Brown howler monkeys (Alouatta guariba clamitans)

Mohamed bin Zayed Species project number 10251570

 

Brown howlers (Alouatta guariba) are one of the endemic primate species of the Atlantic Forest, ranging from the Brazilian states of Bahia and Espirito Santo in the North to Rio Grande do Sul and the Argentine Province of Misiones in the South. Brown howlers have been recently re-classified globally from Near Threatened to Least Concern by the IUCN due to the presence of the species in most of the extant conservation units of the Atlantic Forest in Brazil. However, the population trend is "decreasing" and the future of this species is quite uncertain, since Brazilian Atlantic Forest is dramatically reduced and fragmented, thus probably affecting survival probability for the specie in the long term. In Argentina, the brown howler (Alouatta guariba ssp. clamitans) has been classified
as "endangered" and included in the national list of the most threatened mammals species compiled by the Argentine Society for the Study of Mammals (SAREM) and by the National Authority in Fauna and Flora of Argentina. The province of Misiones has declared this species by law a Provincial Natural Monument. Although the brown howler population in Argentina is suspected to be on the verge of extinction, no thorough assessment of the population and conservation status of this species has been conducted up to now for this area. Between 2005 and2007, together with Dr. Mario Di Bitetti and Ingrid Holzmann, I carried out a comparative study on the behavioral ecology of brown howlers living in sympatry with the congeneric black and gold howler monkeys
(Alouatta caraya) in one protected area of Misiones, El Piñalito Provincial Park. Then, in 2008 and 2009 yellow fever outbreaks killed all our study groups and dramatically decimated howlers throughout Argentina. Due to the suspected high impact of this epidemics, there is a special concern about the current status of the brown howler, which is the rarest howler species in Argentina, only restricted to Eastern Misiones. Given its initial small size, the remnant brown howler population is now considered to be seriously endangered, and at risk of disappearing from Misiones in the next few decades due to the increasing habitat loss and new yellow fever outbreaks. In order to develop an effective conservation strategy, an assessment of the current population status and the main threats affecting the brown howler in the region has become critical. With the objective of filling this knowledge gap, we designed a study to examine the occupancy patterns of brown howlers and evaluate the factors affecting the species presence throughout its distribution in Argentina. Occupancy pattern of a species across different sites of its distribution is one of the most useful measures to evaluate the population status of a species and constitute a necessary and basic information for the development of a population viability analysis. During the survey period, we realized census transects, as well as semi-structured interviews with local people about the presence/absence of howlers. Overall, results indicate that both howler species currently present a very scattered distribution and have been severely decimated by the recent yellow fever epidemics. On the basis of these alarming results, we started a monitoring program focused at recording the presence of both howler species in locations where they are known to be present as well as in new locations, involving park rangers. Further, we are working at the organization of the first "Brown Howler Monkey Conservation Workshop: Population Viability Assessment (PVA)" that will be held in Puerto Iguazú, Misiones, Argentina, in 2012, with the purpose of evaluating the current brown howler population status, the main threats, and the potential management alternatives that are most likely to be effective with the objective of preserving the species.