Fear reactions to snakes in naïve mouse lemurs and pig-tailed macaques.

Primates have been predated on by snakes throughout their evolution and as a result, antipredator responses accompanied by signs of fear are often witnessed in the wild. In captivity, however, the fear of snakes is less clear, as experiments with naïve nonhuman primates have given inconsistent results. In this study, we present evidence that naïve mouse lemurs (Microcebus murinus) and putatively naïve pig-tailed macaques (Macaca nemestrina) do exhibit fear of snakes, even though the apparent reactions are mild. In an experiment with control- or snake-odoured boxes, mouse lemurs clearly avoided feeding in the latter. When the latency of touching rubber models was measured, pig-tailed macaques took longer to touch a toy snake compared with a toy lizard. Our findings that fear of snakes is shown by naïve individuals support the hypothesis that it is innate in primates.