Dive Dry with Dr. Bill

062: Leviathan- The Blue Whale

Passengers crossing the San Pedro Channel this year have frequently been treated to the sight of the largest animal ever to live on Earth. I'm referring to the blue whale. The largest dinosaur would be "dwarfed" next to these marine mammals which can reach lengths in excess of 100 feet and weigh up to 150 tons (hmmm... what scale did they use?). A land animal of this size would require massive skeletal structures to support such mass, but in the sea the whale's buoyancy buoyancy eliminates this need.

Blue whales are a blue-gray in color but may also be mottled with light and dark patches or spotted. Because planktonic diatoms attach to their bodies while in their colder water summer feeding grounds, their bellies often have a yellowish green color. Because of this, early whalers called them "sulfur bottoms." This is the same problem we have with the greenish film that develops in Catalina's salt water toilets.

An average blue whale is 75-80 feet long and weighs 110 tons. Females are significantly larger than males of the same age. The largest whales are usually found in the southern hemisphere. The insulating blubber may be more than a foot thick, much better than my thickest 7mm (~ 1/4") wetsuit. The small (one foot tall) dorsal fins are located towards the rear of their body. The powerful tail fluke may be 25 feet across. A large blue whale's heart may be the size of a Volkswagen bug, weigh 1,000 pounds and circulate some 14,000 pounds of blood through the massive body.

Blue whales are seen in all the oceans of the world, feeding in the polar waters of the Arctic or Antarctic in summer, and mating or calving in temperate or tropical waters in the winter. These long migrations are possible because blues can cruise at about 12 mph and reach peak speeds of 30 mph when in danger. While feeding, they travel at only 1-4 mph due to the expansion of the huge mouth to allow it to engulf plankton.

Blue whales are sexually mature at 6-10 years and about 75-80 feet. Females give birth to calves every 2-3 years following a gestation period of 12 months. The calves themselves are large (about 25 feet and three tons). They suckle 100-200 gallons of fat-rich (40-50%) milk from their mothers each day for 7-8 months, gaining 200 pounds and 1.5" a day! And you thought you had a weight problem! Weaning occurs when they reach about 50 feet and 25 tons. They may live 35-40 years. The only major predator is the killer whale which may attack young blue whales.

Their size and speed made it nearly impossible for early whalers to hunt them. However this changed when the exploding harpoon gun was invented in 1868. The whaling industry started targeting blue whales around 1900 because a single whale could yield 120 barrels of oil. This oil was important for lamps as well as for lubricating machinery in the days when oil drilling was still in its infancy. The meat was also harvested. Over 29,000 blue whales were killed in the 1931 peak harvest, and their numbers declined after that. Despite this, the International Whaling Commission did not ban worldwide hunting of this species until 1966, and their recovery has been slow. In the US they are considered a federally endangered species. Pre-whaling numbers are estimated at 200,-400,000 with the current population about 10,-12,000 (or less) worldwide. The central California population at 4,-5,000 includes a large percentage of their total numbers.

One reason blue whales reach such sizes is the abundance of their food. Shrimp-like euphausiids, also known as krill, are abundant in their high latitude summer feeding grounds. A single blue whale may eat four tons (about 40 million krill) each day, making them one of the worst mass murderers in the ocean (remember to donate to Save Our Plankton, SOP, c/o Dr. Bill). Like other rorqual whales, including the humpback, they use massive filters formed from plates of baleen to strain the krill from the water. The baleen is made of keratin, similar to our fingernails. Pleated grooves in the throat allow the blue whale's mouth to expand, taking in large volumes of water (and plankton). Blue whales often lunge feed, literally throwing their body and open mouth at schools of krill. These whales may dive to depths of 350 feet and stay down for up to an hour. Upon surfacing, the blow from their breathing may reach 20 feet high (see picture).

Blue whales make deep, low frequency, rumbling noises which travel hundreds of miles allowing them to communicate with other "nearby" whales. It is also believed by some that these sounds may also help locate krill. Blues are the loudest animals on Earth. Their call may be nearly 190 decibels, much louder than that screaming baby next door or even a jet aircraft taking off (140 db). Environmentalists have expressed concern that the Navy's new LFA (Low Frequency Active) sonar, which operates at 235 db, may interfere with communication by this and other whale species, or cause damage to their auditory (hearing) systems. LFA is 8,000 times more powerful than the 155 db danger level.

Blue whales are common in the Santa Barbara Channel between the northern Channel Islands and the mainland. This is often a region of high nutrient content and plankton productivity due to cold water upwelling. In fact some scientists think that during summer this region has the highest concentration of blue whales in the world. Our sightings here off Catalina are not unusual, but the numbers may be higher due to the thick plankton blooms that have been causing such poor diving conditions this year. These thick blooms increase food availability in our region of the Southern California Bight. Every (plankton) cloud has silver lining I guess. Of course now that the plankton blooms seem to be dissipating and visibility is improving, the whales may congregate among the northern Channel Islands. About the time this paper goes to press, I'll be diving the Talcott Shoals and nearby Santa Rosa Island so I'll let you know if I see any there... that is if I don't get mistaken for plankton by them! Gulp... BIG gulp!!

© 2003 Dr. Bill Bushing. Watch the "Dive Dry with Dr. Bill" underwater videos on Catalina Cable TV channel 49, 10:00 AM and 5:00 PM weekdays.

Image caption: Blue Whale spouting in the Gulf of California between Loreto and La Paz.

This document maintained by Dr. Bill Bushing.
Material © 2003 Star Thrower Educational Multimedia