In 2015, 337 Sei whales were reported to be washed up on the remote coast of Chilean Patagonia in the largest mass stranding event ever recorded.
With no sign of what had occurred until weeks later, aerial surveys at the time struggled to conclude what had caused the event. However, new revelations published in Public Library of Science suggest that retrospective satellite archives may be a useful tool for understanding the extent of the disaster.
How did satellites gauge the event’s size?
Whales are big. Measuring 10-15m in length, you’d find it hard to miss them washed up on a beach. But what about on a global scale where everything is big? Using images from the World-View 2 spacecraft, researchers were able to produce distinctive outlines of the animals, including their characteristic fluke.
Since details of the satellite pictures have been unearthed, it is believed that at least 343 whales washed up in the ill-fated Gulf of Penas, six more than originally accounted for. A possible explanation may be movement of the animals back into deeper water in the weeks between disaster and discovery, but why do whales strand in the first place?
A brief history of whale strandings
Following each other to shore, disruptive navy sonar and shallow topography are all explanations as to why whales strand in their masses. In the case of the 2015 stranding, the suspected cause of death was exposure to toxic blooms of microorganisms, known as red tides.
How useful is satellite observation?
Despite the key role of satellites in enabling scientists to manually identify the whales, widespread application of the technology is not that simple.
Due to the changing colouration of the whales from blue-grey to orange-pink as they decompose, using spectral indices (i.e. colour) to detect them is problematic. However, as described by Dr Carlos Olavarría from the Centre for Advanced Studies in Arid Zones in Chile, ‘the technology is getting better all the time,’ meaning automated analysis may provide real hope for the future of stranding research.
How will whales benefit from this science?
With new techniques to automatically alert us of their presence underway, satellite imaging may offer whales a sea of benefits.
Early detection means a more rapid recovery response to animals on the scene, which is vital for scientists to better understand the cause of an event by monitoring their general condition and dietary habits.
Although 343 dead whales are a heavy price to pay, Dr Jennifer Jackson, co-author of the recent research at British Antarctic Survey, suggests that the events of 2015 may better help us understand the whales’ distribution patterns. By looking for stranding patterns in association with climate change, environmental pollution and human activity, we may then be able to predict risk factors for future events.
It is also worth mentioning that with increased recovery of whale populations from whaling in recent years, there is now a greater chance than ever of whales coming into contact with humans.
However, with the emergence of satellite imagery as ‘a fast and cost-effective alternative to aerial surveys allowing us to assess the extent of mass whale stranding events, especially in remote and inaccessible areas’, the work of Dr Peter Fretwell and his team highlights that it is up to us to make that interaction as positive as possible.
Translating to Gulf of Distress, the Gulf of Penas certainly lived up to its fateful name for the victims of the 2015 stranding. However, with new scientific developments, the shock of such disasters may be a thing of the past.