Frugivores at a Fruiting Ficus Vine in a Southern Cameroon Tropical Wet Forest

Abstract

A fruiting Ficus sp. vine in a southern Cameroon tropical wet forest was monitored for 57.75 hours over a 9-day period in early February 1979. Avian frugivores observed eating figs included one fruit pigeon, four hornbill, and three greenbul species. Two species each of monkeys and squirrels also ate figs. Greenbuls were present at 59 percent of the censuses, fruit pigeons at 12 percent, and hornbills at 11 percent. Mean foraging group sizes for greenbuls, fruit pigeons, and hornbills were 1.7, 2.3, and 2.0, respectively. Greenbuls ate an estimated 17,332 fruits over an 8 day period, fruit pigeons 4769, hornbills 2534, and Greater White-nosed Monkeys 811. BIRDS EXPLOITING ABUNDANT, though temporary, singletree fruit crops in the neotropics have been the subject of numerous short-term studies in recent years (see references in Fleming 1979). One such study has been done on New Guinea birds (Terborgh and Diamond 1970), and a longer, broader investigation exists for Malaysia (McClure 1966). More recently, detailed studies have been undertaken on frugivores associated with neotropical trees producing high quality fruit (sensu McKey 1975) (e.g., Howe 1977; Howe and Vande Kerckhove 1979, 1981) and low quality fruit (Howe 1980). Analogous information from the African tropics is conspicuously scarce. Figs (Ficus spp.) are common in tropical, forested regions. Yet, there has been no detailed study of animals visiting even a single fig tree and thus serving as the potential dispersal coterie UJanzen 1979). I report here on rates of exploitation by bird and diurnal mammal frugivores of the large crop of a Ficus vine in a southern Cameroon, tropical, wet forest. STUDY SITE AND METHODS Observations were conducted in primary rain forest bordering Lake Tissongo in the Douala-Edea Faunal Reserve, located about 35 km SW of Edea, Cameroon, and 20 km from the Gulf of Guinea. The Ficus sp. vine was growing at a height of about 20 m in the crown of a slightly emergent leguminous tree. I estimated projection of the vine onto the forest floor as subcircular, 7 m in diameter, and the vertical space occupied in the supporting tree's crown as 3 m. Syconia (fig fruit) were about 1 cm in diameter, spheroidal, and dark red when ripe. Upon my arrival at the site on 28 January 1979, spontaneous dropping of fruit was intermittent. Fruit fall peaked 3-5 February and had declined sharply when observations were terminated on 8 February. Hence, I am confident that I monitored most fruiting of the vine. The fig was monitored for a total of more than 57 hr over a 9-day period, 43 hr of which occurred during the final 4 days. Casual observations were made on bird and mammal visitors from 30 January through 3 February and lengths of foraging bouts by individuals of several species were noted on these days. I conducted 177 censuses on 4-7 February, counting individuals of all species present every 15 min from early morning (about 0630) to late afternoon (about 1730). I noted very few individuals arriving, foraging, and leaving within the 15 min interval between censuses, thus verifying validity of counts made at this interval. Weather data were collected in a nearby forest clearing at the field research station of the Wisconsin Regional Primate Center. Early morning and late afternoon temperatures varied between 22-27?C and midday temperatures between 26-35?C. Two days were cloudless, the remainder hazy to cloudy. There was a trace of rain on 4 days, and 1.5 cm of rain fell on 2 February, all precipitation occurring during daylight hours.