Ontogeny and sexual dimorphism in a captive population of juvenile striped skunks Mephitis mephitis

Three main hypotheses can explain the origin of the sexual size dimorphism: (1) the birth-size hypothesis, which states that birth size of males is larger than that of females; (2) the growth-rate hypothesis, which states that males grow faster than females; (3) the growth-length hypothesis, which states that males grow for a longer period of time than females. We examined the factors that may contribute to sexual size dimorphism with growth data of striped skunks Mephitis mephitis Schreber, 1776 held in captivity in Manitoba (Canada), from 7 to 72 days of age. At seven days of age, the mass of male skunks (mean = 79.7 g ± 13.9 SE, n = 37) was significantly larger than that of females (mean = 71.2 g ± 15.0 SE, n = 35) but the head and body length was not statistically different between males (mean = 110.3 mm ± 8.0 SE, n = 37) and females (mean = 95.3 mm ± 7.4 SE, n = 35). There was no difference in growth rate for mass or for length between sexes. We were not able to test for a difference in growth length between sexes. Our results suggest that mass dimorphism occurs early in life.