Andean bear use of the epiphytic bromeliad Tillandsia fendleri at Quebrada el Molino, Venezuela

Abstract

Epiphytic bromeliads of the genus Tillandsia have been reported as important in the Andean (spectacled) bear diet throughout the bear’s distribution (Mondolfi 1971, 1989; Peyton 1980; Jorgenson and Rodriguez 1986; Rodriguez et al. 1986; Suarez 1989; Goldstein 1990, Rodriguez 1991; Eulert 1995). Epiphytic bromeliads are locally abundant in Andean forests (Gentry and Dodson 1987). Because they are high in soluble carbohydrates, fat, and protein, bromeliads are a nutritious food for bears (Goldstein 1990). Bears often leave sign of their activities in areas where they live; trails, scats, broken branches, claw marks on trees, and beds are common in bear habitats (Burst and Pelton 1983). Andean bears are no exception, leaving abundant sign especially while feeding on epiphytic and terrestrial bromeliads (Peyton 1980, Suarez 1989). In Venezuela, sign of feeding on epiphytic bromeliads by Andean bears has been found in mountain forests between 1,680 and 3,200 m and were the most abundant bear sign found in forests from 2,400 to 2,800 m (Goldstein 1990). Spectacled bears usually produce 2 types of signs at epiphytic bromeliad feeding sites: claw marks on tree bark and piles of bromeliad leaves on the forest floor. Claw marks are visible on tree bark from 40–60 cm above the ground to the branches where the bear fed on the bromeliads. The length and depth of the scars depends on the bark of the tree species. Bears feed on the basal meristematic part of the bromeliads, causing the leaves to drop to the forest floor. Bears have been found to eat 1–10 or more plants at each tree, and Tillandsia fendleri plants have around 50 leaves. Depending on the number of bromeliads eaten, leaves can form a conspicuous carpet on the forest floor. Moreover, usually the central bunch of younger leaves stick together, with bite marks on the white basal meristematic part (Goldstein 1990). Although there are several species of epiphytic bromeliads Tillandsia available in forests between 2,400–3,000 m at Quebrada El Molino (T. compacta, T. complanata, T. tetrantha, T. spiculosa), Andean bears at Quebrada El Molino have been found to only eat the largest species, T. fendleri. They also feed on the fruit of a Lauraceae tree (Beilschmiedia sulcata). In paramo areas, bears feed on the terrestrial bromeliad Puya aristeguietae (Goldstein 1990). T. fendleri plants can reach 2 m in height (including the single central erect inflorescence) and 1 m in diameter (Smith 1971), making them very conspicuous and easily distinguished from smaller Tillandsia species. During work at Quebrada El Molino (Goldstein 1990, 2002), I found that Andean bear T. fendleri feeding sites were mostly located in tall, emergent trees with large canopies and in large trees at the forest–paramo edge, where the abundance of T. fendleri plants was higher (bromeliads/tree x 1⁄4 16.95 [SD 1⁄4 10.89]; diameter at breast height [dbh] x1⁄4 51.84 cm [SD 1⁄4 22.80 cm]; tree height x 1⁄4 10.03 m [SD 1⁄4 3.10]; n 1⁄4 51). Because climbing is energetically costly and the distribution and abundance of bromeliads is clumped, I predicted that Andean bears would maximize expected reward for the effort of climbing trees with T. fendleri, preferentially using trees with the greatest bromeliad loads.