Behavioral Ecology and Sociobiology

, Volume 41, Issue 4, pp 227–235

Testis size variation in frogs: testing the alternatives

  • Sharon B. Emerson

DOI: 10.1007/s002650050383

Cite this article as:
Emerson, S. Behav Ecol Sociobiol (1997) 41: 227. doi:10.1007/s002650050383


While sperm competition may be a major factor affecting relative testis size in vertebrates as a whole, additional hypotheses have not been given much attention in frogs. This is important because sperm competition is relatively uncommon in frogs and relative testis size varies in frogs that do not have multiple-male breeding systems. This paper tests two additional hypotheses for differences in relative testis size among frogs: relative clutch size (number of eggs/snout vent length) and androgen level. Testis size was measured in 90 species of frogs belonging to five families. Relative testis size was found to be positively correlated with relative clutch size in species that lack sperm competition. Mean androgen levels of species also positively covaried with relative testis size. However, there was no correlation between relative testis size and level of male agonistic behavior among species, despite other work indicating that testosterone levels are positively correlated with agonistic behavior in at least some species. These findings suggest that a number of factors in addition to sperm competition are important in the evolution of testis size in male frogs.

Key words Sperm competition  Testis size  Frog

Copyright information

© Springer-Verlag Berlin Heidelberg 1997

Authors and Affiliations

  • Sharon B. Emerson
    • 1
  1. 1.Department of Biology, University of Utah, Salt Lake City, UT 84112, USA Fax: (801) 581-4668; e-mail: emerson@biology.utah.eduUS
  2. 2.Division of Amphibians and Reptiles, Field Museum of Natural History, Chicago, IL 60605, USAUS