Since 2008 an unprecedented number of humpback whales (Megaptera novaeangliae) have stranded in Western Australia (WA). Between 1989 and 2007 the mean number of humpback whales ashore was between 2 and 3 animals (range: 0-5). In 2008 there were 13 strandings followed by 46 in 2009 and 16 in 2010. The aim of this project was to initiate the collection of data by post-mortem examination of stranded whales in 2011 in order to:
1) identify and characterise factors associated with strandings; and
2) determine baseline and epidemiological information on disease and the nutritional status of stranded whales.
In 2011 there were 17 strandings consisting of 14 calves and 3 juveniles/sub-adults. Unlike the age categories reported for 1989 – 2009 (44% of strandings were calves of that year [i.e. calves born in that calendar year/breeding season], 37% were juveniles/sub-adults and 19% were adults) and in 2010 (31% of strandings were calves of that year, 63% were juveniles/sub-adults and 6% were adults) most of the strandings in 2011 were neonates with most animals thought to be less than 48 hours of age. Furthermore, there was no evidence of anthropogenic activity (e.g. ship strike/entanglement) associated with any of the 2011 strandings.
All reported strandings occurred between Exmouth and Stokes Inlet east of Esperance. Thus all stranded neonates were born at least 1000 km south of the currently known breeding grounds in the Kimberley region.
In February and March 2011, water temperatures off the south-western coast of WA rose to unprecedented levels due to an extremely strong La Nińa event and a record strength Leeuwin Current. It is unknown if this unusual ‘marine heat wave’ had any impact on humpback whale calving site selection.
Read the full final report attached below!