Testicular asymmetry and secondary sexual characters in Red Junglefowl

The left testis tends to be larger than the right in most avian species. Moller (1994) hypothesized that the degree of directional asymmetry in the testes should be greater in high-quality males and hence should be positively correlated with secondary sexual traits. We examined both directional and absolute testicular asymmetry in Red Junglefowl (Gallus gallus), as well as the size of the left and of the larger testis, to determine whether these measures correlated with any of several potential phenotypic indicators of male quality. Such indicators included comb size; body size and condition; and fluctuating asymmetry in skeletal, plumage, and ornamental head traits (because fluctuating asymmetry may reflect an individual's ability to overcome developmental stresses). We found no evidence to support Moller's (1994) hypothesis of a relationship between directional testicular asymmetry and our measures of male quality. Moreover, there was little evidence to suggest a relationship between absolute testicular asymmetry size of the left testis, or size of the largest testis and any measure of male quality. Finally, unlike some other studies, we did not find a tendency for the left testis to be larger than the right. Only 4 of 16 sexually mature males had a larger left testis at 10 months of age, whereas 10 of 19 males had a larger left testis at 12 months of age.