When Ever I Watch A Program About Baboons And Gorillas,

amongst other primates,

the program presenter always mentions that looking at one of them straight in their eyes can be interpreted as a sign of aggression and the prelude to a fight, which is what happened at Rotterdam Zoo a few years ago, so here is the answer, a pair of glasses that makes it look like you are looking away, but can in fact look straight at the creature you are studying, the glasses are loaned to visitors to the zoo, now here is a tip, remember not to wear them when you leave the zoo.