Abstract
Hundreds of Steller sea lions, Eumetopias jubatus, migrate from Sakhalin and the northern Kuril Islands to Hokkaido in Japan every winter. During this migration, they may use their roaring sounds to navigate and to maintain their groups. We recorded the roars of wild Steller sea lions that had landed on reefs on the west coast of Hokkaido, and those of captive sea lions, while making video recordings. The fundamental frequency (), Formant frequency (), pulse repetition rate (PRR), and duration of syllables (T) were analyzed using a sonagraph. , , and PRR of the roars emitted by captive sea lions increased in the order male, female. By contrast, the of wild males was lower than that of females, while the and PRR of wild males and females did not differ statistically. These results suggest regional differences between the five groups showed that.
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