Aspects of the ecology of fruit bat (eidolon helvum) in the University of Energy and Natural Resources, Sunyani

Aspects of the ecology of straw coloured fruit bats (Eidolon helvum), including population dynamics, seed dispersal and effect on the roosting trees, were investigated in the University of Energy and Natural Resources, Sunyani from January 2013 to July 2014. The Continuous Point Count Method was used to estimate the monthly population size of E. helvum. Using 64m2 (4m x 4m) quadrats and 32 seed traps made from plastic sheets, the contribution of dispersed plant species to the total undergrowth plant cover in the area was sampled and catalogued to show the contribution of undergrowth from bat droppings in the area. Using six (20m x 20m) sample plots each for areas occupied by bats and areas unoccupied by bats, basal area, canopy, and heights of identified trees with DBH ≤ 1m were measured to show the impact of bats on the roosting trees. The results indicated that: (1) bats were present in the study area throughout the survey period, however, their numbers varied between months. The bat population estimates in 2013 were high in March (180,000) and December (240,000), but between the months of May to October their population were low, (12,400; 15990; 12,500; 18,500; 10,600 and 28,500) respectively, in the colony. This pattern is similar to the year 2014. The mean number of bats per month was estimated at 55,469.55 bats (S.E=4.34, CV=8.68%) for the study period. The mean population estimates in the dry season count was 85,955.5±87,272.3 whilst the mean population estimate in the rainy season count was 46,932.3±58,122.9. However, there was no significant difference between the mean dry and rainy season population count of bat in the study area, t(8) = -0.922, p>0.05(2) Undergrowth plant species sampled indicated that the percentage contribution of some of the species dispersed by bats were Mallotus opposotifolia,(16.1%), Broussonetia papyrifera (10.6%), Ficus exasperata (6.6%), Solanum erianthum (6.2%) and Morus mesozygia (4.6%). These plant species altogether contributed 1.7% of the seedling composition in the undergrowth in the study area. These plants contributed to the ecological improvement by increasing the biodiversity in the study area through increased species cover and regeneration of dispersed species of the roost site.(3) Height and basal area of trees were the only factors that led to tree selection as roost by bats in the occupied zone. Trees in bat occupied areas, showed significant damages by bats through premature defoliation as well as loss of branches which resulted in reductions in canopy foliage of host trees, compared to the bat unoccupied areas. The main physical plant features that were affected are the tree canopy size and canopy cover. These bats have been known to have limited roost sites, so good management of their population to reduce threat to their survival is important. Sound strategies like monitoring population, roosting trees and habitat, in relation to the climatic conditions are required to be documented overtime to promote sound decisions and add to scientific knowledge to the study of bats.

Source: KNUST