How many animals are used in experiments each year?

It is estimated that more than 50 million animals are used in experiments each year in the United States. Unfortunately, no accurate figures are available to determine precisely how many animals are used in experiments in the U.S. or worldwide.

The U.S. Department of Agriculture (USDA) does compile annual statistics on some animals used in experiments, including cats, dogs, guinea pigs, hamsters, pigs, primates, rabbits and sheep.

However, the animals most commonly used in experiments—“purpose-bred” mice and rats (mice and rats bred specifically to be used in experiments)—are not counted in annual USDA statistics and are not afforded the minimal protections provided by the Animal Welfare Act. The Animal Welfare Act is a federal law that sets minimal standards for the treatment of certain warm-blooded animals used in experiments. The law also requires that unannounced inspections of all regulated animal testing facilities are carried out annually, although some facilities only receive partial inspections. In addition to purpose-bred mice and rats, animals such as crabs, fish, frogs, octopuses and turtles, as well as purpose-bred birds, are not covered by the Animal Welfare Act. The failure to protect these animals under the law means that there is no oversight or scrutiny of their treatment in the laboratory or the experiments performed on them. And, because these animals are not counted, no one knows how many of them are suffering in laboratories. It also means that facilities using unprotected species in experiments are not required to search for alternative, non-animal methods that could be used to replace or reduce harmful experiments that use animals.

Which animals are used in experiments?

Animals used in experiments include baboons, cats, cows, dogs, ferrets, fish, frogs, guinea pigs, hamsters, horses, llamas, mice, monkeys (such as marmosets and macaques), owls, pigs, quail, rabbits, rats and sheep.

Chimpanzees have thankfully not been subjected to invasive experiments in the U.S. since 2015, when federal decisions were made to prevent their use. Despite this, hundreds of chimpanzees are still languishing in laboratories while they wait to be moved to sanctuaries.

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What kinds of experiments are animals used in?

Animals are used in many different kinds of experiments. These are just a few examples:

• Dogs have their hearts, lungs or kidneys deliberately damaged or removed to study how experimental substances might affect human organ function.  
• Monkeys are taken from their mothers as infants to study how extreme stress might affect human behavior.
• Mice are force-fed daily doses of a chemical for two years to see if it might cause cancer in humans.
• Cats have their spinal cords damaged and are forced to run on treadmills to study how nerve activity might affect human limb movement.
• Ferrets are deliberately infected with extremely painful, potentially fatal diseases (such as RSV, COVID-19 or Ebola) and not given pain relief or treatment before their death to study how humans might be affected by the same disease.  
• Pigs are implanted with various devices (such as pacemakers and dental implants) to study how human bodies might respond to such devices.  
• Pregnant rabbits are force-fed toxic pesticides every day for several weeks to study how human mothers and babies might be affected if they were exposed to the pesticides.
• Sheep are subjected to high pressures (such as those experienced deep underwater) for hours at a time and then returned to normal pressure so that their response can be observed.
• Rats are placed in small tubes and are forced to inhale cigarette smoke for hours at a time to study how humans might respond to cigarette smoke.   
• Baboons are injected with endometrial tissue to induce painful symptoms of endometriosis and study how humans might be affected by the disorder.
• Horses are infected with a potentially fatal virus (such as hepatitis) and their symptoms monitored to study how humans might be affected by the same virus.

Experiments are often excruciatingly painful for the animals used and can vary in duration from days to months to years. The experiment can cause vomiting, diarrhea, irritation, rashes, bleeding, loss of appetite, weight loss, convulsions, respiratory distress, salivation, paralysis, lethargy, bleeding, organ abnormalities, tumors, heart failure, liver disease, cancer and death.

There is no limit to the extent of pain and suffering that can be inflicted on animals during experiments. In some instances, animals are not given any kind of pain medication to help relieve their suffering or distress during or after the experiment on the basis that it could affect the experiment.

Animals are typically killed once an experiment is over so that their tissues and organs can be examined, although it is not unusual for animals to be used in multiple experiments over many years. There are no accurate statistics available on how many animals are killed in laboratories every year.

Where do laboratories get the animals they use in experiments?

The majority of animals in laboratories are “purpose-bred” meaning that they are bred specifically to be used in experiments. People who breed and sell certain purpose-bred animals are called Class A dealers and are licensed and inspected by the U.S. Department of Agriculture (USDA). Facilities that only sell purpose-bred mice, rats, birds or cold-blooded animals such as crabs, fish, frogs, octopuses and turtles to laboratories are excluded and are not licensed or inspected by the USDA.

Some animals used in experiments are taken from the wild—including birds and monkeys. 

Historically, some cats and dogs were sold to laboratories by brokers known as random source Class B dealers, who acquired animals at auctions, from newspaper ads and various other sources, including animal shelters. Random source Class B dealers have not been allowed to operate since 2015 when Congress first passed legislation to prevent them from being licensed.  

Some cats and dogs in laboratories are still obtained directly from animal shelters, a practice known as “pound seizure.” Pound seizure laws vary from state to state with one state (Oklahoma) requiring shelters to give cats and dogs to laboratories, rather than euthanizing them, and others allowing or prohibiting laboratories from taking animals from animal shelters. Some states have no laws at all, leaving it up to the individual shelter or locality.