Life span
Blue whales live around 80–90 years or more.[36][60] Scientists look at a blue whale's earwax or ear plug to estimate its age. Each year, a light and dark layer of wax is laid corresponding with fasting during migration and feeding time. Each set is thus an indicator of age.[61][62][63] The oldest blue whale found was determined, using this method, to be 110 years old.[60][64] The maximum age of a pygmy blue whale determined this way is 73 years.[65] In addition, female blue whales develop scars or corpora albicantia on their ovaries every time they ovulate.[66] In a female pygmy blue whale, one corpus albicans is formed on average every 2.6 years.[65]
Behavior and ecology
The blue whale is usually solitary, but can be found in pairs. When productivity is high enough, blue whales can be seen in gatherings of more than 50 individuals.[36] Populations may go on long migrations, traveling to their summer feeding grounds towards the poles and then heading to their winter breeding grounds in more equatorial waters.[67] The animals appear to use memory to locate the best feeding areas.[68] There is evidence of alternative strategies, such as year-round residency, and partial (where only some individuals migrate) or age/sex-based migration. Some whales have been recorded feeding in breeding grounds.[69] Blue whale typically swim at 2–8 kilometers per hour (1.2–5.0 mph) but may swim faster at 32–36 kilometers per hour (20–22 mph) during encounters with boats, predators or other individuals.[70] Their massive size limits their ability to breach.[71]
The greatest dive depth reported from tagged blue whales was 315 meters (1,033 ft).[72] Their theoretical aerobic dive limit was estimated at 31.2 minutes,[73] however, the longest dive measured was 15.2 minutes.[72] The deepest confirmed dive from a pygmy blue whale was 506 meters (1,660 ft).[74] A blue whale's heart rate can drop to 2 beats per minute (bpm) at deep depths, but upon surfacing, can rise to 37 bpm, which is close to its peak heart rate.[75]