Ranging from North America to Argentina and categorized as Near Threatened on the IUCN Red List (Quigley et al., Reference Quigley, Foster, Petracca, Payan, Salom and Harmsen2017), most jaguar Panthera onca populations are declining because of habitat loss, prey depletion, retaliatory killings and the illegal trade of body parts (de la Torre et al., Reference de la Torre, González-Maya, Zarza, Ceballos and Medellín2017; Nuñez & Aliaga-Rossel, Reference Nuñez and Aliaga-Rossel2017; IUCN Netherlands, 2020; Arias et al., Reference Arias, Hinsley, Nogales-Ascarrunz, Negroes, Glikman and Milner-Gulland2021). Habitat loss at the extremes of the jaguar's range tends to increase isolation, dividing populations into smaller and more threatened subpopulations (de la Torre et al., Reference de la Torre, González-Maya, Zarza, Ceballos and Medellín2017; Thompson et al., Reference Thompson, Velilla, Morato, De Angelo, Paviolo and Quiroga2021). In Argentina jaguars are categorized as Critically Endangered (Paviolo et al., Reference Paviolo, De Angelo, De Bustos, Perovic, Quiroga and Lodeiro Ocampo2019), with a 95% reduction of their historical distribution (Di Bitetti et al., Reference Di Bitetti, De Angelo, Quiroga, Altrichter, Paviolo, Cuyckens, Medellín, de la Torre, Zerda, Chávez and Ceballos2016), whereas in Bolivia they are categorized as Vulnerable, with a 50% reduction of their historical distribution (Aguirre et al., Reference Aguirre, Tarifa, Wallace, Bernal, Siles, Aliaga-Rossel and Salazar-Bravo2019).

The mountain forests that make up the Austral Yungas ecoregion extend on both sides of the Argentina–Bolivia border, occupying an area of c. 56,000 km² (Malizia et al., Reference Malizia, Pacheco, Blundo and Brown2012) and hosting the southernmost jaguar population of the Yungas (Perovic et al., Reference Perovic, De Bustos, Rivera, Arguedas Mora and Lizárraga2015), one of the two southernmost jaguar enclaves (Di Bitetti et al., Reference Di Bitetti, De Angelo, Quiroga, Altrichter, Paviolo, Cuyckens, Medellín, de la Torre, Zerda, Chávez and Ceballos2016). This is a diverse region, with an altitude range of 400–2,300 m, and high beta diversity and endemism (Brown et al., Reference Brown, Grau, Malizia, Grau, Kapelle and Brown2001). However, the Yungas face major threats: large-scale deforestation has occurred across all altitudes (Politi et al., Reference Politi, Hunter and Rivera2012). In Argentina, 31% of this forest had been cleared by 2010 (Malizia et al., Reference Malizia, Pacheco, Blundo and Brown2012) and 35% by 2021 (Global Forest Watch, 2022); in Bolivia, 32% of this forest had been lost by 2021 (Global Forest Watch, 2022). The loss of native forests is a result of large-scale agriculture, extensive livestock farming, timber extraction, infrastructure development, exploration for fossil fuels, and forest fires (Perovic et al., Reference Perovic, De Bustos, Rivera, Arguedas Mora and Lizárraga2015; MMAyA, 2020; Thompson et al., Reference Thompson, Velilla, Morato, De Angelo, Paviolo and Quiroga2021). Fires are often initiated by local people, ranchers, farmers and sugar refineries to clear land for crops, to supposedly improve pastures and to justify logging (Perovic et al., Reference Perovic, De Bustos, Rivera, Arguedas Mora and Lizárraga2015; MMAyA, 2020). Fires cause drastic changes in forest cover, structure and species composition, and may be accompanied by mortality, or displacement of species, changing the supply of resources and the quality of habitat for jaguars and their native prey (Perovic et al., Reference Perovic, De Bustos, Rivera, Arguedas Mora and Lizárraga2015). These multiple and largely uncontrolled threats could lead to the loss of connectivity between the remaining Yungas between Argentina and Bolivia (Perovic et al., Reference Perovic, De Bustos, Rivera, Arguedas Mora and Lizárraga2015; Maffei et al., Reference Maffei, Rumiz, Arispe, Cuéllar, Noss, Medellín, de la Torre, Zerda, Chávez and Ceballos2016; Quigley et al., Reference Quigley, Foster, Petracca, Payan, Salom and Harmsen2017).

In 2005 a binational initiative proposed the creation of a 4,212 km² Baritú–Tariquía Biological Corridor linking the best-preserved sectors of the Argentine–Bolivian Yungas (PROMETA, 2005) and connecting two protected areas where jaguars are known to be present: Tariquía National Reserve (2,469 km², Bolivia) and Baritú National Park (724 km², Argentina). This initiative aims to maintain cross-border connectivity and facilitate the movement of animals between the two protected areas (Cuyckens et al., Reference Cuyckens, Falke and Petracca2014; Perovic et al., Reference Perovic, De Bustos, Rivera, Arguedas Mora and Lizárraga2015; Maffei et al., Reference Maffei, Rumiz, Arispe, Cuéllar, Noss, Medellín, de la Torre, Zerda, Chávez and Ceballos2016). However, the Baritú–Tariquía Biological Corridor is still awaiting effective legal protection, despite it being essential for ensuring the connectivity of the jaguar population straddling the border.

Local residents have reported jaguar sightings along the Baritú–Tariquía Biological Corridor (Cuyckens et al., Reference Cuyckens, Falke and Petracca2014), prompting us to carry out a camera-trap survey. During June 2019–March 2020, we surveyed an area of 1,243 km² across the Corridor to confirm jaguar presence (Fig. 1). We used 50 stations, each with a single camera (Trophy Cam HD, Bushnell, Overland Park, USA), placed c. 5 km apart. We placed the cameras along trails, streams and mountain ridges. This resulted in a camera-trapping effort of 10,695 trap-days.

Fig. 1 Baritú–Tariquía Biological Corridor joining Baritú National Park (Argentina) and Tariquía National Reserve (Bolivia), indicating the locations of camera traps and cameras with jaguar records (the latter are numbered).

We recorded jaguars at six sites across the Corridor, and identified at least three individuals. In Bolivia during September–December 2019, jaguars were recorded at five sites, all between Tariquía National Reserve and Baritú National Park: a mountain ridge in Cayotal village (Fig. 1, site 40); a site 1.5 km from Angosto de Alarachi, suggested as a potential jaguar border-crossing point (Cuyckens et al., Reference Cuyckens, Falke and Petracca2014; Fig. 1, site 42; Plate 1a); 1.8 and 2.0 km from Tariquía National Reserve (Fig. 1, sites 78 and 76, respectively); and near Campo Grande village c. 3 km from Bermejo River (Fig. 1, site 10). In Argentina three jaguars were photographed during March–April 2020: two by the same camera but 49 days apart, 1.45 km from Bermejo River and 5.00 km from Baritú National Park (Fig. 1, site 74; Plate 1b); and a third individual photographed in April 2020, 800 m from Bermejo River (Fig. 1, site 58).

Plate 1 (a) Adult male jaguar Panthera onca recorded by camera trap 42 on a mountain ridge in Sidras village (Bolivia). (b) Adult jaguar recorded by camera trap 74, 1.45 km from Bermejo River and 5.00 km from Baritú National Park (Argentina).

From our survey we conclude that jaguars are present in the Baritú–Tariquía Biological Corridor, and that their occurrence at several sites and the presence of several individuals suggest that this is a functional corridor for this key jaguar population. The records reinforce the designation of this area as a Jaguar Conservation Unit (Baritú-Calilegua Jaguar Conservation Unit) and support the proposal to connect it with jaguar populations in the Chaco and Gran Chaco (Thompson et al., Reference Thompson, Velilla, Morato, De Angelo, Paviolo and Quiroga2021). Confirmation of jaguars in this area between Argentina and Bolivia provides a strong argument for securing legal protection for the Corridor and for involving the local community in updating its management plan and demarcating strategic areas for the sustainable management interventions required to restore and maintain connectivity.

International borders are generally drawn for political rather than ecological reasons and consequently conservation targets on either side of a border are potentially subject to different laws and environmental management practices. Transboundary conservation is of paramount importance for jaguars and habitat connectivity but presents important challenges as cross-border collaborations can be complex, costly and time-consuming. Proposed priority sites and actions resulting from this research are being discussed by a number of institutions, including the Administracion de Parques Nacionales of Argentina, the provincial governments of Salta and Jujuy, the Servicio Nacional de Areas Protegidas of Bolivia, the departmental government of Tarija-Bolivia, NGOs and local people.

The implementation of cross-border conservation projects in the Baritú–Tariquía Biological Corridor can deliver multiple benefits. However, to achieve this, a set of conditions must be met, including achieving effective protected area management, recruiting, training and equipping rangers, and improving funding for monitoring and field research.