Grouping patterns within the genus
Tragelaphus suggest that species inhabiting open areas tend to live in larger groups, while species preferring dense habitats live solitarily
or in small family groups. We asked if similar variation would be concealed in the within-species variation of bushbuck (
Tragelaphus scriptus). Recent molecular phylogeographic analyses revealed several locally adapted forms of bushbuck in different ecoregions on
the African continent. We compared group sizes of south-eastern bushbuck (
Tragelaphus sylvaticus) among six different populations (“ecotypes”). To date, most data on the social organization of bushbuck have been collected
from only one population in Queen Elizabeth National Park (QENP) in Uganda. This particular population, however, inhabits
an unusual—comparatively open—habitat type, while bushbuck otherwise inhabit dense habitats, leaving doubt whether data collected
in QENP are representative of the entire species. We, therefore, compared grouping patterns between ecotypes inhabiting rather
open habitats (e.g.,
dianae and
haywoodi) and ecotypes occupying rather dense habitats (e.g.,
massaicus and
ornatus). In bachelor groups and in all-female (spinster) groups, single sightings were the most frequent “group type” in all populations
examined. We detected no significant difference among ecotypes in relative frequencies of group size categories in the case
of bachelor groups. Spinster group sizes were slightly (albeit significantly) smaller in QENP than in all other areas. Moreover,
a comparison of two areas inside (low human pursuit) and outside Lake Mburo National Park (high hunting pressure) in Uganda
revealed no significant difference in grouping patterns in response to human pursuit (as reported for impala [
Aepyceros melampus] inhabiting the same area). Altogether, our results suggest that group sizes in bushbuck are not dependent on the habitat
type they inhabit; neither does human nuisance have an impact on grouping patterns. Hence, an “almost solitary” lifestyle
appears to be a characteristic of the entire taxon.
Keywords Antelopes - Ecological diversification - Social organization - Group size - Group composition
Communicated by P. Heeb