Extinction of the blue antelope Hippotragus leucophaeus: modeling predicts non-viable global population size as the primary driver

Abstract

The extinction of the blue antelope Hippotragus leucophaeus in 1800 is poorly documented and understood, and has been ascribed to a combination of habitat loss and overhunting by early European colonists with firearms. We modeled the distribution and abundance of this species to gain insight into the extinction process. Model outputs indicate that prior to the arrival of European colonists, blue antelope were restricted to a small area (c. 4,300 km 2 ), with an estimated population of only 370 individuals. We conclude that the historical population of blue antelope was functionally an island population in terms of demographic and genetic processes, by virtue of its limited distribution, small size and lack of metapopulation processes. The small population (effective population size *100 individuals) would have been vulnerable to stochastic effects and was probably trapped in an extinction vortex. Hunting pressure by European colonists merely provided the coup de grace to a species already on the brink of extinction.

Fossil evidence for seasonal calving and migration of extinct blue antelope (Hippotragus leucophaeus) in southern Africa

“…Although we agree with Kerley et al . () that long‐term processes are largely responsible for the demise of the blue antelope, it may be premature to discount the impacts of European colonists. The evaluation by Kerley et al .…”

“…Other contributing factors could include hunting and landscape transformation by European colonists, the introduction of livestock c. 2000 years ago, or long-term vegetation change. Kerley et al (2009) argue that the historical range of blue antelope was too small to support a viable population, in which case European colonists were incidental contributors to the extinction of a species that was already doomed. The crucial question raised by this result is why the blue antelope range had declined to this point, especially in light of the broader distribution observed in south-coast fossil deposits from the last 2000 years (e.g.…”

“…at Die Kelders Cave and Nelson Bay Cave). Kerley et al (2009) suggest that long-term processes (e.g. vegetation change) may be responsible, and this is supported by the steady decline in blue antelope abundances through the Holocene at Nelson Bay Cave (Klein, 1983;Faith, 2011b).…”

“…Previous studies have invoked several potential mechanisms to account for the extinction of the blue antelope, including overhunting by European colonists, competition and habitat degradation associated with the spread of pastoralism, and habitat loss due to long-term environmental change (Klein, 1974(Klein, , 1987Robinson et al, 1996;IUCN SSC Antelope Specialist Group, 2008;Kerley et al, 2009;Faith, 2011b). A better understanding of how these processes might have contributed to the blue antelope's extinction, however, requires an improved understanding of its ecology.…”

Palaeozoological insights into management options for a threatened mammal: southern Africa’s Cape mountain zebra (Equus zebra zebra)

“…Palaeoecological evidence indicates that these taxa were grazers with a preference for open and grassy habitats (Marean, 1990;Klein, 1994;Lee-Thorp & Beaumont, 1995;Brink, 1999;Faith, 2011a,b). Also present is the extinct blue antelope (Hippotragus leucophaeus), a grazer that disappeared in historic times c. 1800 AD (Klein, 1974;Kerley et al, 2009;Faith, 2011b). Figure 2 illustrates the changing abundance of bovids and equids through time at BPA.…”