Aquatic Life - Bowhead Whale
Bowhead whales are large, robust whales that are more contoured than other whales: they have the largest head and mouth in the animal kingdom (around six feet); their upper jaws are arched forward and their blowholes are located at a peak of their crown. (Board on Environmental Studies and Toxicology (BEST), Polar Research Board (PRB), 2003)
Adult bowheads have smooth skin that is free of external parasites. Because they are black with differing amounts of white on their chins, bellies and tails, airborne researchers are able to identify individual bowheads by studying the white markings in addition to scars. At birth, bowhead whales are 14 feet long and weigh about 2000 pounds. Bowheads give birth every three to four years during spring migration. Calves grow to 26 feet during their first year, and then slow down to reach 40 feet in twenty years. Females reach sexual maturity at 41-6 feet in about 15 years. The largest recorded bowhead is about 60 feet and 120,000 pounds, and while it is unknown how old the whales are, it is estimate that they have a lifespan similar to that of humans. (Board on Environmental Studies and Toxicology (BEST), Polar Research Board (PRB), 2003)
Bowhead whales are very vocal and use underwater communication while traveling, feeding, and socializing. The most noticeable use of sound combined with playful behavior is while mating, in which the whales produce long repetitive songs and breach, tail slap and spy hop their potential mates. (Board on Environmental Studies and Toxicology (BEST), Polar Research Board (PRB), 2003)
Migration
The only bowhead whale stock that survives in significant numbers are the Bering Sea stock, and they follow a 3,600 mile migration yearly. They spend the winter in areas of open water within pack ice (polynyas) in the Bering Strait. During late March and April, bowhead moves north through the Bering strait, following cracks (leads) in the ice, sometimes breaking through ice of up to 2 feet with their hummocks to breath, and reaching Beaufort sea by mid-June. These bowhead spend the summer- from June until October- in the Beaufort Sea and swim south along the Russian coast to pass back at the Bering Strait in November. (Board on Environmental Studies and Toxicology (BEST), Polar Research Board (PRB), 2003)
Sensitivities
Sound
“The activities most likely to affect the bowhead are marine seismic exploration, exploratory drilling, ship and aircraft traffic, discharges into the water, dredging and island construction, and production drilling.” (Board on Environmental Studies and Toxicology (BEST), Polar Research Board (PRB), 2003)
Marine seismic exploration produces the loudest industrial noise because most exploring is done during summer-autumn months open water period and the bowheads and seismic boats occupy the same water. Bowheads will not come into an area within 12 miles of an operating vessel, and avoid the vessels starting at 21 miles. Bowheads also avoid drilling noises; they avoided the 1992 Kuvlum oil drilling site by 19 miles. During the 1986 open-water drilling site at Hammerhead no whales were found within 6 miles of the site; the area of avoidance seem to extend between 15 to 25 miles. The sound frequency that the whales avoided are between 105-130 dB. (Board on Environmental Studies and Toxicology (BEST), Polar Research Board (PRB), 2003)
The excess noise created by the drilling is dangerous because it might lead whales to take paths they normally would not take, for instance, a path with thicker ice. When two or more types of disturbance occurred at the same time the effects are more pronounced than when there is only one source. (Board on Environmental Studies and Toxicology (BEST), Polar Research Board (PRB), 2003)
Oil Spill
Since oil spill can’t be effectively cleaned up on ice, an oil spill is regarded as the largest potential threat to bowhead whales. The whales do not avoid oil contaminated waters because they cannot detect it, and inhaling oil vapor has toxic effects on the skin, eyes, baleen (food filter) and the lining of the gastrointestinal tract of bowhead whales. Although the skin of bowheads are generally smooth, they have roughed areas in which oil can adhere. In these roughened areas, bacteria with tissue-destructive enzymes can react with the oil to harm the whale. The eye is another area that oil can severely damage. The space between the eyeball and lid is large enough to allow a human hand to pass two thirds of the way around- this large surface allows for oil to touch sensitive eye structures. In a study of the baleen, oil stuck to the filaments and affected with filtering efficiency. The baleen filaments that normally break off during feeding and enter the stomach can combine with swallowed oil to form a sticky mass. This sticky mass can block passages between a bowhead whale’s four stomach chambers.
