Effects of elephant feeding on species of acacia along the Great Ruaha River in Ruaha National Park, Tanzania

Abstract

This study compared the effects of elephant browsing and response between Acacia tortilis and A. kirkii in Ruaha National Park. A total of 30 belt transects were randomly placed in an area of 38.8 km2 on the northern bank of the Great Ruaha River, where 1007 Acacia trees were assessed for elephant damage. Damage was assessed basing on six browsing categories and four debarking classes. There was no significant difference in browsing (F1, 10 = 0.6, p>0.05) and debarking (F1, 6 = 0.16, p > 0.05) between A. kirkii and A. tortilis. Trees were classified into three height classes and twelve diameter classes to determine population structure. A total of 3613 trees < 1 m in height were recorded to represent response in addition to coppices; and a significant difference between the two species was observed only in regeneration potential (F1,58 = 41.4, p < 0.05). Significant difference was also observed in population structures (F1, 58 = 42.08, p < 0.05). However, the low regeneration potential, relatively high proportion of severely browsed trees and restricted distribution of A. kirkii in the study area could make it vulnerable to elephant feeding than A. tortilis. The high A. tortilis regeneration potential suggests the likelihood that the area between Msembe and Lunda could become an Acacia bush or woodland if fire is controlled. The study concludes with recommendations for further studies on the variation in vegetation utilisation by elephant along the Great Ruaha River, suppressed regeneration of Acacia trees at Msembe, effects of fire and small browsers on Acacia species as well as continuous monitoring of vegetation and animal trends.