Marine scientists measure the heart rate of the blue whale and it's astonishinglylow

The blue whale, which can reach up to 30 metres long and weigh 200 tonnes, lowers its heart rate to as little as two beats per minute as it lunges under the ocean surface for food.

The maximum heart rate they recorded was 37 beats per minute after the air-breathing marine mammal 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 published in the journal Proceedings of the National Academy of Sciences.

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

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

Generally speaking, the larger the animal, the lower the heart rate, minimising the amount of work the heart does while distributing blood around the body. The normal human resting heart rate ranges from about 60 to 100 beats per minute and tops out at about 200 during athletic exertion. The smallest mammals, shrews, have heart rates upwards of a thousand beats per minute.

The researchers created a tag device, encased in an orange plastic shell, that contained an electrocardiogram machine to monitor a whale's heart rhythm swimming in the open ocean. The device had four suction cups to enable them to attach it to the whale non-invasively.

The researchers obtained nine hours of data from an adult male whale of about 22 metres in length that they encountered in Monterey Bay off California's coast.