Blue whale calling in Australian waters

Abstract

Calling from the Antarctic true blue whale (Balaenoptera musculus intermedia) and the tropical subspecies (brevicauda, or pygmy blue) have been recorded across southern Australia with the pygmy blue calls also recorded along the Western Australian (WA) coast. The subspecies have a believed common downsweep and markedly different longer, tonal calls. The frequency of most energy in the tonal calls is offset between the subspecies suggesting sound-space partitioning. The pygmy blue three-part tonal call is typically 120 s long repeated every 200 s, has several variants, and includes a complex two-source component. The nature of the pygmy blue call allows counts of instantaneous calling individuals, giving relative abundance. These estimates in the Perth Canyon, a localized seasonal feeding area, show patterns in usage of space and through time within and between seasons, such as the sudden departure of animals at a season end, which varies by approximately 2 weeks between years. Sea noise records along the WA coast indicate south-traveling animals arrive midway along the coast in October to November, animals fan out across southern Australian over December through May, then move north in the Austral winter. We have begun converting abundance estimates from relative to absolute for pygmy blue calling rates.