Looking for a needle in a haystack: Testing new methods for surveying an endangered population of brown howler monkeys

AGOSTINI., I; HOLZMANN, I; VARELA D., ; DE ANGELO., C; PIZZIO E., ; CRUZ., P; PAVIOLO A., ; DI BITETTI M

Foz do Iguacu

Simposio; 3rd International symposium of Ecology; 2018

The brown howler monkey (Alouatta guariba clamitans) is on the verge of extinction in Argentina, due to yellow fever epidemics and habitat loss. Since the last yellow fever outbreak that decimated howlers in 2008, the brown howler is at risk of disappearing due to suspected extremely low numbers that survive along the east of Misiones province (NE Argentina). Since Misiones hosts one of the largest remnants of Atlantic Forest, maintaining a healthy population of brown howlers in this area is important for the species long-term viability at the global level. One priority is implementing a monitoring program to keep track of the areas occupied by the species. However, surveying this rare and elusive species using traditional transect census surveys has become unfeasible. Thus, we propose evaluating the efficiency of a novel technique, such as automated sound recording devices, with validated methods such as camera trapping and local participatory monitoring networks. We selected two provincial parks where brown howlers were recently confirmed, Piñalito (26°30´S, 53°50´W; 3796 ha) and Cruce Caballero (26°28´S, 53°58´W; 600 ha). Between June and August 2018, we set 20 survey stations (500 m apart) equipped with a Song Meter SM4 automated acoustic recorder in Piñalito. A subset of eleven stations was also equipped with two Reconyx HC500 camera traps pointing to branches potentially used by monkeys. This design will be replicated in Cruce Caballero in 2019. In parallel, we are starting a participatory monitoring program, using an application (Epicollect5), that allows data collected by multiple field workers to be submitted by smartphone, together with GPS data, to a common web database and be analyzed using Google Earth. Our results will help develop effective monitoring protocols for brown howlers, providing data on population trend, as well as a tool for early detection of yellow fever outbreaks.