“When I was a child living on the southern Pacific coast of Costa Rica, my parents would take me to see golden-mantled howler monkeys (Alouatta palliata palliata) in the forest most weekends. Howler monkeys are like big, hairy gardeners, spreading seeds from many trees. I understood at an early age that if we preserve the forest, we preserve the species in it.

For the past decade, I’ve studied the behaviour of howler-monkey troops in Guanacaste, a region in northern Costa Rica where tourism is growing rapidly and hundreds of monkeys die from electrocution each year. For my master’s degree at the University of Costa Rica, I evaluated how monkeys use modern structures such as power lines to navigate through an urban area. I ended up taking a lot of electrocuted monkeys to rescue centres. We are documenting how this species’ behaviour is changing in real time.

We track where troops move and what they’re eating, and note the percentage of forest cover in each location. Although we don’t know whether the overall number of monkeys is declining, we do know that troops located in healthy protected forests, for example in a national park, have roughly 25–45 individuals, compared with an average of only 7 in urban troops.