Baboon Bark Stripping Reduces Pine Plantation Productivity in South Africa

Abstract Bark-stripping by Chacma baboons ( Papio ursinus ) presents a significant threat to the productivity and economic viability of commercial pine plantations in South Africa. This study examined the occurrence, characteristics, and impacts of baboon damage across 23,928 trees from 23 sites monitored for at least five consecutive years. The proportion of affected trees varied widely among sites (8–87%; mean = 37%, SE = 5.36). Stem defects were substantially more frequent among damaged trees (50.8%) than undamaged ones (13.0%), with broken and multiple stems being most prevalent. Damaged trees also exhibited a higher incidence of multiple defects (31%) compared to undamaged trees, where single defects predominated (90%). Mixed-effects model results indicated strong links between tree size and bark-stripping descriptors. Larger trees tended to sustain more lesions, particularly those of moderate severity, as reflected in a positive association between the number of lesions and DBH. In contrast, extreme girdling (≥ 75% bark removal) was associated with reduced DBH, suggesting that while baboons preferentially target larger trees, severe damage subsequently suppresses growth. Overall, damage occurred significantly more often in larger trees (t(36) = 5.65, p < 0.001), with damaged trees averaging 1.04 cm greater DBH than undamaged ones. Girdling severity strongly reduced annual diameter increment (F 492314 = 318.93, p < 0.001), declining from 1.32 ± 0.07 cm yr⁻ 1 in undamaged trees to 0.98 ± 0.01 cm yr⁻ 1 in severely damaged trees. Mortality risk increased by 36% with each severity level (β = 0.31 ± 0.03, p < 0.001), whereas larger trees were less likely to die (β = –0.43 ± 0.01, p < 0.001). These findings demonstrate the significant structural and growth impacts of baboon bark stripping and emphasise the importance of proactive management strategies aimed at reducing damage incidence and maintaining long-term plantation productivity.