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Belize’s Cockscomb Basin’s Howler Monkey Translocation Is Declared a Success

A howler monkey feeds on the leaves of a trumpet tree over the entrance to the Cockscomb wildlife sanctuary. Photo credit: Scott Silver/WCS.

By Scott Silver and Linde Ostro

For 30 days in April and May, 2017, a team of researchers surveyed the Cockscomb Basin Wildlife Sanctuary and its surrounding environs for Central American black howler monkeys (Alouatta pigra). The Cockscomb monkeys are descended from animals that were first brought into the sanctuary 25 years ago in an effort to reintroduce howler monkeys to the area.

Howler monkeys had disappeared from the Cockscomb in the late 1970’s due to a combination of factors, including: Hurricane Hattie in 1961, which leveled as much as 90 percent of the canopy in the basin; a yellow fever epidemic; and uncontrolled hunting before the area was protected.

Nice view of the east basin of the Cockscomb Basin – now home to an entirely new howler monkey population. Photo credit: Margaret Snyder.

Between 1992 and 1994 the Wildlife Conservation Society, the Belize Audubon Society, and Community Conservation Consultants Inc. translocated 62 monkeys in 14 social groups from the Community Baboon Sanctuary in northern Belize to the Cockscomb Basin Wildlife Sanctuary, a 400-square-kilometer protected area 100 km to the south.

The basin was first declared a protected area in 1984, but the high mountain ridges surrounding the basin and human activity at the entrance prevented howler monkeys from re-colonizing the area on their own. The monkeys were studied intensively from 1992 through 1995 and surveyed regularly until 2007.

A howler monkey male peers out of a Bri-bri tree. Photo credit: Rachel Gibbons.

Twenty-five years on, we are pleased to report that the reintroduction is a success. The howler monkeys have re-established themselves throughout the Cockscomb Basin, and are even found in villages and forested areas bordering the sanctuary. The team found 67 howler monkeys and evidence of many more.

Once again, the deep throated-roar of howler monkeys is a regular sound that echoes through the forests of the Cockscomb Basin, and howling battles can be heard bouncing back and forth over the forest canopy as male howler monkeys announce their presence to neighboring troops.

Howler monkey habitat in the Cockscomb Basin Wildlife Sanctuary. Photo credit: Scott Silver/WCS.

Considering we were only able to intensively survey less than a third of the sanctuary, it is likely that the Cockscomb is now home to several hundred monkeys. In addition to the 67 monkeys observed, many other groups were either heard howling or left sign of inhabiting areas up to 20 kilometers away from the original release sites. During the month-long survey effort, we found howler monkeys living in nearly all the suitable areas we surveyed throughout the Cockscomb.

The opportunity to re-introduce an entire population of monkeys into an area conducive to their survival but where a resident population is absent is rare. We are doubly fortunate to have had the opportunity to study this population in the intervening years. The Cockscomb howlers appear to have done very well, and we believe the translocation and reintroduction effort has been a great success.

An adult female howler monkey peers down at researchers in the Cockscomb. Photo credit: Margaret Snyder.

That success extends far beyond the monkeys themselves. The presence of howler monkeys in the Cockscomb Basin also benefits the rest of the wildlife and the plant communities that are found there. As seed dispersers, howler monkeys play a critical role in helping the species of fruits they consume to survive and thrive.

This means that for the last 25 years, the tree composition in the Cockscomb has likely begun to slowly return to the mix of tree species that was there for thousands of years when howler monkeys were present in the Cockscomb Basin. This in turn probably benefits many other species that evolved strategies for survival in a forest that grows up with howler monkeys as part of the ecosystem.

Some of the researchers who surveyed the Cockscomb for the howler monkeys. From left to right: Delwin Guevara, Scott Silver, Maggie Snyder, Brijilio Bolon, and Angel Pop. Photo credit: Margaret Snyder.

The howler monkeys also provide visitors with a wonderful wildlife-viewing opportunity. While Cockscomb is famous as the world’s first jaguar reserve, and has an abundance of jaguars, they are rarely seen by the casual visitor. By contrast, howler monkeys are slow moving, active during the day, and regularly seen by visitors. And being howlers, they are even more often heard.

Seeing cars pulled over alongside the Cockscomb road as tourists get out to watch monkeys in the trees above is a testament to how much they enhance a visitor’s experience to the park. The roars of howler monkeys echoing off the hills and trees is a moving and much appreciated part of any visit to the area. But it’s also a stirring reminder of the power of conservation to restore and sustain a complex ecosystem.

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WCS biologist Dr. Scott Silver and his wife Dr. Linde Ostro led the recent survey and were part of the original translocation project in the 1990s. They were ably assisted by several volunteer field assistants and the Belize Audubon Society wardens of the Cockscomb Basin.

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[The writers wish to thank the Coypu Foundation, which funded the original translocation, the survey in 2007, and this recent survey.]