Management of spontaneous agroforestry woody plant species and role of fruit bats in their seeds dispersal in the Biosphere Reserve of Pendjari (Benin).
DJOSSA Bruno (2007)
PhD, University of Abomey-Calavi
Plant-animal interaction focussing on fruit bats (Pteropodidae) research in land use context was carried out in Pendjari Region (Biosphere Reserve of Pendjari (BRP) and surrounding village territories) in north-western Benin. Data revealed that agriculture and agroforestry practices reduced woody plants diversity and density and population structure of bats was also affected in these areas. However, local populations preserve useful woody plants with detriment to other plant species. Shea tree (Vitellaria paradoxa) was one of these plants because of its socio-economical importance. Individuals in disturbed areas (village territories) had the biggest diameter and were more productive than those in undisturbed areas (BRP). Although this good conservation situation of this plant species, assessment of its population structure showed that juveniles of dbh 5-10 cm weren’t well represented in disturbed areas compared with undisturbed areas. Spatial distribution pattern analyses showed a weak aggregation pattern in adult individuals and absence of positive association (attraction) between adult and juvenile shea trees in disturbed areas in contrary to what was observed in undisturbed areas demonstrating human’s impacts. Impact on woody plants had direct link with feeding resources availability for fruit bats as it depends on woody plants diversity and abundance.
Capture effort was 7,265.5 hours corresponding to 605.5 mist net nights and 1,293 nets of 12 m length were used. A total of 1,552 bats were collected (1,217 fruit bats and 335 insectivores) distributed in 8 families (100 % of known families in Benin), 22 genus and 28 species (56 % of known species in Benin). Three new species were recorded increasing species richness of 6 % with the total species number of bat in Benin passing from 47 to 50. These new species were Hypsignathus monstrosus, Lissonycteris angolensis and Myonycteris torquata (all Pteropodidae species). The Capture success was similar between disturbed and undisturbed areas (2.96 vs 2.13 bats / net night) even for fruit bats and insectivores considered separately, but fruit bats diversity was higher in undisturbed areas (7 species vs 5 in disturbed areas). In term of the relative abundance, fruit bats species reacted differently to disturbance: Epomophorus gambianus was more abundant in disturbed areas, Nanonycteris veldkampii preferred undisturbed areas whereas Micropteropus pusillus showed similar abundance in both areas. Rare species (Rousettus aegyptiacus, Hypsignathus monstrosus and Lissonycteris angolensis) were only collected from BRP.
Nine (9) different fruits species were recorded for fruit bats through faecal samples and from feeding roosts. These species were Annona senegalensis (Annonaceae), Balanites aegyptiaca (Balanitaceae), Diospyros mespiliformis (Ebenaceae), Ficus glumosa var. glaberrima, Ficus spp. (Moraceae), Lannea microcarpa (Anacardiaceae), Sarcocephalus latifolius (Rubiaceae), Vitellaria paradoxa (Sapotaceae) and Vitex doniana (Verbenaceae). Shea fruits were the most consumed during wet season by the most abundant fruit bats species which relative abundance increased in this season. However our results showed that this increase in abundance didn’t match exclusively with this plant fruiting period. Migratory species like N. veldkampii increased its abundance during wet season when Myonycteris torquata and Eidolon helvum, also migratory species, were back only during this season.
Consuming shea fruits flying foxes (fruit bats) dispersed seeds and that phenomenon is important for the natural regeneration and for the long-term conservation of this plant species that contributes substantially to rural population household’s incomes. The seed dispersal is also important for the shea tree, as local populations not yet cultivate it.
Key words: Bats, seed dispersal, vegetation, shea tree, conservation, B.R. of Pendjari and village territories, Bénin.