Florida is facing another struggle with exotic animals set free in the wild. This time, the dangers to people are front and center.

Decades ago, 6 rhesus macaques were released on an island in central Florida’s Silver Spring State Park. The intent was to create an island theme attraction — but no one knew how well the monkeys could swim. The animals fled into the woods on the mainland where their numbers have exploded ever since.

There are now over 300 rhesus macaques in the park — and that’s after hundreds of animals have been removed over the years. Not only can they be aggressive to visitors — they carry herpes B, which is fatal in people. The monkeys also damage mangrove trees and kill native wildlife.

The macaque population is expected to double by 2022. The dilemma is how to manage the population effectively and humanely.