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

Abstract

Aim Promoting population growth of genetically distinct subpopulations of Cape mountain zebra (Equus zebra zebra) is crucial to the survival of the subspecies. Several important Cape mountain zebra reserves are dominated by fynbos vegetation, and population growth is limited by a lack of grassland habitat. A fossil ungulate sequence spanning the last c. 18,000 years is examined to understand the long‐term history of this conservation challenge. Location Boomplaas Cave (BPA), South Africa. Methods The fossil sequence from BPA is examined to reconstruct ungulate community dynamics in relation to climate and vegetation change over the last 18,000 years. Results Ungulates from 18,000 to 12,000 years ago suggest an expansion of open grasslands that supported a grazing ecosystem dominated by an extinct caprine antelope and equid remains attributed to E. zebra and E. quagga. At the onset of the Holocene, the grazing ungulate community disappears and small browsers and mixed feeders dominate the assemblage, indicating the loss of open grassland vegetation. Several open‐habitat grazers go extinct at this time, and Equus persists at much lower abundances. This shift can be explained by global climate change across the Pleistocene–Holocene transition. Main conclusions The fossil sequence supports contemporary observations indicating that access to open grassland is crucial to maintaining large Cape mountain zebra subpopulations. Although fynbos is abundant throughout the historic range of the Cape mountain zebra, fossil evidence suggests that such vegetation is unlikely to support dense populations. It has been suggested that the acquisition of agricultural lands that were historically converted to open grasslands for livestock could promote Cape mountain zebra population growth. Results presented here support this management option, as the open grasslands in these converted landscapes likely approximate the vegetation structure during latest Pleistocene, when grasslands were widespread and grazing ungulates abundant.

Climate change and faunal turnover: testing the mechanics of the turnover-pulse hypothesis with South African fossil data

“…As sea level rose, the band of fynbos and other shrubby vegetation types moved northward across the formerly grassy coastal lowlands. This is consistent with fossil mammal sequences spanning the PleistoceneHolocene transition, which show the replacement of open-habitat grazers by small browsers typical of CFR shrublands, with an essentially modern fauna in place by~5000 years ago (Schweitzer and Wilson 1982;Klein 1983;Faith 2012b). There is also evidence for comparable shifts in faunal composition across glacial-interglacial stages earlier in the late Pleistocene (Klein 1983).…”

“…Thus, paleoenvironmental records independent of the large mammal record from both the SCP and WCP provide evidence for an expansion of grasslands. Consistent with this vegetation change, fossil evidence indicates that the large mammal community that inhabited the exposed coastal plain was species rich and dominated by large grazing ungulates, including equids and alcelaphine antelopes (Schweitzer and Wilson 1982;Klein 1983;Klein and Cruz-Uribe 1987;Rector and Reed 2010;Faith 2011b). Grazing species may have migrated seasonally across the coastal platform, following the winter rains in the WCP and the summer rains along the eastern SCP (Marean 2010;Faith and Thompson in press).…”

“…We note that Boomplaas Cave is not located on the SCP proper, but rather is located~80 km inland on the flanks of the Swartberg Mountains (Cape Fold Belt). Its inclusion in the broader SCP sample is justified by the fact that it shares most of the same species present in other SCP sites, suggesting interchange between the two regions, and because it shows a similar faunal transition from grasslands to shrublands across the Pleistocene-Holocene transition (Avery 1982;Klein 1983;Faith 2012b).…”

“…Micromammal assemblages from Byneskranskop 1 and Boomplaas Cave (SCP and Cape Fold Belt) indicate peak frequencies of grassland species during the LGM-Lateglacial (Avery 1982). These vegetation shifts are likely related to altered rainfall regimes and diminished atmospheric CO 2 concentrations (Chase and Meadows 2007;Faith 2013). Thus, paleoenvironmental records independent of the large mammal record from both the SCP and WCP provide evidence for an expansion of grasslands.…”

“…Grazing species may have migrated seasonally across the coastal platform, following the winter rains in the WCP and the summer rains along the eastern SCP (Marean 2010;Faith and Thompson in press). Given the presence of grassland faunas on the coastal lowlands and in the highlands of the Cape Fold Belt (Klein 1983;Faith 2012b), fynbos and its associated browser-dominated mammal community likely occurred along a narrow zone adjacent to the expanded paleocoastline Marean 2010;Compton 2011). FIGURE 3.…”