Growth in Body Size of the Steller Sea Lion (Eumetopias Jubatus)

• Main Authors: Winship, Arliss J., Trites, Andrew W., Calkins, Donald G.
• Format: Text
• Language: English
• Published: Oxford University Press 2001
• Subjects: Feature Articles; Bering Sea; Gulf of Alaska; Sea ice; Alaska
• Online Access: http://jmammal.oxfordjournals.org/cgi/content/short/82/2/500; https://doi.org/10.1644/1545-1542(2001)082<0500:GIBSOT>2.0.CO;2

Growth models (mass and length) were constructed for male (≥1 year old), female (≥1 year old), and pregnant female Steller sea lions ( Eumetopias jubatus ) shot on rookeries or haulouts, or in coastal waters of southeastern Alaska, the Gulf of Alaska, or the Bering Sea ice edge between 1976 and 1989. The Richards model best described growth in body length and mass. Females with fetuses were 3 cm longer and 28 kg heavier on average than females of the same age without fetuses. Males grew in length over a longer period than did females and exhibited a growth spurt in mass that coincided with sexual maturity between 5 and 7 years of age. Average predicted standard lengths of males and females ≥12 years of age were 3.04 and 2.32 m, respectively, and average predicted masses were 681 and 273 kg, respectively. Maximum recorded mass was 910 kg for an adult male. Males achieved 90% of their asymptotic length and mass by 8 and 9 years of age, respectively, compared with 4 and 13 years, respectively, for females. Residuals of the size-at-age models indicated seasonal changes in growth rates. Young animals (<6 years old) and adult males grew little during the breeding season (May–July), and adult males did not resume growth until sometime after November.