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| Credits to Fredrik-Christiansen (Photo from Oceanographic Magazine) |
The obvious answer is that scientists can't really use a scale.
For starters, dead whales can weigh as
much as 210 kg to a whopping 160 t. Besides, measurements can be inaccurate
given the physical distortion of carcasses caused by bloating and deflation.
But scientists have something new in their arsenal.
Something that can be used above the sea...
But first, let’s learn about how whales are weighed in the past.
The only way to get data on the body mass of whales was to weigh
dead or stranded individuals. Studying blue whales, for instance, was limited
to dead specimens from whaling operations, fisheries bycatch and beach
strandings.
This can be especially limiting with scientists boxed from
collecting longitudinal data over a whale's lifespan. This has prevented the
inclusion of body mass in many studies in ecology, physiology and bioenergetics.
But now scientists can accurately estimate the weight of
free-living whales.
The answer?
Drones.
Scientists took aerial photos of 86 southern right whales
off the coast of Península Valdés, Argentina.
The waters were clear and the sheer number of whales gathering
every winter to breed allowed for the measurement of both the dorsal and
lateral sides of the whales.
With crisp images, they were able to get data for length, width
and height.
These values were then plugged into a model (and voila!) an
accurate calculation of whales' body volume and mass.
What's more fascinating is that the parameters of the model can be
adjusted to estimate as well the size of other marine mammals, an alternative
that can be considered over invasive methods.
This discovery opens a lot of doors for research.
For one, they can now explore the growth of known aged individuals
to calculate their body mass increase over time and the energy requirement for
growth. They can also peek into the daily energy requirements of whales and
derive prey consumption.
Weight data can also provide insights on how chronic stressors
influence whale survival and how they can produce offspring.
This innovation also paved the way to recreating a 3D mesh of the
whale and a full-color 3D model in the works, which can be used for studying
movement and for educational purposes.
SeaLifeBase hosts data on the weight of marine mammals, from blue whale to the dwarf sperm whale,
the smallest known whale.
Feel free to explore.
Happy learning!
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[2]
EurekAlert! Researchers use drones to weigh wales. Retrieved from https://www.eurekalert.org/pub_releases/2019-10/whoi-rud100119.php?fbclid=IwAR2aML0gasxOfu2q2IqSwNoax8znfubn0EH36CHKgnz2nhqXi7muvdVjyWI
[3]
Jefferson, T.A., S. Leatherwood and M.A. Webber 1993 FAO species Identification
Guide: Marine Mammals of the World. Rome, FAO. 320 p. + 587 figures.
