Here's why:
* Keystone species have a disproportionately large impact on their ecosystem, often far greater than their abundance would suggest. Their removal can cause dramatic changes in the ecosystem's structure and function.
* Spider monkeys are frugivores, meaning they primarily eat fruit. While they play a role in seed dispersal, their impact on the ecosystem is not as significant as other species like apex predators or ecosystem engineers.
Examples of Keystone Species:
* Wolves: Regulate prey populations, which can impact plant communities.
* Sea otters: Control sea urchin populations, preventing kelp forests from being overgrazed.
* Beavers: Build dams that create habitats for other species and alter water flow patterns.
Spider monkeys are important for their role in seed dispersal and maintaining forest diversity, but their impact isn't as crucial to the ecosystem's stability as that of a keystone species. They are still vital members of their ecosystem and play a role in maintaining its health, but their absence would not cause a drastic collapse of the ecosystem.