Mouthing off about developmental stress: individuality of palate marking in the European badger and its relationship with juvenile parasitoses

Fluctuating asymmetry has become a common measure of developmental instability (the inability of individuals to buffer their development from environmental stresses). Here we investigate the symmetry of palatine marking (maculation) in the European badger Meles meles, with regard to the developmental impacts of coccidial endo-parasites. We ask whether maculation is a selected trait, and estimate its heritability. We examine the potential utility of palatine marking as a diagnostic tool for individual identification, and examine its stability over time. The palatine maculations of badger cubs with the highest intensity of endo-parasitic infection were relatively more asymmetrical than those of their less severely infected contemporaries. This weak relationship persisted and strengthened into adulthood, indicating a lasting developmental relationship between physiological challenge and the symmetry of palatine melanin deposition. We did not detect selection for the pattern of maculation. Although size of the maculated area was heritable (h2=0.72 +/- 0.19), its symmetry was not. There was, however, a positive relationship between pair-wise co-ancestry and spatial similarity of these markings. There are no methods currently available to specifically calculate the heritability of 2D traits. Our findings highlight the need to develop new theoretical techniques, potentially elaborating upon the analysis presented. Maculation showed a quadratic trend with age: up to 4 years of age the area of palatine maculation increased in size, but decreased in symmetry; thereafter, in older individuals, size decreased while symmetry increased. Furthermore, despite our evidence for extrinsic factors having some capacity to influence the pattern of maculation over time, these markings were sufficiently stable to facilitate the recognition of individuals in a restricted badger population (< 50 individuals). Such proxies for previous life-history events may provide indicators of the developmental stresses experienced by individuals or populations, informing our understanding of animal societies and the effectiveness of conservation measures.