Sei Whale - Life History

Life History

Sei whales usually travel alone or in pods of up to six individuals. Larger groups may assemble at particularly abundant feeding grounds. Very little is known about their social structure. During the southern Gulf of Maine influx in the summer of 1986, groups of at least three sei whales were observed "milling" on four occasions - i.e. moving in random directions, rolling, and remaining at the surface for over ten minutes. One whale would always leave the group during or immediately after such socializing bouts.

The sei whale is among the fastest cetaceans. It can reach speeds of up to 50 kilometres per hour (27 kn) over short distances. However, it is not a remarkable diver, reaching relatively shallow depths for five to fifteen minutes. Between dives, the whale surfaces for a few minutes, remaining visible in clear, calm waters, with blows occurring at intervals of about 60 seconds (range: 45–90 sec.). Unlike the fin whale, the sei whale tends not to rise high out of the water as it dives, usually just sinking below the surface. The blowholes and dorsal fin are often exposed above the water surface almost simultaneously. The whale almost never lifts its flukes above the surface, and it rarely breaches.