highly significantp < 0.001
The minimal model for fur and skin, which included age categories 1–3 as a factor, explained 42.74% ( p < 0.001) and 22.23% ( p < 0.05) of data variability, respectively, with a highly significant difference found between age groups 1 and 3 ( p < 0.001) and no difference between groups 1 and 2 (Fig. 2a, b ).