The use of animals in lab experiments had been on the rise in the U.S., despite growing public opposition and evidence that animal studies do not always translate to humans.

The shocking findings contradict industry claims that labs are working to reduce animal testing and experimentation, the Journal of Medical Ethics reported. There are federal guidelines in place that work to reduce and replace animals in lab experiments, but these policies focus more on larger animals and tend to ignore common lab species such as mice, rats, reptiles, and birds. These exclusions have led to a significant absence of published data outlining how many of these types of animals are really used for experimentation.

People for the Ethical Treatment of Animals (PETA) filed Freedom of Information requests to reveal some of this unpublished data on the use of vertebrate species at the top 25 universities that received research grants.  They found the use of animals in labs rose 73 percent between the years of 1997 and 2012. The rise was mostly seen among mice, while the number of many other species used in labs remained unchanged. The findings also revealed unregulated species made up 98.8 percent of the animals used in the observed labs.

This study marks the first time data on the rising trends in lab animal use in the U.S. have been published. The findings call attention to the need for more efforts to be taken in reducing the amount of animals used in labs, as well as increase transparency in reporting the success of these efforts. A linked viewpoint discusses the tension between scientists and animal rights activists, and suggests those on both sides are actively working to see the other's point of view.

"It recommends that institutional policies be updated to better inform the public about the use of animals in scientific research, as well as opening up dialogue between a broad base of players to replace the current often poorly informed and emotionally charged debate," the researchers stated.

The findings were published in a recent edition of the Journal of Medical Ethics.