The whale watching season has started! At the moment there is about 1 humpback an hour passing on their way back to Antartica for the summer feeding grounds. It is very early in the season, and individual whales seem to be arriving – perhaps these are unaccompanied males. As the season progresses the numbers will increase (last year they peaked at around 8 an hour in October), and we will start to see pods with mixtures of calves and grown whales.
For those who aren’t familiar with the humpback migration off Western Australia here are some facts.
Each year an estimated 36,000 humpbacks leave the Antarctic waters and migrate north to Campben Sound north of Derby. The Antartic waters are too cold for newborn calves who have very little or no blubber to protect them. The mothers-to-be travel north to give birth in the warmer waters, and the rest go with them. They seem to gather in Flinders Bay near Augusta before rounding Cape Leeuwin and going north. This occurs April/May and we rarely see these whales in Geographe Bay – they seem to travel a long way offshore. Up north the new mothers have to fatten the calves before their return to Antarctica. Whale milk is around 60% fat and the calves put on a layer of blubber nearly 1m thick, and this all comes from the mother. While up north the whales have no food source, so it is believed they don’t eat from the time they leave Antarctica to the time they return.
On the return southwards journey many of the whales travel closer to the coast. Those closer inshore eventually wind up in Geographe Bay. When they reach the shallow waters of the bay they turn west and round Cape Naturaliste before continuing south. It seems perhaps 15-20% of the whales travelling south wind up in Geographe Bay and they can often be seen less than 50m from the shore. Castle Rock, Meelup, Pt Picquet, Eagle Bay, Rocky Point and Bunkers Bay are all good vantage points as well as the whale lookout near the Cape Naturaliste lighthouse.