Rats and mice are considered vermin when they live in their natural habitats and compete with humans for resources. Our urge to kill them gave us domesticated cats, and we are grateful for that. However, those vermin also help us test scientific ideas, including drugs and other medical breakthroughs. The very traits that cause them to plague humanity are the traits that make them good experimental subjects.
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“They reproduce quickly, they are social, they are adaptable, and they are omnivores, so they’ll eat pretty much anything,” says Manuel Berdoy, a zoologist from Oxford University. Additionally, the rodents’ diminutive size allows relatively easy storage in labs, and their shared evolutionary roots with humans mean the species’ genomes overlap overwhelmingly.
As a result, rodents have all but taken over our labs, making up nearly 95 percent of all laboratory animals. Over the past four decades, the number of studies using mice and rats more than quadrupled, while the number of published papers about dogs, cats and rabbits has remained fairly constant. By 2009, mice alone were responsible for three times as many research papers as zebra fish, fruit flies and roundworms combined.
Studies with rodents address everything from neurology and psychology to drugs and disease. Researchers have implanted electronics into mice brains to control their movements, repeatedly tested the addictive properties of cocaine on mice, administered electric shocks to rodents as a negative stimulus, implanted human brains in mice skulls, and sent mice and rats scurrying through endless labyrinths of tests. NASA even keeps lab mice aboard the International Space Station for experiments in microgravity.
The US Animal Welfare Act covers most laboratory animals, but excludes rats and mice. Still, there are guidelines in place that attempt to reduce unnecessary stress and pain in lab rats. Read about the history of laboratory rats at Smithsonian.
(Image credit: Anna Marchenkova)