Distance from available surface water of mammals in Ruaha National Park

In Africa, burgeoning human populations promote agricultural expansion and
the associated demand for water. Water abstraction for agriculture from
perennial rivers can be detrimental for wildlife, particularly when it
reduces water availability in protected areas. Ruaha National Park (Ruaha
NP) in southern Tanzania, one of the largest parks in Africa, contains
important wildlife populations, including rare and endangered species. The
Great Ruaha River (GRR) is the main dry-season water source for wildlife
in the Park. Water offtake from this river for large-scale irrigation and
livestock production up-stream of the Park has caused large expanses of
this formerly perennial river within the Park to dry out during the dry
season. The dry season distribution of a species in relation to surface
water is considered an indicator of its dependence on water and ability to
cope with the loss of surface water. We investigated how diminishing
surface water availability during three dry seasons (2011–2013) affected
herbivores’ distance to water in Ruaha NP. The distance held by herbivores
to water is shaped by a range of factors including dietary category. We
determined changes in the locations of available surface water throughout
the dry season using standardized ground transects, close to and leading
away from the GRR, to map the locations of nine herbivore species.
Functional responses of herbivores, i.e. their change in distance to water
between early and late dry season, indicated that distance to water was
(i) shortest in buffalo and waterbuck (grazers), (ii) similar for plains
zebra (grazer), elephant and impala (mixed feeders), (iii) larger in
giraffe and greater kudu (browsers) and (iv) largest in generalist feeders
(warthog, common duiker). The substantial species’ differences in surface
water dependence broadly fit predicted species differences in their
ability to cope with anthropogenic reduction in surface water in Ruaha NP.