After decades of serving medical research, the government-sponsored Laboratory chimps are all set to retire. (Photo: Reuters)

The U.S. government will retire over 300 laboratory chimpanzees over the next few years. The announcement of the chimps' retirement came Wednesday from the National Institutes of Health, or NIH. The institute cited the need to usher in a "compassionate era" with humanity's closest animal relative, who for decades the government has used for medical research.

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"Chimpanzees are very special animals ... We believe they deserve special consideration," said NIH Director Dr. Francis Collins. "These amazing animals have taught us a great deal already."

AP reports that 50 chimps will be held on retainer just in case a situation arises that would call for immediate and emergency animal testing.

The 310 chimpanzees to be retired will end up in animal sanctuaries across the U.S., where they will no longer be cooped up in research facilities and will be able to socialize with other chimps. Animal rights groups lauded the NIH's decision to release the chimps from scientists' custody.

"This is an historic moment and major turning point for chimpanzees in laboratories -- some who have been languishing in concrete housing for over 50 years," said Wayne Pacelle, CEO of the Humane Society of the United States.

Not everyone is happy about the NIH's decision to disband its research chimp reserve, however. Reuters reports that the Texas Biomedical Research Institute, an independent group, said it was disappointed in the government's plan. In a statement, the organization called the decision "arbitrary" and said that chimps are necessary for finding cures for hepatitis B and C, which the institute says kill a million people every year.

Of course, animal testing is a contentious issue. The debate about medical testing on chimpanzees revolves around the long term emotional and physical toll it can take on the animals. According to The Real News, research chimps often exhibit signs of depression and distress. Caged chimps have been known to develop unhealthy ticks like hair plucking and self-mutilation.

On the other end of the spectrum, researchers cite the chimpanzee's usefulness in advancing medical science. Dr. Sally Rockey, the NIH deputy director for extramural research, told The Real News chimps have played a key role in AIDS research and development.

"I think everybody recognizes that if we had an alternative model we would be using it," Rockey said. "Since it is the only model we have now, it's crucial that we continue."

Chimpanzees are humans closest living relatives and share 98 percent of their genetic blueprint with us. Also like us, chimps are social creatures and live in communities of several dozen animals. They are one of the few animal species that employ tools, and can shape sticks to fetch insects from their nests or to dig grubs out of logs.

The U.S. is the world's number one user of laboratory chimpanzees with roughly 1,200 individual animals currently in U.S. laboratories. According to Save The Chimps, a nonprofit animal sanctuary that cares for former laboratory chimps, most of the captive chimps in the U.S. are kept in biomedical research labs. U.S. psychologists first started studying chimps in the 1920s, and by the 1940s, chimpanzees were widely viewed as ideal medical research subjects. Fifty years later, there were as many as 1,500 chimpanzees living in at least 11 various research facilities across the U.S.

When the AIDS epidemic cropped up in the 1980s, scientists looked to chimpanzees as test subjects for the new, deadly disease. More recently, however, there has been a decline in the number of laboratory chimps in the U.S. From Save The Chimps:

By 2000, the use of chimps in biomedical research began to see a decline, although their use as models for hepatitis C research continued to interest scientists. Over the past decade there has been a modest decline in the estimated number of chimps in living in research laboratories, from 1500 to 1100, largely attributed to the transfer of chimps from labs to sanctuaries such as Save the Chimps, as well as deaths of chimps in labs and an overall reduction in breeding.

In 2011, the U.S. Institute of Medicine declared that the use of chimpanzees for biomedical research was superfluous and should be curtailed. In a report, the institute recommended applying strict scrutiny when deciding whether or not to use chimps in medical testing. It said chimps should only be used if there is "no other suitable model available, such as in vitro, non-human in vivo, or other models," for the research in question, and that chimpanzees should only be tested if the research cannot be performed ethically on human subjects.

See what happens when laboratory chimps see the sky for the first time:

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