Primate carcass ecology in the Urema Rift, Mozambique

Primates constitute an integral part of many African ecosystems. In some areas, primate species can be locally very abundant, while in others they are rare or absent. Our central question is: does the abundance of primate bones (or carcasses) reflect the abundance of local living populations? Past bone surveys in Amboseli National Park, Kenya, and Virunga National Park, Democratic Republic of Congo, revealed a positive correlation between carcass abundance and living mammal communities, with a notable exception: a low abundance or absence of primate carcasses when compared to other medium-sized and large mammals. Recent research conducted at Gorongosa National Park, Mozambique, revealed a similar discrepancy between the abundance of primate carcasses and mammalian live census data. This study aims to understand this mismatch between live and dead by examining the influence of ecological factors on primate carcass occurrence and bone distribution in the modern rift ecosystem of Gorongosa National Park. To address these issues, we investigated whether (1) landscape type, proximity to roads, and water sources (pans, rivers, and lakes) predict primate carcass occurrence relative to other mammal taxa, and (2) the accumulation of primate bones significantly differs from that of other mammals in annually flooding and non-annually flooding landscapes (broadly speaking, in the floodplain vs. higher areas). We analysed 26 bones from 18 chacma baboon individuals (Papio ursinus) and 255 bones from 20 other mammal species. Generalised Linear Model (GLM) outputs suggest that permanent water sources such as rivers and lakes are key drivers of primate bone accumulation (p < 0.05). A Fisher's Exact Test indicates that primate bones are deposited more frequently in Rift Valley Riverine & Floodplain landscapes (p < 0.05). Given that baboons regularly cross rivers in Gorongosa, these findings also suggest that crocodile predation may play an important role in determining where baboon carcasses ultimately accumulate, potentially contributing to the observed mismatch between living and dead communities. These findings have important implications for our understanding of primate bone accumulations in the African fossil record, where some palaeontological sites contain abundant primate fossils whereas others preserve few or none.