To some people the title of this page may be rather off-putting and in fact sound "worse" than it really is. Let me clear up a couple of things first:
1. The use of live rodents to be offered as food to reptiles and amphibians is nowadays strongly discouraged for various reasons, not least the danger to the would-be predators themselves. While large monitor lizards will usually quickly strike and devour living prey, snakes have been known to actually ignore a mouse or rat in their vivarium and fall asleep, with serious or even fatal consequences as the rodent then gnaws on the snake. Rats in particularly are pugnacious fighters if cornered, and even if the predator emerges "victorious", it may suffer unpleasant injuries. Whilst this is normal in the wild, it is undesirable for captive animals if unnecessary, as it usually is. All but the most finicky or unusual herptiles will just as soon eat a prekilled rodent as a live one.
2. Hobbyists do not need to gather and/or kill rodents before feeding them
to their pets. Instead, frozen rodents of various types and sizes can be purchased
from most pet shops that have a refrigerator. All professional establishments
that deal with the preparation of such food prior to shipping it out to the
retailers are obliged by law to kill it humanely according to a set of government-dictated
guidelines. The use of CO2 is apparently the preferred method.
The nutritional value of rodents is fairly high in terms of calcium. In addition, unlike meat eaten by humans, who tend to take the tastiest parts of an animal and leave the rest, a herp will eat the entire animal, including such parts as the internal organs which have nutritional value of their own, and the bones. No part of the animal is left uneaten.
The most commonly used rodent for feeding reptiles and amphibians is the ordinary mouse as bred in laboratories for many years. These come in various sizes according to the age of the animal when euthanised.
Pinkies are probably the most commonly used, and smallest, size, being young mice that have been killed when still nestlings. These are pink (hence the common name) and almost hairless, and about half the length of an adult human's thumb. These can be fed as a regular diet to most colubrid snakes such as corn snakes, milk snakes, kingsnakes and rat snakes, and as an occasional treat to lizards ranging in size from large geckos such as leopards and tokays upwards to bearded dragons, plated lizards, the larger skinks and the like. A few amphibians, such as the voracious Ceratophrys frog species or large salamanders like the Tiger Salamander, will take the occasional pink. Thawing time for one of these from frozen is about 30-45 minutes in a container of cold water.
Fluffs are the next size up, being juvenile mice that have usually, though not always, grown their fur (hence the name). These are useful for feeding larger colubrid snakes, smaller pythons and boas, and adult-sized carnivorous lizards such as tegus or monitors. Thawing time is 60-75 minutes.
Rat pups are similarly the nestling young of adult rats, but tend to be the
same size as fluffs but without the fur. Thawing time is about the same as for
fluffs. They can be fed to much the same sort of animal.
The next sizes up tend to be adult mice, followed by adult rats. This sort of size is reserved for the very largest lizards (eg, full-grown tegus or large monitors such as Niles or Water Monitors) and boas and pythons. I have no idea of the thawing time, having never used these myself, but suggest 2 hours.
Finally we come to the very largest common prey items, rabbits. These are euthanised humanely in the same manner as rodents but understandably are not so common in the shops. However, most specialists will be able to get hold of them. As a rule the consumption of these relatively large food items tends to be confined to giant constrictors, in practice the four largest (Burmese, African Rock, Reticulated and Anaconda). These are items that the keeper might want to thaw out overnight before offering the next day: beware, however, of leaving them in the same room as the snake while defrosting, as the smell of food can trigger off some unpredictable reactions in these giants.
A word or two is in order here about chicks. I believe these are more
commonly offered to birds of prey, but some large herps such as monitors may
take them, depending on the size. Certainly some lizards will feed on them as
eagerly as on rodents, and there is evidence that for some monitors at least
this is a preferable food to rodents. The chicks are usually just that - chicken
offspring - and can be thawed out in a couple of hours or so.
As with frozen food for human consumption, frozen rodents and the like should be kept in the freezer, or at least in the fridge if the entire quantity you have is to be eaten within a few days. The freezer is however preferable as they will keep longer that way.
Obviously a few precautions need to be taken. Firstly, ask the owner of the
freezer if they are amenable to this. Otherwise your mother or spouse will not
be pleased to open up an innocuous paper bag and find a bunch of dead mice inside
it - such incidents rarely show herpetology in a good light. Secondly, keep
the food items in a separate container from all other food, and preferably on
a separate shelf. While I have not seen any evidence to suggest that storing
frozen rodents is somehow detrimental, even slightly, to human health, it pays
to be sensible. A large number of pinkies can be stored in a tupperware container
or old ice-cream tub which can then be labelled accordingly. Even storage in
a plastic or paper bag, however, is okay if the bag is sealed. Our own arrangement
is that we keep all food for the animals on a separate shelf in our freezer.
There seems to be a certain limited shelf life to frozen food, even if kept
in a freezer, just as there is to meat for human consumption. I have noticed
that after a few months in the fridge, frozen rodents tend to become discoloured.
This may not be harmful to the recipient, but it is better not to take chances.
Often frozen food for humans has a three month maximum suggested after which
it should be binned, and I would suggest the same for frozen rodents. It pays
therefore to keep stock of the supply you have in the freezer and run down old
supplies before buying any more, or you may end up with a quantity of discoloured
feed items in the back of your freezer that should probably be thrown out.
Obviously frozen food needs to be thawed out before being offered to reptiles and amphibians (or any creature). One thing must be made clear: the use of microwave ovens to defrost this sort of food is strongly discouraged. Even human food is patchy in its results in microwaves, and a number of writers have stated that microwaving frozen food items produces uneven results and leaves "cold spots" inside them that are still unthawed despite appearances. It may be quick, but it certainly is not safe. Given the known unpleasant effects of badly-defrosted food on human beings, you should avoid microwave ovens.
The best method I have found for safely defrosting frozen food items is the
use of a tupperware or similar plastic container filled with cold tap water
(or bottled water if the tap water in your area is not considered safe to drink).
Leave the food items in the water for the suggested thawing time and then fish
them out, give them a shake to remove excess water and add any vitamin/calcium
supplement as necessary.
For actually offering dead rodents and the like to herps I prefer to use a pair
of tongs rather than my fingers, even if the recipient is a gecko or similar
small herp. This is because many herptiles tend to lunge at a rodent and seize
it avidly, often catching human fingers in the process. Also, as some herps,
particularly amphibians, seem to need to see moving prey, you may have to wiggle
the rodent a little to attract the recipient's attention. This is safer and
easier with tongs. Offering food items from your fingers to large monitors or
similar lizards and even more so to large constricting snakes should not even
be considered in most cases. The only alternative is to lay the food items on
a dish, rock or similar area in the cage and hope that the recipient will find
and eat them. This works for many reptiles (especially monitors and snakes)
and is the safer procedure with some very large animals, but may not be so good
for those amphibians which need movement to find prey. You should check available
literature or the Internet for suggested feeding procedures for your own species
of pet(s).
While rodents and other such food items make good meals for herps, they are not to be over-used. Most snakes and large monitors can probably exist on a diet largely of these creatures as they do in the wild, but caution is called for with most other herps. This is because in the wild, most lizards and amphibians are insectivorous (insect-eaters) rather than carnivorous (flesh eaters). For these animals, rodents may be an occasional beneficial treat, but if offered regularly in place of their normal diet can cause a build up of fat or excessive calcium, either of which most herptiles are ill-equipped to deal with. Even many monitors will only eat rodents as part of a diet, making up the rest with fish, molluscs and insects. Therefore we repeat: check out the suggested diet for your herp(s) and offer rodents in the right proportions, if at all. Herbivorous reptiles such as iguanas and many tortoises should never be offered such food.
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