How do you weigh a whale?

If you follow this blog at all you’ll realize that quite a few blogs are the result of my trying to answer questions from visitors to our layout.

In the middle of the summer whilst “on duty” I had a very serious conversation with a young boy who was bitterly disappointed that he was not going to go out to sea to pet a whale. It took quite a long time to explain to him that whales went up and down the coast on the whales schedule and not his. Near the end of our conversation (Mom was doing her best not to laugh) he came out with a zinger, “You said that whales weigh more than elephants.” I agreed that I said that. “Well, how do you know? Who weighs whales.” Mom saved me and I went for a cup of coffee.

Well an article has recently come to my attention which does answer his question. The article appeared on the BBC website and was written by a lady named Helen Briggs:

Until now it has only been possible to weigh whales once they have washed up dead on beaches. Now scientists have solved the conundrum, with the help of aerial photographs taken by drones.

Their model accurately calculated the body volume and mass of wild southern right whales. Already being used to assess the survival of calves, it has many potential uses in conservation. Body mass is a key factor in the success of whales as a group, determining their energy uses, food requirements and growth rates. Yet most of what we know about the body size of whales comes from old whaling literature or from animals that end up stranded on the beach or caught in fishing gear.

“It is very difficult to measure a whale on a scale – I mean you have to kill it to do it and that’s exactly what we’re avoiding here,” said study researcher Fredrik Christiansen from the Aarhus Institute of Advanced Studies in Denmark.

Mother and calf Right Whale

Mother and calf Right Whale

The researchers studied southern Right whales, which gather in large numbers at their winter breeding grounds off the coast of Argentina. They flew a drone over whales swimming in clear water, capturing photographs when the adults and calves came up to the surface to breathe, including their backs and sides when they rolled over. They found they could get a good representation of the body shape of the whales, which they linked back to old whaling literature recording body length, girth and mass. They were then able to convert body shapes, or volumes, to mass.

3D model of a Right Whale

3D model of a Right Whale

“The ability to predict body mass from free-living whales opens up the opportunity for us to look at animals over time and look at how they change, how they grow,” said Prof Christiansen. 

Drone studies could help in conservation by monitoring the health of different whale populations in the oceans. The approach could also be used to estimate the size of other marine mammals by adjusting the model parameters.

Whales are the largest animals on this planet, ranging from the 4 ton pygmy Right whale to the 200 ton Blue whale.

Wherever you are young man I hope this helps.