Largest primate in the Americas is key to reforestation in São Paulo heartland

At the Barreiro Rico Ecological Station in Anhembi, different approaches are shared between researchers in an effort to understand the relationship between the forest and the Southern muriqui, and to connect populations by means of ecological corridors. Fire prevention in the area has allowed the group to thrive after almost disappearing.

By André Julião in Anhembi  |  Agência FAPESP* – Surrounded by pasturelands, sugarcane plantations, eucalyptus stands and orange groves, a 292-hectare conservation unit deep inside São Paulo state (Brazil) is home to five of around 1,300 Southern muriquis (Brachyteles arachnoides) remaining in the wild. This species and the Northern muriqui (B. hypoxanthus) are endemic to the Atlantic Rainforest on the coast of Brazil and are the largest primates in the Americas.

Observation of the family that lives in the Barreiro Rico Ecological Station, a state conservation unit created in 2006, is not easy for humans: we humans lost the ability to swing through the forest long ago and must try to spot the muriquis from the ground as they forage high up in the trees.

One morning in August, Beatriz Robbi, a PhD candidate affiliated with the Wildlife Management and Conservation Laboratory at the Federal University of Viçosa (UFV), flew a drone with a thermal sensor and camera over the treetops.

In the early morning and late afternoon, when the temperature is lower and branches and leaves are cooler, the muriquis are most likely to be detected from the heat emitted by their bodies.

With four batteries, each lasting 20 minutes, the drone covers much of the area. When the researchers detect muriquis, whether singly or in groups, they observe the animals’ behavior to see what they are eating, whether they are mating, and whether the females are pregnant or are carrying infants, among other things. Data collection proceeds until sunset, when the animals are moving to prepare for sleep. No muriquis were detected when Agência FAPESP was there on August 21-22, 2024.

“Altogether there are 12 known individuals in the Barreiro Rico Environmental Protection Area, which with the Ecological Station comprises a mosaic of some 30,000 hectares, with farms, businesses and fragments of Atlantic Rainforest. Between these fragments there are roads, high-voltage power lines, plantations, pasturelands and buildings, making it hard or impossible for groups of these animals to meet and mate,” Robbi said.

Connecting the population of muriquis is essential to conservation of the species, which will also help protect the four other primate species that live in the area – the Brown howler (Alouatta guariba), Robust capuchin monkey (Sapajus spp), Buffy-tufted marmoset (Callithrix aurita) and Atlantic titi monkey (Callicebus personatus) – as well as the more than 200 bird species and over 30 terrestrial mammals, such as coatis, ocelots, cougars, anteaters and peccaries.

To connect Atlantic Rainforest fragments, a group of researchers, non-governmental organizations (NGOs) and Fundação Florestal, which manages conservation units in São Paulo state, are establishing what they call ecological corridors. These are strips of vegetation, underpasses or overpasses that provide a safe passage for animals without human intrusion.

Restoration

According to Luana Carvalho, a master’s candidate affiliated with the Tropical Silviculture Laboratory (Lastrop) at the University of São Paulo’s Luiz de Queiroz College of Agriculture (ESALQ-USP) who is also doing research in the area, the forest fragments with the most ecological value for the muriquis – those that still have sufficient quality for their reproduction, foraging and shelter – can be identified by studying the ecology of the landscape and also by remote sensing.

“On that basis, we’ll be able to determine where and how to connect the fragments. We’re prioritizing tree species used by the muriquis for foraging and shelter, and this will enable us to guide forest restoration focusing on the species. We’ll be able to create ecological corridors that will expand forest cover and provide the necessary foraging resources while respecting the needs of each tree species,” Carvalho said.

Researchers are collecting data on the plants most used by the Southern muriqui in the Anhembi area. The data can guide reforestation to connect Atlantic Rainforest fragments (photo: Beatriz Robbi/UFV)

Her project, supervised by Edson Vidal, one of the coordinators of Lastrop and a professor at ESALQ-USP, aims to understand the structure of the forest and how it supports wildlife. The area studied is part of a 4% semi-deciduous seasonal forest remnant in the Atlantic Rainforest biome. Drier than ombrophilous rainforests, such as Serra do Mar (literally meaning “sea ridge” in Portuguese), for example, semi-deciduous forest loses part of its leaves during the dry season to enable the trees to conserve water.

The restoration planned for the area is part of an initiative funded by Petrobras that is establishing ecological corridors to connect forest fragments.

“The project aims to connect forest fragments so that they’re no longer isolated and biodiversity can thrive. Isolation greatly increases the risk of extinction for species with declining populations. The animals need connection to reproduce and forage, and even to improve their chances of not disappearing due to some uncontrolled event such as wildfires that often destroy areas like this, for example,” said Pedro Brancalion, a professor at ESALQ-USP and co-coordinator of Lastrop.

Brancalion leads the Thematic Project “Understanding restored forests for benefiting people and nature – NewFor”, supported by FAPESP under the aegis of its Research Program on Biodiversity Characterization, Conservation, Restoration and Sustainable Use (BIOTA), and by the Netherlands Organization for Scientific Research (NWO).

Barreiro Rico recently joined the 50-odd areas studied by NewFor, which selects forest plots of 900 sq. m. each and monitors all trees with a diameter at breast height (DBH) of more than 5 cm. NewFor has so far studied some 800 plots in almost the entire Atlantic Rainforest biome.

Every month Robbi visits the plots monitored by NewFor in Barreiro Rico, counting flowers, fruits and seeds to check the food supply for the muriquis that live in the forest. In parallel, she and Carvalho collect the muriquis’ droppings to find out which fruits they consume and increase the number of plant species indicated for the area.

“The muriquis are considered gardeners of the forest. They’re important to the maintenance of the Atlantic Rainforest. They eat fruits with large seeds and are the main dispersers of tree species such as cambuí [Myrciaria cuspidata], jatobá [Hymenaea courbaril] and copaíba [Copaifera langsdorffii], which other animals are unable to disperse,” Carvalho said.

Some of these seeds only germinate after they pass through the animal’s digestive tract, which breaks dormancy. Local extinction of the primate even in small fragments like Barreiro Rico Ecological Station would therefore cause a significant degradation of the forest due to loss of plant species.

Fire

The number of muriquis who have lived in Barreiro Rico in the not-very-distant past is estimated at between 200 and 500. The group that inhabited the ecological station was even smaller in 2018 when the last wildfire to ravage the area occurred. They recovered, however, and two babies were born in 2023 and 2024.

There have been no more fires in recent years, but this is no miracle, given the rise in temperatures and ever-longer dry seasons. According to João Marcelo Elias, manager of the ecological station for Fundação Florestal, many factors have contributed to the absence of fires like one in 2012, which destroyed an area of 750 ha, some of it inside the ecological station.

“The state government invested in human resources, vehicles with 500 liters of water, personal protective equipment, swatters, hoses, backpacks, and training of volunteer firefighters. This is essential to prevent an ignition point from becoming a raging wildfire like what we’re seeing now,” Elias said, referring to the 110,000 wildfires recorded across Brazil in 2024.

Besides investment by the state government via SP Sem Fogo (“São Paulo Without Fire”), a project of the Department for the Environment, Infrastructure and Logistics (SEMIL), Elias attributed this success to engagement with landowners, businesses and the general public in the vicinity. In addition to the 500-liter water trucks, the ecological station now has reserves of 7,000 liters, and nearby properties have thousands more. And there have been vigorous educational campaigns to make everyone aware that they should not light bonfires, clear vegetation by burning, throw away lighted cigarettes, or even let a hot tractor engine touch a bundle of sugarcane straw, especially in the dry season (usually April-September in this part of Brazil).

“People have a stronger sense of belonging to the area, and the muriqui is our best poster child,” Elias said.

*Daniel Antônio and Phelipe Janning collaborated.