Why do primates bark-strip pines in plantations? Seasonal profitability as a key driver

Abstract

Bark-stripping by mammals is a widespread conflict in forestry plantations, yet the mechanisms driving this behaviour remain poorly understood, leading to ineffective mitigation attempts. Primates frequently bark-strip pines in plantations, generating economic losses and hindering human–wildlife coexistence. We studied black capuchins (Sapajus nigritus) bark-stripping in loblolly pine (Pinus taeda) plantations in Argentina to evaluate two hypotheses: (1) the fallback food hypothesis, predicting bark-stripping when native fruits are scarce; and (2) the pine seasonal profitability hypothesis, predicting bark-stripping when inner bark profitability (energy gain per handling time unit) surpasses a threshold. Over two years, we monitored monthly bark-stripping intensity along 40 transects of 50 pines each, located within the home ranges of four capuchin groups. We quantified inner bark thickness, sugar content (energy), and peeling force (handling time) to estimate profitability, and calculated a native fruits energy availability based on phenology, basal area, and sugar content. We used Generalised Additive Models to test both hypotheses. Across the study period, 38.5 % of trees experienced some degree of barkstripping. Bark-stripping showed a marked seasonal peak in late winter and early spring (July–October), mainly affecting medium-aged stands (5–9 years). During these months, thicker bark and reduced peeling force temporally increased profitability, whereas sugar content showed no clear seasonal trend. The best-supported model included inner bark profitability alone. These findings support the pine seasonal profitability hypothesis and provide a predictive framework for forest management by clarifying the mechanisms behind barkstripping and targeting the behaviour spatially (medium-aged stands) and temporally (July–October).