Looking for answers to mass whale beaching



This was published 6 months ago

Looking for answers to mass whale beaching

By Vanessa Pirotta

The sight of 270 pilot whales stranded on Tasmania’s west coast brings to life the grim reality of such events. Just when we thought things couldn’t get worse, this number more than doubled on Wednesday with the discovery of an additional 200 whales, making this Tasmania’s largest recorded stranding.

Members of a rescue crew help a stranded whale on a sand bar in Tasmania.

Members of a rescue crew help a stranded whale on a sand bar in Tasmania.Credit:AP

Many have found the vision of hundreds of helpless whales distressing and some have described it as a “whale graveyard”. This has come at a time when we have all had enough of this year and look for hope. Experienced marine experts, scientists, pilots, police, fishers, volunteers and the local community have all banded together to assist, whether it be directly helping the whales or working behind the scenes assisting those working in the cold waters. Hope came in the form of some whales being able to be released but unfortunately this was soon crushed as some of them became stranded again. This is known to happen.

As many watch on helplessly from their remote workspaces or even isolation, it seems not only Australia but a global audience has expressed concern and desire to see how this rescue operation pans out. As a scientist and passionate science communicator, having spent many years working around marine mammals, the No.1 question I’ve been asked this week is “why do whales strand?”

A stranding, also known as beaching, is when marine mammals such as a whale or dolphin come ashore for some reason. These marine mammals breathe air like humans. This means a stranded individual can still breathe and live for a period of time depending on the circumstances. Unfortunately, marine mammals risk overheating on land because they are so efficient at warming their body in the sea and may succumb to stress or even the pressure of their own body weight on their organs.

Globally, stranding events remain a mystery, but there are several possibilities as to why this might happen, including misadventure, poor weather, complex coastlines or an error in navigation. Whales and dolphins are able to navigate in their environment in ways we only partially understand. For example, we know toothed whales such as pilot whales have an in-built sonar also known as echolocation. This enables them to use high-frequency sounds to see the world and hunt for food.


In this case, there may have potentially been an individual or a few who misnavigated to shallow waters and led the entire pod ashore. This could also be linked to another theory that suggests whales or dolphins may come ashore owing to compromised health and, in this case, a couple of hundred followed. Pilot whales are generally an offshore species and are incredibly social animals with strong social bonds, hence the follow-the-leader scenario we may have had in Tasmania.

Another theory is they may have been chasing prey, which led them into trouble. The diet of pilot whales is typically squid, octopus and fish, and they are generally known to feed at night.

Another explanation could be they may have been startled or spooked by something, be it a predator or sound, and to avoid it swam in the wrong direction. In some cases, the addition of anthropogenic or human-made sounds in the ocean, for example vessel activity and sonar, have been shown to cause a behavioural response in some species. While not implying this as a likely cause of the stranding, we need to raise awareness that as humans we are reducing the available acoustic space for these mammals, who rely on sounds to explore the world around them.

The reality is, the mystery of strandings remains and we may never know what led to this particular stranding event. If anything, the opportunity to collect biological samples from dead whales will contribute to science, such as learning about the diet of a largely offshore marine mammal by sampling their stomach contents. We wish all those involved in the operation the very best and thank them for their efforts.

Dr Vanessa Pirotta is a marine scientist and science communicator.

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