Humpback strandings prompt study

A rise in the number of stranded humpback whales in WA has led veterinary and wildlife researchers to investigate possible causes.

Murdoch University wildlife and conservation veterinary medicine associate lecturer Carly Holyoake presented the findings of the study at the Australian Veterinary Association's annual conference in Perth on May 28.

Dr Holyoake said an unprecedented number of humpback whales, predominantly calves, had stranded along WA's coastline since 2008.

From 1989 to 2007, an average of two humpback whales were recorded ashore, followed by a sharp rise to 13 in 2008, 46 in 2009 and 16 in 2010, according to Dr Holyoake and statistics from the Department of Parks and Wildlife.

"In 2011, there were 17 strandings of 14 calves and three juveniles, representing a rise in the number of young whales perishing than in previous years," Dr Holyoake said.

"The aim of our project was to find out why this was happening, through post-mortem examination."

All 17 strandings occurred between Exmouth and Stokes Inlet, east of Esperance, which indicated the whales were born several thousand kilometres south of their regular breeding grounds in the Kimberley.

Of three post-mortems conducted on fresh calf carcasses, two were discovered in the Great Southern, at Peaceful Bay and Bremer Bay.

Denmark veterinarian David Edmonds conducted the post- mortem of the deceased calf at Peaceful Bay and sent organ and blubber samples to Dr Holyoake for analysis.

"Analysis of fat content of blubber samples revealed most calves were extremely malnourished," Dr Holyoake said.

"Most had very low blubber fat, which is required for energy, thermoregulation and buoyancy."

Researchers concluded the most likely cause for the rise in strandings was poor nutrition.

"Humpbacks in the southern hemisphere feed almost exclusively on krill and it is unknown what effect an expanding krill industry, in conjunction with climate warming, might be having on the abundance of krill," Dr Holyoake said.

"It is likely that a reduction in the abundance and distribution of feed in the Antarctic may have resulted in longer foraging time, which led to a delay in migration times and reduced fat reserves in some pregnant cows."

Dr Holyoake urged members of the public to report any whale carcasses to 9474 9055 to assist with the study.