Impact of Eidolon helvum on roost trees on UENR campus

Abstract

Four sample plots, each of size 20m by 20m were systematically distributed in two strata (i.e. two plots in bat-occupied zone and the remaining two plots in bat-unoccupied zone, to serve as control units). Using six (20m × 20m) sample plots each, basal area, canopy, and heights of trees with DBH 1m were measured. Fourteen individual trees were recorded in the bat unoccupied zone, resulting in only seven tree species. On the other hand, 16 tree species, corresponding to a total of 25 trees were recorded in the bat occupied zone. Albizia zygia, Antiaris toxicaria, Azadiractha indicia, Holarrhena floribunda, Morinda lucinda, and Sterculia
tragacantha were common to both zones. The Shannon Wiener species diversity index was found to be higher (H1=1.92) in bat occupied zones and lower (H1=1.45) in bat-unoccupied zone. Estimates of tree basal area and tree height were much higher in bat occupied zones compared to bat-unoccupied zones. (Mann-Whitney U test: U = 573.0, p < 0.05), tree basal area (U = 674.0, p < 0.05), tree height (U = 632.0, p < 0.05) and tree canopy cover (U = 329.0, p < 0.05). Holarrhena floribunda (0.34 m²/h) and Ceiba pentandra (0.22m2/ha) contributed the largest basal area (32.94% of the total basal area) whilst Senna siamea (0.01m²/ha) and Tectona grandis (0.01m²/ha) yielded the smallest basal area (1.17%). In general, bats seem to greatly patronize areas with higher densities of tall trees than relatively open areas with shorter trees.