On the occurrence of the Critically Endangered blond titi (Callicebus barbarabrownae): reassessment of occupied areas and minimum population size.

Despite their importance to conservation strategies, baseline data on species distribution and abundance are lacking for many primates. Discovered 30 years ago, the blond titi (Callicebus barbarabrownae) is considered Critically Endangered. The first assessments in 2004-2006 sampled 126, 1-km radius areas using interviews, sightings, and playing back loud calls to confirm the presence of this species in 37 areas, suggesting a minimum population of 260 individuals in the Caatinga biome, Brazil. Ten years later, from 2015 to 2017, we reassessed the species' distribution range using playback points to survey 224, 1-km radius areas, including 34 occurrence areas from 2004-2006. We counted the number of responding or sighted groups and individuals in each area. We also measured land cover change from 2005 to 2016 in the species' geographic range. We recorded blond titis in 92 areas, including 28 of the 34 areas occupied in 2004-2006, and three protected areas. We found 194 groups and at least 404 individuals. From 2005 to 2016, forest cover decreased by 11% and urban area increased by 67%. The higher number of occupied areas and individuals we found in 2015-2017 are likely due to the higher sampling effort employed and higher detectability of playback surveys compared to interviews. Although the blond titi occurs in more areas and in higher numbers than previously known, threats related to land use are increasing. We suggest the use of improved observational (e.g., playback) and analytical methods to enhance knowledge of primate distribution and population size. [ABSTRACT FROM AUTHOR]