Educational Series: Rodents Are Intelligent, Sensitive Animals, Not Fodder for Experiments

Animal research labs–where scientists perform experiments on living creatures to develop products or procedures for use on humans–have long been a major focus for animal welfare advocates. Images of monkeys and apes in tiny cages, dogs forced to undergo painful operations, or cats being injected with chemicals are almost certain to bring up feelings of disgust or fury in any person sympathetic to the well-being of animals. As a result, research labs have come under increasing public scrutiny over the course of the last several decades–yet, much of this needed attention has neglected the species used in the vast majority of experiments.

While public concern about lab animals tends to focus on dogs, cats, and primates, researchers far more commonly experiment on rodents. Calculations of exactly how many mice, rats, and other rodents are subjected to research annually in the United States vary widely. On the lower end, organizations like Speaking of Research, which supports using animals for science, estimates U.S. labs experiment on 10-25 million rodents per year–the vast majority of them mice and rats. In contrast, a recent study by animal welfare scholar Larry Carbone used data collected by surveying large research institutions to put the number at about 111 million.

Clearly, the difference between 10 million and 111 million is huge–more than a 100-fold increase. It is difficult to arrive at more exact figures, because labs in the U.S. are not required to keep detailed records of how many rodents they use. However, even the more conservative estimates put the proportion of mice, rats, and their kin used for research at over 90% of all lab animals; if Carbone’s study is correct, the number rises to more than 99%. In other words, no one seriously disputes that rodents far outnumber all other animals used for laboratory research in the United States.

Why do rodents dominate in research to such a large degree? To begin with, they are small, easy to raise in captivity, and reproduce quickly. This means labs can quickly obtain large numbers of new rodents to experiment on simply by breeding more. Because of rodents’ short reproductive cycles, scientists studying problems in genetics can trace how information is passed from one generation to another on a shorter timescale than would be possible with most other mammals. And since rodents like mice and rats are indiscriminate omnivores, they are easy to feed and keep alive cheaply. But just as importantly, scientists have long argued that rodents share a number of natural traits that make them ideal research subjects.

One of the first species to gain notoriety as a research animal was the guinea pig, so much so that its use in experiments gave rise to a widespread cliche. The plump, furry rodents, which were domesticated thousands of years ago in South America, have less natural disease resistance than many wild animals, and this has made them popular with researchers for more than a century.. Scientific breakthroughs credited to early research on guinea pigs include the discovery of Vitamin C and the isolation of the bacterium that causes tuberculosis. However, what is usually left out of the story is the suffering undergone by these and other rodents subjected to lab experiments–even now, when alternatives to animal research are much more widely available than they were a hundred or even twenty years ago.

Today, guinea pigs are still commonly used as subjects for research on the effects of cigarette smoke, alcohol, infectious diseases, and pain. According to the American Anti-Vivisection Society, guinea pigs as well as hamsters are among the species most often used for experiments that cause significant amounts of pain to the animals involved. At same time, the importance of guinea pigs in research has been eclipsed over the last several decades by an explosion of studies focused on other rodent species.

Rats and mice now compose the vast majority of rodents used by labs in the United States–and their popularity with researchers has likely only been increased by the fact that they are not protected under the U.S. Animal Welfare Act (AWA). Although the modern version of the AWA was meant to apply to all warm-blooded animals when it passed in 1970, enforcement of protections for mice and rats was long stymied by a lack of funding. In 2002, Congress officially amended the AWA to exclude these species as well as birds. In short, while cats, dogs, primates, and even guinea pigs and hamsters receive at least a nominal form of protection from cruel practices under U.S. federal law, the same cannot be said of the animals used in more than 90% of all research experiments.

Despite their ubiquity, it seems safe to say lab rats and mice have not received as much attention from the public–or even many animal rights groups–partly because they are less charismatic and elicit less sympathy from most people. Yet, science itself reveals that rodents are intelligent and sensitive creatures with needs similar to those of other mammals.

Rats, in particular, are fast learners and display traits normally associated with high animal intelligence. They are naturally social creatures who need the company of other members of their species, and have even been observed trying to help other rats in need in what can only be described as a display of empathy. Rats have also shown themselves to be capable of metacognition, an ability that involves remembering information learned during prior experiences and applying it to a new situation. Finally, and unsurprisingly for such smart creatures, rats require a mentally stimulating environment to stay healthy. Rats in captivity should have access to tunnels, perches, toys, or other objects that let them practice their propensity for exploring and experimenting with their environment. Sadly, though, most lab rats live out their lives in small, barren cages.

Ironically, conditions that cause suffering in lab rodents may actually be leading to poorer research results. Mice, rats, and guinea pigs are used for research partly because they are in many ways genetically and physiologically similar to humans; but the commonalities only run so deep, and may be undermined by the sedentary lifestyle forced on lab animals. Some researchers have found that rodents who get little to no exercise and are deprived of mental stimulation are less likely to respond to changes in diet in the same way that a healthy, active human would. This means there is an argument for treating lab animals better even apart from ethical considerations.

Discussions about the use of animals in research often refer to the “three R’s”: reducing the frequency with which animals are used in experiments, finding replacements for animals in research wherever possible, and refining research methods to protect the subjects from unnecessary physical or emotional pain. One way to accomplish the first “R” is to end the use of rodents and other animals in the development of cosmetics which serve no truly necessary purpose. In our modern age, technological substitutes often render animals unnecessary even for important medical research. And while eliminating the use of animals is always better, improving lab environments to give rodents ample space and stimulation can reduce pain and suffering in the meantime.

The prevalence of rodents in research means it is impossible to address the ethical issues surrounding animal laboratories without focusing on the needs of mice, rats, and their relatives. Furthermore, the intelligence of these small mammals leaves no room for doubt about their capacity for feeling mental and physical pain. The good news is that with enough help from dedicated animal lovers, millions of rodents can be saved from lives of cruelty and torture–and now is the time to give them the attention they deserve.

Photo credit: Global Panorama

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What percentage of animals used in lab research are rodents?
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Which behavior has been documented in rats?
True or false: Depriving rodents of exercise and stimulation can lead to less useful research results
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Nick Engelfried Writes About Animals, the Environment, and Conservation for the ForceChange network

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