Table 1.
Sample characteristics and descriptive statistics for hair cortisol concentrations of hair samples collected from chimpanzee sleeping nests in Uganda.
Fig 1.
Illustration of (a) waning and (b) nest age effect on hair cortisol concentration. (a) Line plot illustrating hair cortisol concentrations (HCC) along four consecutive 1-cm-segments. Data are shown for a representative subsample from 12 chimpanzee sleeping nests with different nest age classes. HCC was significantly different between segments [χ2(3) = 27.7, p < 0.0001, r2 = 0.07] with HCC decreasing towards the distal end of the hair shaft. (b) Boxplots with 1.5 IQR showing HCC from 181 sleeping nests depending on the age class of the nest during hair sampling. Planned contrasts indicated that HCC was significantly higher in new vs. recent and old nests [t(2) = 6.3, p < 0.0001, r2 = 0.95] whereas HCC was only borderline significant between recent and old nests [t(2) = 1.85, p = 0.07, r2 = 0.63].
Fig 2.
Differences in hair cortisol concentrations between seasons and chimpanzee communities with diverse anthropogenic impacts.
Residualized mean hair cortisol concentrations (accounting for nest age effect) with 95% CI in different chimpanzee groups and seasons. (a) Chimpanzees did not exhibit significantly more cortisol due to tourism or logging in comparison to the control group without human contacts. A significant effect of seasonality [F(2,129) = 37.4, p < 0.0001, r2 = 0.18] was presumably unrelated to human impacts. (b) The comparison of hair cortisol concentration between chimpanzees living in an intact forest and those in a forest fragment with severe human-wildlife conflicts revealed significantly elevated HCC in the latter group [F(1,88) = 5.0, p = 0.03, r2 = 0.20].