey.
On the contrary. Most herps found in the pet trade can easily be converted over to feeding on killed prey, especially those herps who are already feeding on live rodents and rabbits. Reptiles and amphibians who normally feed on a variety of prey in the wild such as invertebrates, small mammals, amphibians and birds will take killed prey in captivity if offered properly. Herps whose main dietary staples include birds, fish and swimming amphibians and insects are more difficult to convert to feeding on killed and some may never do so.
The types of herps who can be easily converted to killed prey include snakes such as king, milk, gopher, pine, bull, boas, pythons (except the more difficult green tree pythons and emerald boas), corn and rat snakes. Lizards who will eat killed prey include blue-tongue and other omnivorous skinks, many of the geckos, bearded dragons, water dragons, sailfin lizards, basilisks, monitors of all types, and teiids (tegus, agamas). Large rodent-eating amphibians such as bullfrogs and ornate horned frogs will also take prekilled prey.
Why Feed Killed?
The fact, however, is that captivity is not a natural state. Our reptiles and amphibians are not spending their days searching for food, hiding from predators, searching out favored microhabitats while avoiding aggressive members of their own species, hiding, vulnerable to predation and attack, during their shed periods. Instead they are housed (or should be!) in a comfy enclosure with all of their habitat needs met. If we wanted our animals to enjoy a natural state, we would never have acquired them.
As for needing the "thrill of the kill," that is anthropomorphism at its worst. What our reptiles and amphibians need is a large enough environment outfitted properly to give it enough mental and physical stimulation. For reptiles who are handleable, handling and that opportunity to be out of their enclosure provides the exercise and stimulation that they need, not chasing a rat or mouse around a small rectangular box.
Feeding killed is also safer for the reptile or amphibian. An animal who is not hungry will not eat. It will ignore whatever is going on around it. A prey animal left alone in a tank with a predator, however, is not so relaxed about the whole thing. Mice and chicks are usually terrified, spending their time cowering in a corner or trying to find a place to hide. Rats, however, come from bolder, and hungrier, stock. If left alone long enough with a disinterested predator, they will begin to eat whatever is around: your snake or lizard. Crickets and mealworms are similarly fearless and hungry. Rats have eaten their way into snakes, devouring the skin and flesh off their backs, exposing long stretches of backbone, even quite literally eviscerating them. Even crickets and mealworms will gnaw away at the skin and seek moisture from the eyes of healthy herps when left unattended in an enclosure without proper food and moisture for them. One of the most tragic things a vet or experienced herper sees is an otherwise healthy reptile or amphibian that has to be put down or is already dead from such prey feeding practices.
Live prey may also fight back during a feeding session causing severe injuries. Claws and teeth can bite through the mouth area, puncture eyes, cut through tongue sheaths, and puncture or slice through a coil of the predator's body.
There are those who will argue that it does not happen in the wild. There are also those who will argue that it does happen in the wild and that, being a natural occurrence, should not be avoided in captivity. It does happen in the wild. We don't see much evidence of it as the injured or crippled predator manages to hide away before dying or is itself preyed upon by another predator before dying or is scavenged after dying. I responded to a call where I found a wild gopher snake whose jaw had been fractured and half its tongue bitten off by prey who had successfully fought off a feeding attempt, its grossly swollen and bloodied tongue sheath dangling from the broken, crooked jaw.
Whether it happens or not, however, is immaterial. We are responsible for the health and well-being of our animals in captivity. That means keeping them properly housed, heated, humidified and fed. And that means keeping them safe from avoidable harm.
There is, however, an easier way that is less traumatic to the mammalian prey animal, ensures immediate unconsciousness followed almost instantaneously by death. This is done by setting up a tank, be it a deep aquarium, bucket or rubber or plastic wastebasket set aside for this use, and filling it half full of carbon dioxide (CO2) gas. Once the tank is thus 'charged,' the prey animal is placed inside (be careful to not get your head too close to the tank as the gas is quite capable of knocking you unconscious, too). It is immediately rendered unconscious and is killed within a few minutes. The killed prey can then be removed (it is recommended that you use long kitchen or barbecue tongs), and set aside to be fed out or frozen for later use. Let the gas dissipate outside by setting the tank outside for a couple of hours.
You can get CO2 relatively inexpensively in a gaseous form in tanks from welder's supply shops, and in solid form (as dry ice) from ice houses; these suppliers may be found in the telephone yellow pages.
Sources of Killed
While some people have no problem with the feeding of prey and are interested in feeding killed prey, they may not be able to do it themselves. An increasing number of pet stores are selling prekilled prey or may kill upon request. If you have a large number of reptiles or just a few big eaters, there are many mail order prey suppliers who ship out bulk orders of frozen prey. Their prices are less expensive than pet store prices, even when adding in the cost of shipping. It takes much less room to store 100 frozen adult mice in your freezer than it does to house, feed and care for properly the same number of live mice. Buying frozen can save you enough money to enable you to provide better care and housing for your herp, or even to acquire another one.
If you breed your own or acquire large quantities of live mice, rats or rabbits, you can set up a mini-gas chamber to quickly euthanize the prey. By 'charging' a deep enclosure, such as a tall aquarium or a clean garbage can, with carbon dioxide (CO2), and then placing the prey inside, they are killed almost instantaneously, being rendered unconscious when they hit the gas. (Note: you cannot euthanize reptiles or amphibians this way as their oxygen metabolism is very different and they can live surprising long periods of time in an oxygen deficient atmosphere.) Gassed prey should be frozen for several weeks before feeding out. This will dissipate any gas in the tissues (which some people feel may be harmful based on experience with birds of prey freshly gassed rodents) and will kill any parasites in the rodents.
Freezing for 30 days kills off most parasites and other organisms that may be harmful to your herp. Prey may be kept safely frozen and fed out for up to six months after the date it was first frozen.
Remove the number of prey items you need from the bag of prey. You can place them in a clean plastic bag and soak in warm water, or leave in the refrigerator overnight to defrost, warming up in warm water. If you are skilled with your microwave, larger prey may be defrosted and gently heated using the defrost setting or lower power settings. Small pinkies can be quickly defrosted and warmed by holding under warm running water, or in a bag on top of a warm surface, such as the stove-top over the pilot light.
Always make sure that not only is the frozen prey thoroughly defrosted but that it is warmed up to a temperature above room temperature. You do not want your warm reptile eating cold prey, and warming the prey also makes it smell more strongly, and thus more attractive, to your reptile, and may be especially important when feeding reluctant feeders and when in the process of converting live feeders to killed.
Feeders to Eating Killed
Eaters to Rodent Prey
A suitable food such as a frog or lizard should be obtained and humanely euthanized for feeding. Instead of feeding it out, however, the lizard or frog should be rubbed all over a suitably sized prekilled mouse or rat to scent it. The scented rodent is then offered for feeding.
Another method is to pith (stick a pin or small nail) into the brain case of a killed rodent; this intensifies the scent and may attract a reluctant feeder into feeding.
For other suggestions on how convert to feeding killed rodents or to get reluctant feeders feeding, contact your local herpetological society.
For information on euthanizing reptiles, please see Stephen Barten DVM's article on euthanasia and my note on the inappropriateness of decapitation as a method of euthanization of reptiles. Also available are excerpts from reptile care texts on feeding prekilled, Reptile Veterinarians and Curators on Feeding Rodent Prey, with some photos of chewed-up snakes.
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