Mustached Monkeys' Feces Helped Regenerate Amazonian Rainforest Destroyed by Humans, Scientists Say

The feces of mustachioed monkeys helped regenerate parts of the Amazonian rainforest destroyed by humans, scientists believe.

An international team of scientists studied an area spanning around four hectares (47,000 square yards) in the Amazonian rainforest of north-eastern Peru, which was cleared to graze water buffaloes for almost a decade following 1990. Farmers left the land in 2000, and the rainforest gradually began to regrow.

Scientists based at the nearby Estación Biológica Quebrada Blanco (EBQB) research station noticed there were mustached and black-fronted tamarins in the new forest. As the primates eat fruit and pass out the seeds in their feces, the team out to understand whether monkeys helped the rainforest to regrow. Their findings were published in the journal Scientific Reports.

primate, black-fronted tamarin, monkey,
An image of a black-fronted tamarin (Leontocebus nigrifrons) captured by the researchers in the rainforest of Peru. German Primate Center, Germany

More and more parts of tropical forests are being demolished to make way for human activity, from the construction of hydroelectric dams and roads to farming, according to the researchers.

Sometimes these woody areas can't repopulate naturally. If they can, plant seeds must somehow be spread: and animals play an important part in this. First, animals such as bats and birds might defecate as they fly over an area, leaving behind seeds. As plants grow, they attract animals such as primates.

Over a period of 20 years, the researchers studied how these two species of monkey interacted with the repopulating pasture. As more plants emerged, the team found the monkeys used the deforested area increasingly, bringing with them seeds from the existing rainforest. They also studied the seedlings from the re-emerging forest and compared them to the plants in the existing forest. The team noted that different plants of the same species had varying heights, suggesting the seeds from which they emerged were brought to the area in different years.
Eckhard W. Heymann, scientist at the German Primate Center and head of the study, commented in a statement: "Our data show for the first time that the mustached and black-fronted tamarins effectively disperse seeds from the primary forest into secondary forest."

"We were able to prove that the seeds germinate and form young plants, thus increasing the diversity of species in the secondary forest. The tamarins have been shown to contribute to the natural regeneration of areas destroyed by humans."

"We did not expect the cleared forest area to ever recover," said Heymann.

"However, the study shows how important data collection and investigations over a very long period of time are in order to be able to make reliable statements about slowly developing ecological processes," he said.

T. Mitchell Aide of the University of Puerto Rico, who has studied deforestation but did not work on this paper, told Newsweek it highlights the importance of long-term monitoring in forests. "If the researchers had not been returning to the same site for more than 20 years these dynamics would not have been documented."

He continued: "Young secondary forests can provide habitat for many forest species, but only if they persist. The authors show that there are food resources for the monkeys in these young forests, but even after 20 years of recovery they still do not have the structure for the monkeys to use for sleeping.

"Twenty years is a long time, but to provide the structure and species composition that the fauna needs, these forests have to persist for much longer: more than 40 to 50 years, and hopefully longer."

This article has been updated with comment from T. Mitchell Aide.