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

Abstract

Aim Palaeoecological data are crucial to understanding the historical extinction of the blue antelope (Hippotragus leucophaeus). This study examined late Quaternary fossil evidence bearing on the blue antelope's calving and migratory habits. Location Cape Floristic Region (CFR), South Africa. Methods Blue antelope mortality patterns were reconstructed from dental remains from fossil assemblages spanning the last c. 200,000 years and located in the CFR's winter and year‐round rainfall zones. Two demographic measures were examined: (1) the frequencies of juveniles relative to adults; and (2) the frequencies of neonates relative to older juveniles. Geographical trends were examined across a longitudinal gradient of decreasing winter rainfall and increasing summer rainfall. Results There was a significant longitudinal trend in the blue antelope mortality data, with juveniles and neonates declining in frequency from west to east. This suggests that calving occurred primarily in the winter rainfall zone, probably during the winter months when seasonal rains promoted the growth of C3 grasses. The summer drought and lack of adequate forage forced blue antelope to migrate east, in time with summer rainfall and the increased availability of C4 grasses. The migration route probably depended in part on reduced sea levels during glacial phases of the Pleistocene. Main conclusions Blue antelope were probably migratory. Rising sea levels at the onset of the Holocene disrupted their migration routes, limited access to west‐coast calving grounds, and fragmented populations. Such disruption would have devastated the blue antelope population and contributed to its vulnerability to extinction. Blue antelope survived previous marine transgressions, however, suggesting that other factors played a role in its demise. Agricultural expansion early in the colonial era may have further disrupted migration routes and played an important role in its extinction.

Strontium isotope investigation of ungulate movement patterns on the Pleistocene Paleo-Agulhas Plain of the Greater Cape Floristic Region, South Africa

“…These rainfall conditions were hypothesized to provide the push and pull for a classic migration ecosystem on the Paleo-Agulhas Plain in the Pleistocene whereby animals moved east and then west to take advantage of summer and winter rains and green grass, respectively (Marean, 2010;Marean et al, 2014). The mortality patterns of fossil specimens of the blue antelope Hippotragus leucophaeus from sites along the south coast are consistent with an east-west migration (Faith and Thompson, 2013). An alternative hypothesis is that animals moved along a north-south axis, migrating from the coastal plains, through mountain passes of the Outeniqua Mountains, and into the Little Karoo intermontane basin.…”

Continuous vegetation record of the Greater Cape Floristic Region (South Africa) covering the past 300 thousand years (IODP U1479)

“…Mapping of the glacially exposed PAP places the grasslands mainly in the central and eastern part of the plain with Fynbos and Renosterveld vegetation dominating the western part during the LGM Marean et al, 2020). It is envisaged that the PAP would have harboured grazers migrating from the west in winter to the east in summer and back to make optimal use of grazing opportunities between winter rainfall and summer rainfall regions (Marean, 2010;Faith and Thompson, 2013;Copeland et al, 2016). However, a test of this proposed migration using https://doi.org/10.5194/cp-2021-93 Preprint.…”

Palaeoecology of giraffe tracks in Late Pleistocene aeolianites on the Cape south coast

“…The giraffe populations of the Late Pleistocene southern Cape likely occurred on the wide, alluvial valleys of the aforementioned rivers, which meandered across the low-gradient Palaeo-Agulhas Plain 6 , when it was exposed during glacial conditions 52 . While appropriate edaphic conditions, namely fertile alluvial soils 55 , certainly existed to support giraffe habitat at this time, there is less certainty regarding the climate.…”

“…9 An analysis of age at death data of fossil blue antelope is consistent with a seasonal migratory movement. 52 The emergence of the Palaeo-Agulhas Plain is strictly controlled by sea level and the position of resultant shorelines. 5,53 Interpretation of marine geophysical data in the Mossel Bay area suggests a low-relief 'plains' landscape offshore of the southern coastal plain 16,6 , and this region was dominated by shallowly incised rivers with vast floodplains and wetlands.…”