Abstract:
Elephants are essential ecological engineers, creating and maintaining landscape
structure and ecosystem function. The recently distinguished and critically endangered
forest elephant is currently classified as a selective, non-destructive
frugivorous
browser that maintains forest diversity, while the savanna elephant is a mixed
feeder, often pushing over trees while maintaining grasslands. The presence and diets
of forest elephants on grasslands and the potential maintenance of these systems
remain largely unexplored. In the ecotone between the Guinea-Congolian
forest and
Sudanian-Guinean
savanna ecosystems in Garamba National Park, DRC, we investigated
forest elephant diet selection as a function of sex, age, and habitat using diet
DNA (dDNA) metabarcoding of non-invasively
collected dung. GPS collar data were
used to determine annual habitat use. Dietary niche partitioning was assessed among
megaherbivores in the grasslands. Fecal samples represented the diet of individuals
within each habitat, providing valuable insight into the plant biodiversity. Ecological
patterns of diet were also revealed using a taxonomically free exact sequence variance
approach, highlighting useability in a poorly characterized region. In the early wet
season, these typically frugivorous forest elephants were consuming mostly grasses
in both the woodland and grassland habitats and showing no sexual dimorphism in
diet selection when in the same habitats. However, males were greater risk-takers,
entering the human-altered
landscape to forage on fruit. The forest elephants play
a distinctive role within this tropical grassland when compared to other megaherbivores
and utilize the unique ecosystem throughout the year. This elephant population is exhibiting behavioral plasticity and shifting their gardening efforts to a novel resource
in the grasslands as opposed to their standard role in the forests, which is key
to understanding their impact as ecosystem drivers within this landscape. This shift in
behavior may result in this recovering elephant population playing a functional role in
the restoration and maintenance of these grasslands.
