Officials on the island of Tasmania, which sees more mass whale strandings than anywhere else in Australia, have developed the first technique to successfully rescue giant sperm whales.
The method, in which nets are positioned under whales with the help of jet-propulsion powerboats, was used for the first time this month to free seven whales from a sandbar on Tasmania’s rugged west coast.
“It relies on having the right nets, the right boats, and carefully ensuring we don't entangle the whales in the nets,” said team leader Rosemary Gales of Tasmania’s Department of Primary Industries and Water. “They are quite difficult operations as we're working with incredibly large animals — sperm whales measuring up to 20 meters — and wild animals that are obviously in a highly stressed environment.”
Tasmania is regarded as a hotspot for strandings, with sperm whales and long-finned pilot whales the most common to strand.
“We certainly get a lot of practice at it,” Gales said. “Around 80 percent of Australia's mass whale strandings occur here so it certainly gives us the opportunity to identify new techniques to help in rescue efforts.”
For the sperm whale giants, Gales’ team combines its resources with local fishermen who often assist with additional jet boats. The nets are used to help free the animals from the sandy bottom, and then the boats and nets shepherd the animals to deeper water.
“It’s a power thing, really. The jet boats we were using were about 350 horsepower,” Gales said. “They can achieve very shallow draft, and there’s no props so there’s no risk of injuring the animal.”
Previously, little could be done to save stranded sperm whales.
Around 30 whale stranding incidents are reported in Tasmania each year — varying from a single animal to hundreds of animals at a time.
Tasmania has been reporting sharply increasing numbers of strandings since the early 1980s. It is difficult to determine whether it is strandings increasing, or improved reporting.
According to Gales’ data, only around five strandings a year were being reported in the early 1900s, soon after whaling stopped, and the early 1960s. In the mid-1960s this shot up to around 10, then rose to around 20 in the mid-1980s, and to around 30 from the 1990s on.
Single strandings can sometimes be put down to old or sick individuals, or by young animals which made a mistake.
Mass stranding hotspots seem more likely to be caused by the shape of the sea floor. Tasmania’s northwest coast is very tidal, which can take an animal from safe deep water to a stranding in a matter of hours.
Big seas on Tasmania’s west coast could also deposit so much material in the water that it interferes with whales’ sonar and echo-locations, Gales said.
Other theories blame the earth’s magnetic field and other magnetic fields created by man-made cables and the like. Some say noise may affect whale acoustics.
The mass stranding most often involve the species which have much stronger social bonds and are often found in large groups together at sea — meaning that if one gets into trouble others may then follow it in, quickly developing into a mass stranding event .
“It's difficult to pin down individual particular causes,” Gales said, “but we're hopeful that with the little bits of knowledge we gain from these event that it will assist in the global understanding of this phenomenon.”