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blond titi monkey (Callicebus barbarabrownae)

Mohamed bin Zayed Species project number 222529779

The population size of the Critically Endangered blond titi monkey in the Chapada Diamantina National Park, Brazil

Mohamed bin Zayed Species Conservation (Project No. 222529779) - blond titi monkey  - Awarded $12,500 on October 24, 2022

Igor Pfeifer Coelho and André Chein Alonso


The goal of this project was to estimate the abundance of the critically endangered blond titi monkey in the only conservation priority protected area where it is known to exist. Our findings revealed that the Chapada Diamantina National Park is home to the largest population and highest known density of the species.


The blond titi monkey inhabits forests in the Caatinga biome in Northeastern Brazil. Although Caatinga is commonly known as a vast scrubland with dry landscapes and cacti, it wasn't always like this. Caatinga means "white forest" in the indigenous Tupi language, referring to the region's dry forests that were once the main vegetation. Unfortunately, human activities have heavily impacted 63% of the Caatinga, with only 7% being protected areas. Additionally, 94% of the region faces the moderate to high risk of desertification due to land use and climate change.

The blond titi monkey was only discovered 30 years ago and is considered highly threatened with extinction by the IUCN and Brazilian Red Lists. Titi monkeys, specifically the blond titi, are difficult to spot visually as they are shy and cryptic, living in small territorial groups averaging three adults. However, they emit loud calls for intergroup communication and respond to playback calls, which has helped shed light on their distribution and abundance.

In a previous project funded by The Mohamed bin Zayed Species Conservation Fund, playback sampling was used to reveal that the blond titi is more widespread and abundant than previously known. Its occurrence was confirmed in a conservation priority protected area (Alonso et al., 2022). The project also provided the first accurate estimate of the population size, which amounted to 273 adult blond titi monkeys in a 221‐km2 area in Boa Vista do Tupim, Bahia state (Coelho et al., 2020). However, the project also delivered concerning news: forest cover continues to decrease (11% loss from 2005 to 2016), and human occupation is rapidly expanding in the species' range (67% increase from 2005 to 2016; Alonso et al., 2022).

From 2021 to 2023, five main forested areas in the Chapada Diamantina National Park were surveyed using playback calls to count blond titi groups at 212 sampling sites (Figs 1, 2 and 3). N-mixture and occupancy models were utilized to predict group abundance in each area and the species' occurrence in the region. The estimated total population was 873 individuals, with the highest density found in the Chapadinha study area (Table 1). The species was not observed in the Baixão and Pati areas, where the probability of occurrence was less than 12%, as determined by occupancy modeling (Figure 5).

Estimating the number of individuals within protected areas is a crucial goal of the blond titi Conservation Action Plan. Understanding the population size in different areas of the Chapada Diamantina National Park is essential for park management and regional planning to promote connectivity between the remaining Caatinga forests. The results of this project also aim to raise public awareness about the conservation of blond titi monkeys and their habitats – the "white forests" that we much need in their original place.


References and Links

Alonso et al. (2022)

Coelho et al. (2020)

Previous project

Chapada Diamantina National Park

Conservation Action Plan of Primates in Northeastern Brazil



All data, analyses, and accompanying publications are being updated and publicly accessible on the Open Science Framework at https://osf.io/d2cvw/files/osfstorage 

Project documents