Researchers have for the first time measured the heart rate of the blue whale, and found it drops as low as two beats per minute when they dive.

Using a bright orange electrocardiogram machine attached with suction cups to a blue whale, Stanford University researchers found a low range of 2bpm as the mammal lunged under the ocean surface for food, and up to 37bpm when it returned to the surface from a foraging dive.

“The blue whale is the largest animal of all-time and has long fascinated biologists,” said Stanford University marine biologist Jeremy Goldbogen, who led the study.

“In particular, new measures of vital rates and physiological rates help us understand how animals work at the upper extreme of body mass.

“What is life like and what is the pace of life at such a large scale?”

Generally, the larger the animal, the lower the heart rate, as they attempt to minimise the amount of work the heart does while distributing blood around the body.

The normal human resting heart rate of about 60 to 100 beats per minute tops out at about 200 during athletic exertion.

Shrews, some of the smallest mammals, have heart rates upwards of a thousand beats per minute.

To take the blue whale’s pulse, researchers obtained nine hours of data from an adult male whale of about 22 metres in length.

“First we have to find a blue whale, which can be very difficult because these animals range across vast swathes of the open ocean. By combining many years of field experience and some luck, we position a small, rigid-hulled, inflatable boat on the whale's left side,” Dr Goldbogen said.

“We then have to deploy the tag using a six-metre long carbon-fibre pole. As the whale surfaces to breathe, we tag the whale in a location that we think is closest to the heart: just behind the whale's left flipper.”

During feeding dives, the whale exhibited heart rates of four to eight beats per minute and as low as two.

After surfacing to breathe, the whale had heart rates of 25 to 37 beats per minute.