In most labs, daily life is punctuated by intense fear. For chimpanzees, this fear is often connected with a procedure called a 'knockdown.'
Because chimpanzees are several times stronger than humans, most must be anesthetized for even minor procedures such as drawing blood or injections. A 'knockdown' typically involves one or more workers approaching the chimpanzee through the bars with a dart gun loaded with anesthetic. It often requires several darts to 'down' a chimpanzee as he/she screams and thrashes around in a futile attempt to avoid being shot. Darts have been known to hit them in the face or other sensitive areas. It is so terrifying they typically lose control of their bladder and bowels.
According to Nancy Megna, a former caregiver at both the Yerkes National Primate Research Center in Atlanta and the Laboratory for Experimental Medicine and Surgery in Primates (LEMSIP—now closed), “They NEVER EVER get used to it.” In her experience, out of resignation some chimpanzees have been known to offer their arms out of resignation to be anesthetized with a needle to avoid being darted.
Former caregivers explain that chimpanzees know when a knockdown is about to occur because their food and water is withheld—leaving them in anxious anticipation. Many chimpanzees have endured several hundred knockdowns in their years of research (read about Billy Jo and Pepper).