How the Howler Monkey Keeps His Tree

08-27-2019

By Monica Leal, local Expedition Guide on the Safari Voyager

It was a beautiful morning in Curu Wildlife Refuge in Costa Rica. Everybody got in the skiff, excited to see a new ecosystem and the tropical dry forest of Curu. As soon as we approached with our skiff, the sound of the engine let the resident howler monkeys know about our presence and they started howling. 

The males were howling so loud that our travelers thought dogs were barking. Getting a better view, we discovered that it was only two males lazily hanging in the branches, barely moving while they ate. Their unique vocalizations make it possible to hear them about two and a half miles away. They are the wakeup call of the tropical forest.

The howler monkey has a hollow bone near the vocal cords that is 25 times larger than any other in the tropical forest. When they are howling, their sounds amplify like chambers of resonance. They are the only vegetarian monkey we have in Costa Rica, allowing them to remain more stationary, compared to the white-faced monkey or spider monkey. They can spend almost all day in the same tree, sleeping, eating, and howling.

Our guests spent almost twenty minutes watching the monkeys and taking pictures of them. One of the moments that caught our attention was when a male howler monkey approached a wasp nest and hit the nest - just to scare the white-faced monkeys that were arriving there to eat from the same tree as the howlers. The startled white-faced monkeys ran away to another tree, allowing the howler monkeys to stay in the tree they wanted.

It was a special moment for everybody to see this territorial behavior, and it was a good moment as a guide to learn.

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