Early Recruitment Constraints in Marula (Sclerocarya birrea caffra), a Keystone Savanna Tree: Ex Situ Rodent Feeding Trials and In Situ Seedling Scarcity

Mammals influence savanna tree recruitment through seed handling, granivory, and browsing, but their relative contributions across early life stages remain uncertain. We examined marula (Sclerocarya birrea caffra) in South Africa’s Greater Kruger Ecosystem using captive rodent feeding trials (2014 and 2016) and subsequent seedling surveys and antelope camera-trap monitoring at 20 habitat-stratified sites (2019–2022). In 2014 trials, marula seeds experienced greater interaction and visible damage than alternative tree species, whereas 2016 mixed-effects analyses found lower marula consumption severity than knobthorn. Differences in seed sources, scoring methods, supplementary food, and tree species offered precluded direct comparisons between years. Across captive seedling trials, 44 of 80 seedlings (55%) sustained presumed lethal damage, although mortality was not confirmed. A mixed-effects analysis restricted to 59 seedlings exposed to 29 Namaqua rock mice found no significant tree-species effect on presumed lethal damage (likelihood-ratio χ2(3) = 2.840, p = 0.417). Field surveys documented 14 marula seedlings in 2019/20 and 48 in 2021/22. Antelope site-use varied among vegetation communities, while kudu site-use also differed with season and distance to water. Sparse seedling observations and unstable models prevented reliable inference about relationships between antelope site use and marula recruitment. Together, these complementary studies document rodent damage and local seedling scarcity while highlighting the need for direct tests of wildlife-driven recruitment limitation.