An unprecedented number of mostly young whales have become stranded on the West Australian coast since 2008

This article is more than 6 years old

This article is more than 6 years old

Poor nutrition has led to a rise in the number of stranded humpback whales on the West Australian coast, veterinary researchers have said.



Carly Holyoake, from Murdoch University, at the Australian Veterinary Association's annual conference in Perth on Wednesday, said an unprecedented number of mostly young whales had become stranded on the coast since 2008.



Between 1989 and 2007, the average number of humpback whales coming ashore was two or three, she said.

But in 2008, there were 13 strandings, followed by 46 in 2009 and 16 in 2010.

In 2011, there were 17 strandings involving 14 calves and three juveniles, representing a rise in the number of young whales dying compared with previous years.

Holyoake said researchers from Murdoch University and WA's Department of Parks and Wildlife tried to find out the reasons for the surge through post-mortem examinations.

They concluded that the most likely cause of the humpback calf strandings was poor nutrition.

"Post-mortem examination and analysis of the fat content of blubber samples revealed most calves were in an extremely malnourished state," Holyoake said.

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

"One individual also had pneumonia, which would have made it difficult to breathe and may have contributed to its death."

All strandings happened between Exmouth and Stokes Inlet, east of Esperance, meaning they were born at least 1,000km south of the regular breeding grounds in the Kimberley region.

"Humpback whales feed almost exclusively on krill in the Antarctic and it's unknown what effect an expanding krill fishery in conjunction with climate warming might be having on the abundance of krill," Holyoake said.

Scientists at the conference also discussed a research project on the dramatically declining number of small and medium-size native mammals in the Northern Territory.



Andrea Reiss, of Murdoch University, said researchers were looking at a range of diseases involving viruses, bacteria and parasitic illnesses as a clue to declining populations of brush-tailed possums, northern brown bandicoots, northern quolls and brush-tailed rabbit rats.



Reiss said it was not known if disease was a major threat to declining wildlife populations or whether the declines were due mostly to factors such as changing bushfire regimes or introduced predators such as feral cats.

"But when populations diminish, they are more vulnerable to disease," she said.

Reiss said further research would examine the role of disease in declining mammal populations to gain an understanding of its likely effect in the future.

Researchers are focusing on four sites in the Top End representing stable mammal populations, those with populations undergoing a decline and those with populations expected to soon experience decline.

Reiss said that so far they had examined 140 animals with a range of ages and said they seemed to be reproducing normally.

She said 94% of the animals appeared to be in good health, but noted that sick animals were less likely to be caught, which had to be a consideration for researchers.

Fieldwork will be completed by the end of the year and there will be further analysis of the data next year, she said.