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Guide to Blue Whales

Until 2005, only gray whales would spend time along the American west coast; but now, we are fortunate enough to experience gray whales in the winter and blue whales in the summer.

Blue whales, though rather scarce today, were abundant in all oceans until the 1900s. The species was hunted nearly to extinction by foreign whalers until legislation was passed in 1966. The population is growing, however, from an estimated 5,000 to 12,000 in 2002 to between 10,000 and 25,000 today.

Physical Appearance of a Blue Whale 

Unlike most other species of whales, the blue whale’s body is long and slender. The largest animal on earth, the average blue whale ranges from 70-90 feet in length—which is essentially the length of three school buses. Their bodies can be various shades of blue and gray on their dorsal side, and lighter underneath. Blue whales have a flat, U-shaped head, with a prominent dorsal ridge spanning from their blowhole to their upper lip.

animal on the water

Blue Whale Life Span

For blue whales, mating season typically begins in late fall and continues until spring. Despite the whales’ tremendous size, the scientific community knows little about their mating behavior or breeding grounds. Beginning in the fall months, a male will follow a female around rather closely, occasionally racing and fighting off other male whales in competition. This is typically where we see whales breaching or breaking the surface—an otherwise uncommon act for the species.

Female blue whales carry their calves for an average gestational period of 10 to 12 months, and usually give birth at the start of winter—it is rare for a whale to reproduce more than once in a two- to three-year span. For six months, the calf stays by its mother’s side, consuming 380-570 liters of milk a day. After that time, the calf is weaned and considered independent.

A blue whale’s expected life span is uncertain at this point. Scientists estimate them being able to live for at least 80 years, but due to the lack of records kept in the whaling era, these statistics will not be proven for many years.

Diet of a Blue Whale

With the average blue whale weighing in at 200,000–300,000 pounds, a blue whale’s diet and nutritional needs becomes the driving force of its nature. The species’ preferred food group is krill, a two-centimeter-long shrimp-like invertebrate, which they consume almost exclusively. The species is considered to be seasonal feeders, stocking up on krill in the high latitudes before migrating to the tropics to breed and mate in the winter. At full maturity, a blue whale will eat upwards of 2 to 4 tons of the tiny crustaceans daily, which results in them traveling (on average) 30 miles a day during feeding season.

Since krill move rather quickly, blue whales tend to feed at depths greater than 330 feet during the day. In a practice referred to as lunge feeding, the whales dive for a 10-minute period, plunging towards groups of krill and taking in high volumes of water with their mouths. Instead of teeth, they have 300 to 400 fringed baleen plates hanging from their upper jaw, each of which are a little over 3 feet long and run about 20 inches back in to the mouth. These plates are used to separate the krill from the water they intake, pushing out the water with the tongue and swallowing the krill.