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Mammal defaunation negatively affects the regeneration of the critically endangered Araucaria angustifolia

Published Article

Brazil

Publication date: July 8, 2026

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This study examines how mammal defaunation and small mammal communities affect regeneration of the critically endangered Araucaria angustifolia in southern Brazil. Results show that loss of medium and large mammals reduces forest regeneration, highlighting the importance of wildlife conservation for maintaining Araucaria Mixed Forest ecosystems.

Subject Tags

  • Forests
  • Biodiversity

Abstract

Overexploitation of forest systems by human actions can lead to the local and selective extinction of animal species, a phenomenon known as defaunation. Several studies showed increased abundance of small mammals under high-defaunation of medium- and large-bodied animals. The absence of seed dispersers can preclude the regeneration of several plant species. Araucaria angustifolia is classified as a keystone and a critically endangered species, so understanding the factors limiting its regeneration is essential. The main objective of this study was to quantify the effects of small mammal richness and mammal defaunation under the regeneration of araucaria across a regional scale in southern Brazil. We expected that sites with greater defaunation and larger assemblages of small mammals would demonstrate less regeneration – since this could lead to reduced seed dispersal and increased seed predation. Our best-fitting model considered adult density, defaunation, richness of small-bodied mammals, canopy openness, and the presence/absence of cattle as predictors of araucaria regenerant density. We found a negative relationship between mammal defaunation and araucaria regeneration. Our results also revealed that the top-10 richest sites in terms of small mammals had a defaunation rate of 0.60 (18% larger than the mean defaunation) and embraced only 100 araucaria regenerants (1.7% of total). Therefore, the mammal defaunation is an important threat to Araucaria Mixed Forest (AMF) functioning and conservation.

Citation

Kotovicz, P. H., Bogoni, J. A., Brum, F. T., Vibrans, A. C., & Carlucci, M. B. (2026). Mammal defaunation negatively affects the regeneration of the critically endangered Araucaria angustifolia. Perspectives in Ecology and Conservation.

TNC Authors

  • Fernanda T. Brum
    The Nature Conservancy