Hunting and Habitat Destruction Drive Widespread Functional Declines of Top Predators in a Global Deforestation Hotspot

Aim: We investigated the effects of habitat destruction and hunting on the functional decline of top predators, specifically jaguar and puma, in the Gran Chaco. Location: The 1.1 million km2 South American Gran Chaco. Methods: We used spatially explicit, individual-based models for jaguars and pumas, incorporating detailed information on habitat suitability and hunting pressure. We parameterized our models with literature data and calibrated them through a Delphi expert-elicitation process. We simulated population trajectories under a hypothetical, threat-free, baseline versus different threat scenarios. Results: Under combined threats of hunting and habitat loss, jaguar and puma populations declined by 88% and 80%, respectively, compared to range contractions of 48% and 35%, respectively. Both species remained regionally viable, particularly due to large protected areas, which acted as population sources but were surrounded by strong sinks. We observed a widespread weakening of the top carnivore guild function, with at least one species extirpated across 67% of the Chaco and strong declines (> 80%; considered here as functional loss) for both species concurrently across 61% of their area of historical co-occurrence. Hunting was a much stronger driver of population declines (88% and 77% for jaguars and pumas, respectively) compared to habitat destruction (26% and 22%). Main Conclusions: Large predators play key functional roles in ecosystems. Our findings reveal that these functions can be lost over vast areas due to the combined effects of habitat destruction and hunting, with functional loss extending far beyond the areas of species' extirpation. Very large protected areas, like Kaa-Iya in Bolivia, are crucial for maintaining viable populations of top predators, highlighting the pressing need for increased protection and connectivity in the Chaco to prevent further trophic downgrading. More generally, our research underscores the value of spatially detailed, mechanistic models for disentangling the complex dynamics of multiple threats on ecological functioning at broad scales.

Instituto de Recursos Biológicos

Fil: Romero Muñoz, Alfredo. Humboldt University. Geography Departament; Alemania.

Fil: Bleyhl, Benjamin. Humboldt University. Geography Departament; Alemania.

Fil: Benitez López, Ana. National Museum of Natural Sciences. Department of Biogeography and Global Change; España

Fil: Camino, Micaela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Ecología Aplicada del Litoral; Argentina

Fil: Camino, Micaela. Proyecto Quimilero, Resistencia; Argentina.

Fil: Decarre, Julieta. Humboldt University. Geography Departament; Alemania.

Fil: Decarre, Julieta. Instituto Nacional de Tecnología Agropecuaria (INTA). Instituto de Recursos Biológicos; Argentina

Fil: Nanni, Ana Sofía. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ecología Regional; Argentina.

Fil: Nanni, Ana Sofía. Universidad Nacional de Tucumán. Instituto de Ecología Regional; Argentina.

Fil: Nanni, Ana Sofía. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Manuel Lillo; Argentina.

Fil: Noss, Andrew J. University of Florida. Department of Geography; Estados Unidos

Fil: Giordano, Anthony. Society for the Preservation of Endangered Carnivores and their International Ecological Study (S.P.E.C.I.E.S); Estados Unidos. UCLA Inst. of the Environment and Sustainability. Center for Tropical Research; Estados Unidos

Fil: Quiroga, Verónica. Universidad Nacional de Córdoba. Inst. de Diversidad y Ecología Animal (IDEA – CONICET) Centro de Zoología Aplicada; Argentina

Fil: Quiroga, Verónica. Consejo Nacional de Investigaciones Científicas y Técnicas. Inst. de Diversidad y Ecología Animal (IDEA – CONICET), Centro de Zoología Aplicada; Argentina

Fil: Quiroga, Verónica. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas, Físicas y Naturales. Centro de Zoología Aplicada; Argentina

Fil: Torres, Ricardo. Universidad Nacional de Córdoba. Inst. de Diversidad y Ecología Animal (IDEA – CONICET). Centro de Zoología Aplicada; Argentina

Fil: Torres, Ricardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Inst. de Diversidad y Ecología Animal (IDEA – CONICET). Centro de Zoología Aplicada; Argentin

Fil: Torres, Ricardo. Universidad Nacional de Córdoba. Museo de Zoología; Argentina

Fil: Thompson, Jeffrey J. Guyra Paraguay-CONACYT; Paraguay

Fil: Thompson, Jeffrey J. Instituto Saite, Asunción; Paraguay

Fil: Villalba, Laura. Wildlife Conservation Society; Paraguay

Fil: Nuñez Regueiro, Mauricio M. The Nature Conservancy; Argentina

Fil: Nuñez Regueiro, Mauricio M. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Bio y Geociencias del NOA; Argentina

Fil: Nuñez Regueiro, Mauricio M. Universidad Nacional de Salta. Instituto de Bio y Geociencias del NOA; Argentina

Fil: De Angelo, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina

Fil: De Angelo, Carlos. Universidad Nacional de Río Cuarto. Instituto de Ciencias de la Tierra, Biodiversidad y Ambiente; Argentina

Fil: Kuemmerle, Tobias. Humboldt-University. Geography Department; Alemania.

Fil: Kuemmerle, Tobias. Transformations of Human-Environment Systems (IRI THESys). Integrative Research Institute; Alemania