Ingestion of Ficus enormis seeds by howler monkeys (Alouatta fusca) in Brazil: effects on seed germination

Abstract

Figs (Ficus spp.) have been considered keystone resources for Neotropical frugivores. Such keystone plant resources are characterized by playing important roles in sustaining frugivores through periods of general food scarcity (Terborgh 1986). Many birds and mammals consume figs and disperse their seeds (e.g. Coates-Estrada & Estrada 1986). Howler monkeys (Alouatta spp., Cebidae) are important consumers of figs (Milton 1980). Although it has been accepted that frugivores allow the passage of fig seeds undamaged through their digestive tracts (Janzen 1979, but see Janzen 1981), few quantitative studies exist on the effect of dispersers upon the germination of fig seeds (Coates-Estrada & Estrada 1986, Midya & Brahmachary 1991, Utzurrum & Heideman 1991). Here I report the effect of brown howlers (Alouattafusca Geoffroy) on the germination success of Ficus enormis (Mart. ex Miq.) Miq. This fig species is a strangler tree reaching heights of approximately 15 m, and producing globe syconia (12.70 ?1.02 mm long, 12.82 ?1.19 mm wide, N = 30) which turn brown when mature. Field observations were conducted in the Reserva de Santa Genebra, a tropical upland semideciduous forest (Morellato 1991) in Campinas, Sdo Paulo (220 49' S 470 07' W) between April and June 1992. Ficus enormis fruits at this site are consumed mainly by Alouattafusca, Cebus apella, Artibeus lituratus, Sciurus ingrami (Galetti 1992), and the toucan Ramphastos toco Muller (pers. obs.). Primate faecal samples were collected from the forest leaf litter, mostly below one single fig tree. Seeds used in the germination tests were selected at random from the faeces defecated by a group of five howler monkeys. Seeds used in control germination trials were also randomly chosen from fruits dropped to the ground during primate feeding bouts in the fig crown. The seeds were sown on