Chimpanzees as ecosystem service providers: Seed dispersal of an economically important plant resource

Vertebrate-mediated seed dispersal is vital to the maintenance of
diversity in tropical ecosystems, and seed-dispersing animals are
increasingly thought to provide ecosystem services by dispersing the seeds
of plant species utilized by people. However, few studies have
demonstrated a link between vertebrate frugivores and plants used by
people, thus limiting the generalizability of the
seed-disperser-as-ecosystem-service-provider concept. We examined the
effectiveness of western chimpanzees (Pan troglodytes verus) as seed
dispersers (i.e., their influence on seedling recruitment) of an
economically important fruit resource, Saba senegalensis, at the site of
Fongoli, a savanna-woodland environment in southeastern Senegal. The fruit
from the Saba vine is commonly harvested from the wild by local people and
is also an important food item for chimpanzees. We conducted germination
experiments on gut-passed seeds alongside non-gut-passed seeds and
analyzed the germination success of chimpanzee-dispersed seeds in situ. We
also analyzed the effect of habitat type and canopy cover at each seed
dispersal site to determine which sites are most suitable for Saba
germination. Germination trials showed that chimpanzee gut passage and
manual pulp removal increased the likelihood of germination over seeds
left intact. Nearly a quarter of chimpanzee-dispersed seeds germinated in
situ and Saba seeds were distributed non-randomly throughout Fongoli, with
more dispersed seeds found in habitats most suitable for Saba germination.
These results suggest that chimpanzees aid in the early stages of Saba
recruitment and thus provide an ecosystem service via seed dispersal that
may contribute to the well-being of local people.