Assessment of wildlife populations trends in three protected areas in Tanzania from 1991 to 2012

Abstract

Wildlife populations have been experiencing declines across western, central and eastern Africa. In Tanzania, a national wildlife policy was instituted in 1998 to increase protection of wildlife. We assessed (i) the extent to which large herbivore populations have continued to decline in density and distribution within three representative protected areas (PAs) since the implementation of the wildlife policy; (ii) how consistent rates of decline were among the PAs, and between inside the PAs or land bordering these PAs; and (iii) how similar changes in abundance have been among herbivore species or groupings of species. We used aerial census data from 1991 to 2012 for the Tarangire, Ruaha-Rungwa and Katavi-Rukwa PAs for our assessment. Population densities of three of six species or groupings of species dropped by 7.3 ± 3.4% to 11.7 ± 5.8% per year across the three PAs, both inside and outside. Similarly, the extent of the range occupied by these species or groupings in these PAs decreased by 92.3 ± 103.0% to 95.7 ± 102.6% per year. These patterns suggest that the wildlife policy has yet to achieve its aim of reversing the habitat changes and illegal harvests affecting these species.