Update to the geographical distribution of Sapajus nigritus cucullatus (Spix, 1823) in Southern Brazil

The geographical distribution of Sapajus nigritus cucullatus includes the Brazilian states of São Paulo, Paraná, Santa Catarina, and the northern half of Rio Grande do Sul (RS), and extends into the Misiones province of Argentina. The Camaquã River basin in RS, situated along the 31st parallel, is regarded as the southernmost extent of platyrrhine distribution, including S. n. cucullatus. However, a comprehensive mapping of this taxon occurrence in RS has yet to be conducted. The subspecies inhabits the Atlantic Forest biome. Nevertheless, historical records from points further south in RS, in the Pampa biome, introduce uncertainty regarding the subspecies’ distribution. The objective of this study was to delineate the geographic range of S. n. cucullatus in RS. To this end, we evaluated data from scientific surveys, institutional databases, field observations, and information from citizen science platforms. A total of 146 occurrence records for the subspecies were identified in 82 municipalities, with 37 of these occurrences located within legally protected areas. In addition, we noted that the subspecies co-occurs with Alouatta guariba. This result supports the hypothesis that the subspecies is closely associated with the Atlantic Forest in the RS, yet also occurs in ecotones with Pampas. The absence of this subspecies to the south of the Ijuí and Jacuí rivers and Lake Guaíba was confirmed, corroborating the southern limit suggested in previous studies. The provenance of the isolated population that inhabits the Porto Alegre/Viamão region remains uncertain. This study expands the existing knowledge about the distribution of S. n. cucullatus in RS, confirming subspecies presence or absence in some areas due to environmental factors, and removing incorrect or inaccurate records. Additionally, it identifies the limits imposed on its dispersal by geographical barriers (rivers). Despite the presence of the subspecies in protected areas, it continues to face habitat loss in multiple regions of the state, particularly in the northwest of RS, due to the expansion of agribusiness. It is imperative to safeguard the populations of S. n. cucullatus in legally protected areas and to ensure habitat preservation and restoration in order to maintain the subspecies in RS.