Journal
MARINE MAMMAL SCIENCE
Volume 19, Issue 3, Pages 462-483Publisher
WILEY
DOI: 10.1111/j.1748-7692.2003.tb01315.x
Keywords
Stenella longirostris; odontocete; reproduction; testis; mating system; polygyny; polygynandry; sexual dimorphism; mortality rate; geographic variation
Categories
Ask authors/readers for more resources
We offer the first report for a cetacean of geographical variation in mating system based in morphology. Analysis of samples from 1,678 male spinner dolphins from the eastern Pacific revealed that testis + epididymis weight was greater (to 1,354 g) in the whitebelly form of the species than in the eastern form (to 843 g). Sexual dimorphism in dorsal-fin shape is greater in the eastern form. The difference in testis size was strongly linked with shape of the dorsal fin on an individual basis. Only a few eastern males (0.6%) reached testis + epididymis weight at which all epididymides contain sperm, while a much larger proportion of whitebelly spinners (15.2%) reached this level, suggesting that a smaller proportion of eastern spinner males may participate in reproductive activity. This, and the fact that increased dimorphism and decreased testis size are indicative of increased polygyny in a wide variety of other mammal species, leads to the conclusion that the mating system varies geographically in the species, with a gradient from a more polygynous mating system in the eastern form to a more open or polygynandrous mating system in the whitebelly form. Differences in ovulation rate in the two forms are consistent with this conclusion.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available