Nutritional correlates of population density across habitats and logging intensities in redtail monkeys (Cercopithecus ascanius)

Food resources are arguably the most common limiting factor for most species, yet little is known about how food quantity and quality interact to determine the size and distribution of wildlife populations. Frugivores may be limited by food quality since fruits, unlike leaves, are typically low in protein and minerals. Understanding the factors influencing frugivore population dynamics is particularly important due to rapid habitat loss and the need to construct informed management plans. Therefore, this study used redtail monkeys in Kibale National Park, Uganda as a model frugivore to (1) compare nutrient intake, reproduction, and habitat use patterns for three redtail groups in an unlogged and heavily logged area; and (2) examine relationships between nutrient intake and redtail population densities across five habitats. Feeding time and intake of crude protein, lipids, and minerals were higher in diets consumed by groups in unlogged areas than heavily logged areas. Intake of both copper and sodium intake was below NRC requirement levels suggested for macaques. Food availability in the unlogged areas was 3.5 times higher than the heavily logged area. Across five study sites, absorbable copper and the ratio of copper to caloric intake in redtail diets were significantly related to redtail population density. These results suggest that food quality is an important factor determining frugivore population density in anthropogenically disturbed frugivore habitats. Copper deficiency, which has been associated with population declines of wild herbivores, has the potential to be a key factor limiting densities of frugivores in tropical habitats.