Feeder mice are bred in facilities for the express purpose of feeding to predatory animals, such as snakes or large birds. They are usually given standardized diets and access to fresh air and water to ensure their healthfulness to the animals that will eventually eat them. Most mice bred in laboratories and feeding facilities are descended from the common house mouse, Mus musculus.
Because feeder mice serve as food for a large array of different predatory pets, they come in many different sizes. These range from hairless 1-day-olds and “pinkies,” which are still mostly hairless and between 2 and 5 days old, through to “fuzzy” feeder mice, which are starting to grow in their hair and are between 6 and 14 days old. Hopper, small, medium, large and jumbo are the next sizes up, as mice get larger with age. Usually you can get a discount for buying feeder mice in bulk.
Many mice are flash-frozen for feeding purposes. This is a more humane way for the animal to die, which appeals to many people, and also minimizes the chance that prey will fight back and damage the predator. Additionally, mice are frozen with their tails and feet tucked in for easy packaging and freezer storage. This also makes it easier for the snake to swallow it. Because they were frozen quickly and are usually shipped immediately after freezing, they retain much of their original nutritional value.
Snakes feed on live food, which is why many owners prefer to give them live prey such as feeder mice. However, it is arguably more humane to feed snakes with pre-killed mice, so many owners choose to take this route. When opting for this, you may need to teach your snake to tolerate dead food by rubbing it with the mucous of its preferred food (such as frogs or toads), thawing and warming it, or dangling it in front of the snake to simulate movement until it displays interest.
Fancy mice are different from feeder mice in that they are bred to serve as companions to humans. Like rats, mice are social creatures that make for good pets if trained from a young age. They have different personalities, enjoy spending time with one another and humans, and, though timid, can be trained to like handling. Many owners also enjoy simply watching them in their cages. Unlike feeder mice, in which color does not matter, fancy mice come in a variety of colors and patterns.
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Sarah Moore has been a writer, editor and blogger since 2006. She holds a master's degree in journalism.