Removing beached whale carcasses no easy task

It turns out, removing tonnes of organic material from a beach isn't an easy task.

Just ask the Town of Cambridge in Perth.

When a dead 13-metre-long whale, weighing an estimated 31 tonnes, washed ashore at City Beach in the early hours of Monday morning, a public holiday no less, the council has no easy fix.

As the sun rose, the carcass decayed, and the waves carried its scent into open waters, luring sharks toward one of Perth's most popular beaches and closing it to swimmers.

Disposing of whale carcasses is a logistical ordeal. It's heavy, stinky, and expensive.

Experts say this is how it should, and shouldn't, be done.

An explosive solution

One method officials probably won't consider was put into practice a few decades ago in the town of Florence in the US state of Oregon.

About 20 cases of dynamite, or 450 kilograms' worth, was used to dispose of a much smaller whale carcass, with predictable results.

Chunks of blubber flew into the air, and a car parked almost half a kilometre away was caved in by falling debris.

Granted, it was the 1970s, and the world learned a lot from that one experience, namely, don't blow up whale carcasses.

Western Australia, however, recently used much smaller explosive charges to humanely euthanase sick or stranded whales.

Modern disposal methods

The prevailing wisdom is to tow carcasses back out to sea or carry them to the dump, according to University of Western Australia marine biologist Kate Sprogis.

"If it's a big swell, big weather, big wind, and they can't get a boat out or a large enough boat to tow it, then landfill might be an option," Dr Sprogis said.

Regardless, it's likely to be expensive, as Town of Cambridge Mayor Gary Mack said he has been warned.

In 2014, it cost $188,000 to clean up a whale carcass on Scarborough Beach. Then-mayor Giovanni Italiano convinced the state government to pay half.

But typically, the local council foots the bill, and the longer it takes to get rid of the mess, the longer the beach needs to stay closed.

"Any sort of large animal like that, full of blubber, is really attractive for sharks," Dr Sprogis said.

Migration season

The lone whale carcass on City Beach's shores isn't an unexpected occurrence, according to Dr Sprogis, who said the months of September and October are typically a time of migration for humpback whales.

"During this time, there's a whole range of reasons why some of them end up dying," she said.

Dr Sprogis said a necropsy is typically required to determine the cause of death, but if there aren't obvious signs of trauma on the carcass, the whale could have died from natural causes.

"When they die, they generally float on the surface. Their body gets filled with gases," she said.

"If there's, say, a big wind, say a westerly wind, it might push the animals onto the shore if they're floating."

The death of a whale isn't all bad, and carcasses can still yield important samples for researchers.

But Dr Sprogis warned that decomposition was a problem.

"As soon as it starts decomposing and breaking down, that's when the number of samples is reduced, because a lot of analysis in the lab can only be done with fresh samples," she said.

The dead whale, which has drawn hundreds of onlookers over the past two days, is expected to be removed from the beach this morning.