DIET OF THE CAUCA GUAN: EXPLOITATION OF A NOVEL FOOD SOURCE IN TIMES OF SCARCITY

Abstract

Although exotic species may have a negative impact on native organisms, they can in some cases provide abundant resources. Use of these resources may have important implications for habitat use, movement, and space requirements of native animals, and ultimately for population dynamics. We describe the diet of a population of the narrowly endemic Cauca Guan (Penelope perspicax) in the Colombian Andes. This guan demonstrates plasticity in its eating habits, feeding on an exotic tree species during periods of food scarcity. Based on direct observations and analysis of fecal samples over a one-year cycle, we found that guans fed on 89 species of fruits but also included foliage, flowers, and invertebrates in their diets. Guans fed on fruit species in proportion to their availability but favored some species with high fruit production or prolonged fruiting. Fruit availability, measured both in numbers of species and biomass, varied throughout the year, with a low in September-December. During the period of low fruit availability, guans congregated in large numbers at a Chinese ash (Fraxinus chinensis) plantation, where they fed on young leaves in large quantities. Ash was planted at this site over 40 years ago as part of a reforestation program, and plantations are invaded by native vegetation. Guans are abundant at this site, and seasonal consumption of ash foliage, a concentrated and abundant food source, may have influenced local population dynamics.