The Effects of Leopard Predation On Grouping Patterns in Forest Chimpanzees

Abstract

[During a 5-year period, 29 interactions between chimpanzees and leopards have been observed or inferred in the tropical rainforest of the Tai National Park, Cote d'Ivoire. Chimpanzees chased away leopards in 9 cases, rescued alarm calling chimpanzees in 11 cases (in 4 of these footprints or growls of leopards were noted), 9 times leopards attacked chimpanzees, injuring 6 of them and killing 4. Two of the latters were most certainly eaten by the leopard later. Predation by leopards is estimated to be the first cause of mortality in the Tai chimpanzees and individual chimpanzees may experience a risk of predatory attack of 0.30 per year and a mortality risk of 0.055 per year. Tai chimpanzees adapt specifically their grouping patterns to food availability and to predation: with abundant food and low predation, party size increases and mixed parties are more frequent, whereas with the same food condition but with high predation, party size decreased and all-male party types increase. Comparisons with data on grouping patterns from Gombe and Mahale chimpanzees living in more open habitats support the hypothesis that this species adapts itself to leopard predation which is known to be lower in savanna habitats. The grouping patterns of the bonobo in Lomako forest seem more similar to Tai than to Gombe or Mahale chimpanzees, suggesting an analogous adaptation to high predation pressure., During a 5-year period, 29 interactions between chimpanzees and leopards have been observed or inferred in the tropical rainforest of the Tai National Park, Cote d'Ivoire. Chimpanzees chased away leopards in 9 cases, rescued alarm calling chimpanzees in 11 cases (in 4 of these footprints or growls of leopards were noted), 9 times leopards attacked chimpanzees, injuring 6 of them and killing 4. Two of the latters were most certainly eaten by the leopard later. Predation by leopards is estimated to be the first cause of mortality in the Tai chimpanzees and individual chimpanzees may experience a risk of predatory attack of 0.30 per year and a mortality risk of 0.055 per year. Tai chimpanzees adapt specifically their grouping patterns to food availability and to predation: with abundant food and low predation, party size increases and mixed parties are more frequent, whereas with the same food condition but with high predation, party size decreased and all-male party types increase. Comparisons with data on grouping patterns from Gombe and Mahale chimpanzees living in more open habitats support the hypothesis that this species adapts itself to leopard predation which is known to be lower in savanna habitats. The grouping patterns of the bonobo in Lomako forest seem more similar to Tai than to Gombe or Mahale chimpanzees, suggesting an analogous adaptation to high predation pressure.]