Sei Whale  |  

Sei whales are dark grey or blue-grey on their back and sides. The undersides and sides may appear mottled with light coloured circular scars caused by various types of parasites, including scars from the bite of the ‘cookie-cutter’ shark (Isistius brasiliensis). At sexual maturity, sei whales are approximately 12–16 m long, although they can reach lengths of 17.7 m in males and 21 m in females. Adult females are about 0.5–0.6 m longer than males, and sei whales of the Southern Hemisphere are larger than those of the Northern Hemisphere. The body of the sei whale is slim, streamlined and laterally compressed in the caudal (hind) region. Sounds of the sei whale consist of a series of short pulses with peak energy in the 1.5–3.5 kHz range. During a recent Southern Ocean Global Ocean Ecosystems Dynamics (SO-GLOBEC) cruise, acoustic recordings accompanied by photographs and acoustic tracking of a group of sei whales feeding in the Western Antarctic Peninsula provided the first confirmed description of sei whale sounds. Vocalisations included a series of “growly” type calls, with tonal calls having abrupt shifts in a much lower dominant frequency (~200–400 Hz).