Feeder mice are mice that are raised specifically to be fed to other animals, mostly pet snakes, carnivorous lizards such as tegus and savannah monitors, some turtles and amphibians. Feeders are different from mice that have been raised to become pets. Unlike those, feeders are usually mixed breeds, and are not bred for good temperament, conformation or longevity. There are, however, some characteristics and other points that you'll want to seriously consider when purchasing feeder mice for your pet exotic.
Decide if live feeder mice are appropriate for your pet's diet. Live mice are often a poor choice for many reptiles or amphibians because they fight back and will attack your pet while being eaten. If your pet isn't hungry, it may ignore a live feeder mouse, which is almost certain to bite or chew on your pet. This is very dangerous as the animal could contract a serious illness, even resulting in death, from the bite of a feeder. Either give frozen food, or buy feeder mice alive and kill or stun them before offering them to your pet. You also can kill and freeze them.
Locate some sources from which to buy your live feeder mice from. Most pet stores carry them, but be aware that many shops will refuse to sell their live pet mice for food. Read the ads in specialty snake, lizard, turtle or amphibian magazines. Many retailers offer live and frozen feeder mice and advertise in these periodicals. Feeder mice also can be purchased online.
Take a few moments to observe the live feeder mice you're considering. They should be very active. Don't take any that are sluggish, hiding in a corner, running in circles or excessively scratching themselves. Look for sleek, smooth coats with no visible sores or bumps on the bodies. Select feeder mice with thick tails, which is an indication that they are healthy enough to eat well. If the cages are dirty or very smelly, choose a different supplier. It probably isn't the best idea to order feeder mice sight unseen, as you won't know what you're getting until you get them.
Choose feeder mice of a size appropriate for your pet. With snakes, choose feeder mice with bodies no bigger than the snake's girth size. Feeding it mice that are too large will cause the snake to regurgitate. For lizards, the prey should be two-thirds the length of the head. Turtles and amphibians should be fed feeder mice that are no larger than their heads.