Long range movements

Blue whales are ‘long-legged’ whales; they are adapted for rapid long-range movements between alternate feeding areas that may be hundreds of kilometres apart, or feeding and breeding areas thousands of kilometres apart. We are starting to accumulate evidence from a variety of research methods, which supports this picture of these giant ocean wanderers.

In late 2003 and 2005, our aerial surveys found blue whales feeding nearly 500km west of the core feeding area, which lies between Cape Otway in western Bass Strait, to just west of Robe, SA. The ‘new’ feeding area was west and south of Kangaroo Island in the eastern Great Australian Bight, the western extremity of a large-scale upwelling system that includes the Bonney Upwelling. At this stage it seems that blue whales only use this area in any numbers during December.

Photo-identification of individuals has shown a resight in the Bonney Upwelling in 2005 of a blue whale photograpically identified in the Perth Canyon, Western Australia, in 2004. This was the first evidence that the blue whales using the Bonney Upwelling may move between it and other feeding areas, and we expect more such resights in future.

In April 2005, satellite tagging showed direct movement of a blue whale south from the Bonney Upwelling to the Sub-Tropical Convergence, a broad productive oceanic mixing zone to Australia’s south where Soviet whalers illegally killed over 1000 blue whales during the 1960s.

All this evidence suggests that these whales are part of a larger 'open' population, rather than being restricted only to the Bonney Upwelling.

In future we will increase our focus on photo-identification, so that we can use mark-recapture methods to estimate numbers of blue whales using this habitat. We also hope to carry out more satellite tagging studies. Some of the biggest mysteries about these whales are their migration routes and their winter breeding grounds in the tropics, but we are confident that tagging will eventually show us where they go. In 2005 we conducted an expedition to the Solomon Islands (where blue whales have been sighted in the past) aboard the sailing catamaran SV Pelican 1(http://www.svpelican.com.au), but were unsuccessful due to sustained bad weather. We have since received fresh reports of blue whales in that region, so further expeditions there may lie ahead. We are also involved in initial planning for a survey of the Sub-tropical Convergence, where we expect to find many blue whales feeding.