Sexual dimorphism of craniomandibular size in the Eurasian otter, Lutra lutra, from South Korea.

Sexual size dimorphism of craniomandibular morphology of the Eurasian otter Lutra lutra in South Korea was analyzed using linear measurements. In total, 32 skulls (18 males and 14 females) and 22 linear measurements (16 cranial and 6 mandibular measurements) were used. Our results showed statistically significant sexual dimorphism between male and female skull size. Multivariate analyses using the cranial and mandibular traits showed significant differences between the sexes, respectively. The most dimorphic trait was ectorbital breadth (EOB), and the EOB of the male was approximately 10% greater than that of the female. This type of sexual size dimorphism, in which males are generally larger than females, is a general pattern shown in family Mustelidae. Several researchers have suggested various hypotheses about the factors causing sexual size dimorphism, i.e., 'resource partitioning model' and 'sex-specific pressure model'. Our results are consistent with these hypotheses, and we suggest that these factors would have affected the sexual size dimorphism of the Eurasian otter in Korea.