In a laboratory in Ohio, People for the Ethical Treatment of Animals say beagles were force-fed the painkiller Oxycontin.
It happens across the U.S., but at least two beagles in California managed to get away. Bigsby and Freedom survived years of experimentation at a research facility in Northern California until they were saved by Shannon Keith. The activist and animal rights attorney won't say which facility she saved them from. Keith hopes by keeping the lab's name out of the news, more beagles will be voluntarily released alive.
"I jumped at the chance to save them," she said. "It is a university, it is in California and these particular beagles were subjected to toxicity tests."
Both beagles were silenced - debarked - by the breeder who sold them to the lab.
"While being restrained, poked, prodded and generally tortured, they don't scream in pain, don't bark and don't bother the technicians," Keith said.
A tattoo of the dog's federal I.D. number can be seen on each ear.
Kimberly Dreher is Freedom's new owner. She says life outside the lab has been an adjustment.
"It's just awful that he used to be known by a number," she said. "He's learning how to play fetch. So at first, he didn't even know what a ball was, I'd throw it and he'd just kind of look at it, like 'What are you doing? What is that?'"
So how common is animal research on dogs, cats and even monkeys? The numbers are surprising. According to the United States Department of Agriculture, 75,000 dogs, 21,000 cats and 124,000 non-human primates like monkeys were used nationwide in 2009.
"I'm not a terrorist," Vlasak said. "I don't think I've inflicted terror on anybody who didn't deserve to have terror inflicted on them."
Vlasak compares animal rights to the U.S. Civil Rights movement and says murder may be justified to stop animal experimentation.
"All of these successful liberation struggles have always involved violence or the threat of violence," he said. "I would hope that hurting, killing or assassinating would not be necessary. I would say it would be morally justified if all other methods failed."
For that reason, FBI special agent Steven Gomez says the AFL is a threat.
"They're very dangerous because they're intelligent and sophisticated, based on the attacks and devices," Gomez said. "They know what they're doing and they're very committed to what they're doing."
A top target of animal activists is Dr. David Jentsch, a neuro-scientist at the University of California, Los Angeles, who studies the biology of mental illness and addiction.
"Monkeys are euthanized because of this research, that's harm done," Jentsch said, "but I can't ignore the millions of preventable deaths that biomedicine has the potential to change."
Vlasak argues that monkeys are being addicted to PCP, methamphetamine and nicotine.
"It's absolutely correct to say we know tobacco is harmful," Jentsch counters. "It's another thing to say we know why that is, and the why is where the secret of the cure is. It's the most crucial question of all."
Protest tactics are changing. Activists are now taking their fight away from university labs and directly to the homes of researchers. Jentsch's car was fire bombed, he lives with around-the-clock security and faces regular protests and threats.
"I've received razor blades sent to me in the mail with threats to cut my throat," he said.
Dr. Dario Ringach used to experiment on animals at UCLA, but that changed when activists threatened his young children.
"He's no different than those who marched the Jews off to concentration camps," Vlasak said.
Ringach eventually sent an email to the activists with the title "You win." He gave up animal research.
UCLA administrators would not allow Eyewitness News into Jentsch's lab, but he says what life is really like for monkeys in his lab is different than how some may think.
"They live socially, they have enrichment, they've got toys, they live in big exercise cages where they climb around," Jentsch said.
UCLA's animal research website says the way animals are treated is "heavily monitored and subject to stringent and multiple federal laws and university regulations."
The Los Angeles-based Beagle Freedom Project expects to receive 10 to 15 more dogs from a research lab in Colorado next month. Anyone interested in learning more about helping lab beagles can text BEAGLE to 22122.