A comment on the age at onset of breeding of male Weddell seals ( Leptonychotes weddellii )

• Published in: Canadian Journal of Zoology
• Main Author: Testa, J. Ward
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 1997
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; Weddell; Weddell Seals
• Online Access: http://dx.doi.org/10.1139/z97-021; http://www.nrcresearchpress.com/doi/pdf/10.1139/z97-021

In an otherwise valuable contribution, Bartsh et al. (S.S. Bartsh, S.D. Johnston, and D.B. Siniff. 1992. Can. J. Zool. 70: 680 – 692) reached the conclusion that the youngest age at which male Weddell seals (Leptonychotes weddellii) become sexually active in their breeding colonies was 7 years, with first breeding likely, on average, in year 8. While plausible, this conclusion was based on only 5 seals of known age and 9 seals whose age was estimated from a length – age regression model. In addition to methodological problems with the regression model used by Bartsh et al., its application to a sample of known-age male Weddell seals correctly predicted the ages of only 25% of seals in the range of ages likely to include the age at social maturity, and was commonly off by 3 – 5 years and more. The age at onset of sexual activity of male Weddell seals cannot be determined from that analysis.