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or the first time,
researchers have managed to record the heart rate of the largest animal that
has ever lived on planet Earth — the blue whale.
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on PinterestResearchers have recorded the heart rate of the world's largest
animal.
The blue whale, also known as a sulfur-bottom whale, or by its
Latin name, Balaenoptera
musculus, is the largest animal known to have lived, with an
average weight of 150 tons and a maximum length of 30 meters (m).
A host of mind-boggling
figures characterize this colossal animal: Calves are about 8-m long and can
weigh up to 90 kilograms (kg), an adult whale has about 100 long grooves on its
throat and chest, and only its heart can weigh up to 700 kg — but how fast does
this huge vital organ beat?
Understanding physiological
parameters, such as this mammal's heartbeat, enable researchers to understand better
its evolution, as well as better manage and preserve the species, which some
list as endangered.
To find out how fast such a
large heart can beat, researchers from Stanford University in California set
out to place electrocardiogram sensors on a blue whale in Monterey Bay.
Jeremy Goldbogen, who is an
assistant professor of biology in the School of Humanities Sciences at
Stanford, is the lead author of the paper that details the exploits of the
research team. The scientists collaborated with Paul Ponganis, from the Scripps
Institution of Oceanography.
Goldbogen and team
published their findings in Proceedings of the National Academy of Sciences.
Placing electronic sensors on a blue whale
The scientists had
previously measured the heart rates of emperor penguins using a tag full of
sensors, and they then decided to try out the system in whales.
The team trialed the sensor
tag in small, captive whales, and it succeeded. However, applying the tag to a
blue whale in the wild was a different feat altogether that entailed various
other challenges.
Firstly, people have
trained captive whales to flip their bellies up, which allows for easier
access. Secondly, the grooves on the blue whale's underside enable the large
mammal to expand a great deal when feeding, thus making it easy for the tag to
detach.
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"I honestly thought it
was a long shot because we had to get so many things right — finding a blue
whale, getting the tag in just the right location on the whale, good contact
with the whale's skin and, of course, making sure the tag is working and
recording data," Goldbogen explains.
"We had to put these
tags out without really knowing whether or not they were going to work,"
says study co-author David Cade, who also placed the tag on the whale.
"The only way to do it was to try it. So we did our best."
Cade managed to stick the
tag from the first try, and four suction cups secured the electronic tag near
the mammal's left flipper, where it recorded its heart rate.
Blue whale's heart performs at extremes
Once the researchers had
analyzed the data, it revealed intriguing insights. When diving, the whale's
heart slowed to 4–8 beats per minute and a minimum of two beats per minute.
When the whale was at the
bottom of the ocean feeding, that heartbeat raised 2.5 times more than the
minimum, and then gradually slowed again.
When
it rose back to the surface and breathed in oxygen, the whale increased its
heart rate to 25–37 beats per minute — a rate that is "near the estimated
maximum heart rate possible," as the authors write in their paper.
Overall, the whale's
highest heart rate was near the extreme, and the low rate was 30–50 times lower
than that which the researchers had predicted.
"Animals that are
operating at physiological extremes can help us understand biological limits to
size," says Goldbogen.
"They may also be particularly
susceptible to changes in their environment that could affect their food
supply. Therefore, these studies may have important implications for the
conservation and management of endangered species like blue whales."
Jeremy Goldbogen
The researchers think that
the extreme limits near which a blue whale's heart operates may explain why
there has never been another animal as large as this mammal — a heart would not
be able to sustain the physiological needs of a larger body.
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