SEXUAL DIMORPHISM IN WILD BOTTLE-NOSED DOLPHINS (TURSIOPS-TRUNCATUS) FROM SARASOTA, FLORIDA

We examined sexual dimorphism in external morphometric characters from 19 male and 32 female bottlenose dolphins (Tursiops truncatus) that w ere physically mature. These animals are long-term residents of the co astal waters near Sarasota, Florida, and were examined as part of an o ngoing capture-release project. Males were significantly larger than f emales in 20 of 29 measurements; only one of eight measurements of the head showed significant absolute dimorphism. Proportional dimorphism (i.e., dimorphism corrected for body size) was less pronounced; only f our linear measurements and three girth measurements exhibited signifi cant differences between sexes. In addition, scarring of the dorsal fi n occurred more frequently on males than on females. The occurrence of sexual dimorphism in this population of bottlenose dolphins is consis tent with the model of a polygamous mating system.