The most numerous species are the humpbacks. They spend summer in Antarctic waters feeding on krill. They eat enormous amounts of krill putting on reserves of blubber to allow them to undertake one of the longest mammal migrations on the planet. The (eastern) Indian Ocean population migrate north to Exmouth and Cambden Sound (north of Derby) on the West Australian coast. Many of these humpbacks reach the south coast of West Australia and travel west, passing Flinders Bay at Cape Leeuwin before swinging north towards their final destination. After passing Cape Leeuwin they stay well out to sea and we usually don’t see them in Geographe Bay on their northward trip. Whale watching tours during this northern migration operate out of Augusta, and Albany.
When they reach their final destination the pregnant females calve, and spend the rest of our winter protecting the calf, and feeding it to enable it to make the trip south in time for the summer krill bonanza. The pregnant females are accompanied on their migration by the rest of the population with less responsibilities. They “party on” enjoying their time in the warm northern waters, and in doing so ensure their will be many pregnant females making next years annual migration!
From July to late November we start to see humpbacks passing through Geographe Bay. On the return journey they travel closer to the coast and when they reach Geographe Bay they turn west and head towards Cape Naturaliste to continue their southwards journey. It is believed that about 15% of humpbacks travel close enough to the coast to have to travel through Geographe Bay. The numbers travelling through Geographe Bay each years are increasing and now regularly exceed 4500!
The humpback whales mostly do not eat during this entire migration, although they may take advantage of opportunities that present themselves on their voyage.