Conducting scientific experiments on animals has long been a point of argument among members of the scientific community, among individuals in other professions, and between the scientific community and the general populace. Is it ethical to subject animals to tests that we cannot be certain on the results of? What if the animals suffer ill effects? But if we don’t conduct such tests, how can we make scientific advancements? The exact ethics are still debated, but, generally, people have excepted the necessity of some animal testing.

Mice: The Perfect Test Subjects?

Few things are cuter than baby mice, and few animals make better test subjects for scientists than mice do. There are a number of reasons we use mice to conduct animal testing, but they lean more towards the practical than the purely scientific. The small size of mice makes them very easy to keep the necessary numbers on hand, ensures they are easy to manage (unless you drop one), and keeps the cost of animal food down.

However, scientists don’t perform their experiments on mice just for the ease, there are some specifics about mice that make them more suited for scientific testing than other small animals would be. The simplest criterion is just that mice are mammals. There are plenty of small, light-eating, harmless creatures out there in the world, but the majority are insects, fish, etc. These animals just don’t have enough in common with human beings to be of much use in most testing. What about other small rodents then? Well, some other species are used on occasion, but they tend to be larger, eat more, be more dangerous, slower to reproduce, etc.

Mice are especially suited to be used in scientific experimentation, even over other seemingly-suitable animals, for a few key reasons. First, mice and humans share 90% of our DNA. This helps scientists be certain of how a change will affect human genes, by seeing what they do to a mouse’s. Mice are also relatively easy to manipulate genetically, making genetic experiments easier and cheaper to perform. “Knockout” mice are mice that have specifically had certain genes turned off, usually to study how genetic factors affect diseases. “Transgenic” mice have been bred with additional DNA that is foreign to their natural structure. These can be used for a greater variety of experiments.

Caring For And Rewarding Our Little Subjects

Some people condemn scientists who perform experiments on mice, or any animals, stating that the animals are not treated well, that the animals suffer too much to make any advancement worth it. However, mice that are used for scientific experimentation are actually very well cared for, in most cases. While it is, sadly, true that some experiments cause trouble for their subjects, any such suffering is kept as minimal as possible, and the mice are treated well the rest of the time.

There are numerous oversights in place to ensure that all animal test subjects are cared for and suffer as little, at all, as possible. The largest body overseeing the treatment of such animals in the United States is the Animal Welfare Act put in place by the National Academy of Sciences, This act made the ethical treatment of animal test subjects a matter of federal law. There are other committees and governing bodies as well, in the US and globally.

The “Three R’s” is the most important set of guiding principals set in place to ensure the ethical treatment of test animals. The “Three R’s” are replacement, reduction, and refinement. The replacement principal states that, whenever possible, another means besides animal testing should be used. This included computer modeling and other simulations. Reduction says that scientists need to use methods that require as few animal subjects as possible while still getting accurate data. Finally, the refinement principal guides scientists to design their experiments to expose their subjects to as little suffering as they possibly can.


Mice have been used in a great variety of scientific experiments, but some of the most interesting experiments conducted with the aid of these little creatures have involved sending them into space! Human beings are not the only creatures to exist in space anymore, the International Space Station boasts its own small population of mice. These little fellows were sent up there (and reproduce there) to be used in all sorts of experiments involving the unique conditions that exist off the surface of our planet.

Recent studies have shown that mice adapt to conditions of microgravity with ease, but also take on some odd behaviors. Mice that have lived in the very low gravity on the space station long enough to adapt to it are prone to zip around and around their cages, running on the walls! Some experiments have been done on mice in space before, but these experiments are the first to last long enough to show how mice adapt to these conditions.

April Ronca, a scientist at the NASA Ames Research Center down here on planet Earth (in Moffet, California), used data sent back from the NASA Rodent Habitat on the Internation Space Station to study the effects of many conditions experienced by astronauts, including microgravity. Other conditions studied include exposure to radiation, higher levels of carbon dioxide, and prolonged confinement. This study included using videos set up inside the NASA Rodent Habitat to visually track the behavior of the mousetranauts, which led to the discovery of the odd “circling” behavior of the mice running around their cages.