Many animals may respond to the presence of a predator by eliciting a signal that alerts other individuals in the area. Since snakes are a major predator of monkeys, they often respond very strongly whenever one is nearby. The female long-tailed macaque (Macaca fascicularis) in this photo is very upset with a large boa constrictor who is just out of frame on the ground next to her. You can see that she is exhibiting specific anti-predator behaviors such as standing upright in order to better scan the ground nearby, keeping visual contact on the snake and eliciting a specific vocalization that is alerting her group mates of the potential danger.
[Photo and caption by Josie Hubbard]
Coss, R. G., McCowan, B., & Ramakrishnan, U. (2007). Threat‐related acoustical differences in alarm calls by wild bonnet macaques (Macaca radiata) elicited by python and leopard models. Ethology, 113(4), 352-367.
*Authors in bold are UC Davis Animal Behavior Graduate Group faculty!