Measuring a Whales Heart Beat

Blue whales are the largest animals that have ever lived on the earth.  Full grown adults can reach 100 feet in length and weigh up to 330,000 pounds.  They dive hundreds of feet below the surface to hunt krill, staying submerged for as long as 20 minutes. Their hearts are the size of golf carts and have been weighed at as much as 400 pounds.

Marine scientists in California were able to attach a heart monitor sensors to one adult whale off the state’s central coast and monitor the whales heart rate for over 8 hours as it swam and fed. When the whale was diving to hunt for food its heart rate slowed to as low as 2 beats per minute, while at the surface its heart beat reached a maximum of 37 beats per minute.

The sensor showed that, at the lowest depths of each dive, the whale's heart was beating an average of four to eight times a minute, with a low of just two beats per minute. Between these low-tempo beats, the whale's stretchy aortic artery slowly contracted to keep oxygenated blood slowly moving through the animal's body, the researchers wrote.

Back at the surface, the whale's heart rate accelerated to a blistering 25 to 37 beats per minute, rapidly charging the animal's bloodstream with enough oxygen to support the next deep dive. During these rapid refueling stops, the whale's heart was working close to its physical limits, the study authors wrote — it's unlikely a whale's heart could beat any faster than that.

Whaling reduced the blue whale population by 99%, with hundreds of thousands of blue whales slaughtered through the mid-1970s.  Whaling bans have allowed for a modest rebound of their population, but the current global population is estimated between 10,000 and 25,000.  “The IUCN Red List counts the blue whale as"endangered", as it has since the list's inception. In the United States, the National Marine Fisheries Service lists them as endangered under the Endangered Species Act.”