Using Africa's protected area network to estimate the global population of a threatened and declining species: a case study of the Critically Endangered White‐headed Vulture Trigonoceps occipitalis
2016
Open Access Article,The White-headed Vulture Trigonoceps occipitalis (WhV) is uncommon and
largely restricted to protected areas across its range in sub-Saharan Africa. We
used the World Database on Protected Areas to identify protected areas (PAs)
likely to contain White-headed Vultures. Vulture occurrence on road transects
in Southern, East, and West Africa was adjusted to nests per km2 using data
from areas with known numbers of nests and corresponding road transect data.
Nest density was used to calculate the number of WhV nests within identified
PAs and from there extrapolated to estimate the global population. Across a
fragmented range, 400 PAs are estimated to contain 1893 WhV nests. Eastern
Africa is estimated to contain 721 nests, Central Africa 548 nests, Southern
Africa 468 nests, and West Africa 156 nests. Including immature and nonbreeding
birds, and accounting for data deficient PAs, the estimated global population
is 5475 - 5493 birds. The identified distribution highlights are alarming:
over 78% (n = 313) of identified PAs contain fewer than five nests. A further
17% (n = 68) of PAs contain 5 - 20 nests and 4% (n = 14) of identified PAs
are estimated to contain >20 nests. Just 1% (n = 5) of PAs are estimated to
contain >40 nests; none is located in West Africa. Whilst ranging behavior of
WhVs is currently unknown, 35% of PAs large enough to hold >20 nests are
isolated by more than 100 km from other PAs. Spatially discrete and unpredictable
mortality events such as poisoning pose major threats to small localized
vulture populations and will accelerate ongoing local extinctions. Apart from
reducing the threat of poisoning events, conservation actions promoting linkages
between protected areas should be pursued. Identifying potential areas for
assisted re-establishment via translocation offers the potential to expand the
range of this species and alleviate risk.
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