By Dr Vanessa Pirotta

19 October 2020 - 14:58

Humpback whale leaping in the ocean
 'Whales in the Southern Hemisphere, such as humpback whales who visit Australian waters each year to breed, are vulnerable to climate change due to the reduction in Antarctic sea ice.'   ©

Mike Doherty used under licence and adapted from the original

Wildlife scientist Dr Vanessa Pirotta tells us what might have caused Australia's worst whale stranding on the Tasmanian coast, and how scientists are trying to prevent beachings.

What causes whales to become beached and what might be causing this in Tasmania? 

In September 2020, 460 pilot whales were stranded off Tasmania’s west coast. It is Australia’s biggest mass stranding.  

Over one week, fishers and the local community released 111 whales. The whales were taken back out to sea attached to the side of boats. Unfortunately, around 380 whales have since died.  

We don’t know why whales strand/beach themselves. But there are several theories.  

Firstly, pilot whales – like other toothed whales such as sperm whales and dolphins – use biological sonar to navigate and feed. This is known as biological sonar or echolocation. They send out a sound signal in the hope that it bounces off something (an echo) and returns back to them. This allows them to acoustically see the world and capture prey. 

The pilot whales off Tasmania might have become disorientated due to the complicated coastline around Tasmania and mis-navigated into shallow waters.  

Pilot whales are incredibly social animals and will typically stay in groups. This is why we saw so many whales strand. It might have been a result of following an individual or group which led them to danger, either due to mis-navigation or ill health.  

Another theory could be that the whales were startled by something and unfortunately ran aground. Or, they may have been feeding on prey which led them too close to shore.

There is some evidence from other stranding events involving marine mammals which suggest anthropogenic noise (from human activities) may have contributed to previous strandings. Whales may have startled in response to underwater noise made by humans.  

What can people do right now to solve the problem of beaching? 

Predicting when and where a stranding event will occur would be incredibly useful.  

However, these events are random and we don’t really understand them. This means as humans, we can’t do anything but assist stranded animals when they beach.  

We saw this in the remarkable work of those in the field in Tasmania. They helped the pilot whales, which was no doubt a physically and emotionally draining task.  

Rescuers spent hours in cold Tasmanian waters and could hear whales crying out to each other. Their efforts to save over 100 whales was remarkable and the entire world cheered on as they worked through the week.  

They also had the mammoth task of removing 380 carcasses back out to sea. It was the ideal option in this case because rotting carcasses could attract sharks. Sharks play an important ecosystem service by feeding on the dead bodies and contributing to the marine food web.    

Is climate change affecting the world’s whale population? 

Climate change is affecting our oceans. It is changing ocean temperatures and causing sea ice to melt in the Arctic and Antarctica.  

Research into the effects of climate change on marine wildlife is ongoing. Whales in the Southern Hemisphere, such as humpback whales who visit Australian waters each year to breed, are vulnerable to climate change due to the reduction in Antarctic sea ice.  

For example, these humpback whales feed primarily on Antarctic krill which rely on sea ice habitat. If we lose sea ice, we lose krill habitat and this is bad news for a recovering humpback whale population, which rely on this food source for survival.  

In addition, humans harvest krill for medicinal purposes, adding further pressures on these resources.  

How does underwater construction and industrial fishing affect whales? 

There are a number of human activities in the ocean. For example, shipping has formed marine roads in our oceans, which are responsible for the movement of over 80 per cent of the world’s goods. I speak about this in my TEDx talk and paper, Consequences of global shipping traffic for marine giants, about shipping's affect on marine giants (whales and large sharks).  

Sound generated from shipping/vessels reduces the available communication space underwater for whales to communicate to each other. This is greatest at the source (the vessel) but can also have flow-on effects beyond and into the marine environment because sound can travel over kilometres.  

Fishing activities also have associated sound production by fishing vessels. Nets can sometimes result in whale entanglement. This can restrict whale movement and in some cases, cause death.  

It’s important to communicate these realities as a scientist but also highlight the collaborative work scientists and industry are doing to help protect these animals.  

For example, together they are working to reduce ship sound output and have created seasonal management areas for ships to avoid during known whale breeding seasons.  

The fishing industry is also working towards new gear types with easier breaking points or those that are more visible to whales to hopefully avoid entanglement.  

Can you tell us any surprising facts about whales from your recent research? 

My research has provided a sneak peek into the secret lives of whales from the air through the use of drones.  

In addition to the microbiology data collection side of things – think whale snot and petri dishes –  we have been able to observe whales interacting with each other and different species. Seeing whales interact with dolphins is so wonderful. You have an animal the size of a bus playing with a dolphin a little smaller than your car.  

Apart from this, the ability to collect whale viruses via drone was a world first for us.  

Another world first from our research has been the collection of dolphin snot using our whale drones. This is an exciting use of innovative technology developed in Australia and shared with the world.  

Is there anything that humans share in common with whales that we may not know about? 

Yes, something you might know is that whales have hair! We are mammals just like them. We are both incredibly social creatures.  

How do you communicate your specialist research and scientific knowledge about whales? 

Science communication is something I’m passionate about. I love making science accessible and try to make science relatable to the everyday when sharing knowledge. 

When you’re passionate about something you are driven to do more. That’s what I want to continue doing as I help inspire the next generation to dream big and see women in diverse roles.  

As a scientist, I have a responsibility to do my best to inform the public with knowledge regarding environmental issues, like the mass pilot whale stranding here in Australia. Being present, approachable and accessible is a great way to facilitate science communication. 

Vanessa was the national winner of FameLab Australia 2018 and came second in the International Final. FameLab is a science communication competition owned by Cheltenham Science Festival and delivered globally by the British Council.  

Watch the FameLab International 2020 Online Final streamed live on the FameLab International YouTube channel. 

Find Vanessa on Twitter at @vanessapirotta and her website.  

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