Predicting folivorous primate abundance: validation of a nutritional model

Area of Science:

• Ecology and animal behavior
• Primate ecology and conservation

Background:

• General models explaining animal abundance are scarce, hindering informed management plans.
• Milton's protein/fiber model suggests food quality predicts folivore biomass, but its generality and assumptions require further examination.
• Previous studies often lacked confirmation of population stability, potentially yielding spurious correlations.

Purpose of the Study:

• To test the generality of Milton's protein/fiber model for predicting biomass in black-and-white colobus monkeys (Colobus guereza).
• To analyze diet selection in colobus monkeys, focusing on leaf maturity and nutritional content.
• To validate the model using stable populations, addressing a critical assumption in prior research.

Main Methods:

• Dietary observations of black-and-white colobus monkeys in Kibale National Park, Uganda, and a forest fragment.
• Analysis of leaf selection based on protein, digestibility, fiber content, secondary compounds, and minerals.
• Population censuses in forest fragments (1995 and 2000) to identify stable populations for model application.

Main Results:

• Colobus monkeys preferentially selected young leaves with higher protein and digestibility, and a better protein-to-fiber ratio.
• Mature leaf nutritional content did not significantly differ from young leaves, except for copper and zinc.
• Biomass in stable colobus populations was strongly correlated with the protein-to-fiber ratio of available trees, explaining 87% of variance.

Conclusions:

• Milton's protein/fiber model is a robust predictor of folivorous primate biomass when applied to stable populations.
• Diet selection by colobus monkeys is driven by nutritional quality, particularly the protein-to-fiber ratio of young leaves.
• The findings support the use of nutritional ecology in developing effective conservation and management strategies for primates.