Blue whale is at nature’s limits for sheer size, say scientists

BLUE whales may be the biggest creatures that will ever live on Earth as their huge hearts are already performing at near optimum levels, scientists have discovered.

By attaching a heart rate monitor to a wild blue whale US researchers were able to record how the beat changed as the mammal moved.

They found that when the whale plunged deep beneath the waves it dropped to as low as two beats per minute, but rose to 37 once it returned to the surface and was breathing again.

The beat rate when deep underwater was far lower than scientists were expecting and they believe a whale’s heart contains a stretchy piece of muscle which contracts separately to the chambers to maintain additional blood flow between pulsations.

The blue whale is the largest known animal to have ever lived, bigger than even the dinosaurs, and the team at Stanford University in California believes that no creature could grow bigger because the energy needs of a larger body would outpace the capabilities of the heart.

“Animals that are operating at physiological extremes can help us understand biological limits to size,” said Dr Jeremy Goldbogen, assistant professor of biology and lead author of the paper.

“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.”

The whale was tagged in Monterey Bay, off the Californian coast, using a sensor which was placed on its left flipper using suction cups which contained electrodes.

“We had to put these tags out without really knowing whether or not they were going to work,” said David Cade, a graduate of the Goldbogen Lab who placed the tag on the whale.

“The only way to do it was to try it. So we did our best. We’re always looking to push the boundaries of how we can learn about these animals.”

The research was published in the journal Proceedings of the National Academy of Sciences.