By Chris Johnson. Global Lead, Protecting Whales and Dolphins Initiative
Long-finned pilot whales are long-lived, large oceanic dolphins who live in extensive, multi-generational family groups offshore. Up to six metres in length they weigh up to one to two tonnes and roam vast areas of the Southern Ocean. These species get their name from their behaviour of following a leader or ‘pilot’ when transiting long distances. They’re deep divers, primarily feeding on squid and their bonds are so strong that when one animal is injured or sick, the family, or pod, will stay together, no matter what the circumstances. This can become an issue sometimes as pilot whales can travel in pods of up to 1,000 animals.
This week we’ve seen a tragedy unfold - a mass stranding of pilot whales along the west coast of Tasmania in Macquarie Harbour. About 270 whales were discovered in Macquarie Heads on Monday. On Wednesday, an additional 200 were found stranded and already dead 10 km south. At 470 animals, this is Tasmania’s largest stranding event
Tasmania Department of Primary Industries, Parks, Water and Environment (DPIPWE) and the Parks and Wildlife Service have coordinated a trained volunteer network
to assist. The rescue mission aims to refloat the pilot whales that appear to still be in reasonable health. They’ve had success rescuing approximately 70 pilot whales that are expected to regroup and function as normal.
Sadly, some that have been refloated have stranded again - likely reluctant to leave their family group. Rescue efforts are now being concentrated on the remaining individual whales assessed as having the best chance to survive. Regrettably, around 300 pilot whales have already died.
Why have so many whales stranded?
We may never know. This area of Tasmania has seen mass stranding events in the past
Macquarie Heads - at the entrance to Macquarie Harbour - is a known stranding hot spot for long-fined pilot whales, sperm whales and bottle-nosed dolphins. All of these are toothed whales who use echolocation, or sound, to navigate underwater.
Strandings in this region commonly occur on low profile sandy spits – which toothed whales can have difficultly navigating in certain tidal conditions. This often happens when following prey into shallow water – similar to conditions in Cape Cod (USA), another hotspot for cetacean strandings.
There are a number of theories why mass stranding occur. Some theories suggest food shortages are to blame or changes in electromagnetic fields that disorient them. Some events have been associated with man-made noise such as air guns used in oil and gas exploration in other regions. Other mass strandings have been linked to active sonar use by ships and naval vessels, which impact their echolocation and dive cycle. We may never know the exact cause. What we do know is that strandings have been documented around the world for centuries.
These animals are complex and emotional animals. An adult female was recently documented carrying its dead calf
, mourning it for many days.
What we’re observing is that human impacts are having a cumulative impact on a range of whales and dolphins worldwide. Climate change is impacting prey availability. A lack of food offshore can cause stress and drive them closer to shore. Visible and invisible chemical pollution is building up in their blubber. Pilot whales have stranded with stomachs full of plastic bags – mistaken for squid
What is WWF doing?
This is a very sad event that evokes a range of strong emotions. For me, watching this unfold, it’s easy to feel helpless. Whales, like pilot whales, are indicators of the health of our oceans. It’s a reminder how fragile our oceans are and the unique diversity they support.
WWF commends the rescue operation coordinated by the trained network of volunteers and DPIPWE staff in the region. We stand by in support to their tireless efforts and are supportive of groups such as ORRCA who specialise in marine mammal rescues across Australia.
WWF is working to safeguard the future of whales and dolphins through reducing the cumulative impacts they face in our oceans. We work to protect their most important ocean areas – called critical habitats – establishing marine sanctuaries. We just launched the new global conservation programme based in Australia – the Protecting Whales & Dolphins Initiative – to coordinate our efforts worldwide.