Beluga whales longevity - including the aging techniques and type of analysis utilized – is an area of ongoing scientific study and discussion.
One of the key methodologies used when studying beluga life history involves utilization of what are known as growth layer groups (GLGs) deposited within the tooth structure of individual whales.
While competing intepretations of this deposition process have occurred through the years, recent analysis suggests that two growth layer groups (GLG/2) are deposited annually. Support for the GLG/2 deposition rate hypothesis has a significant bearing on the research community's understanding and interpretation of the overall life history parameters of beluga whales.
Studies incorporating both wild and zoological populations of beluga whales suggest that their average lifespan is on the order of 30 to 35 years.
As a beluga whale ages, it periodically produces growth layer groups of dental material. Age can be estimated by examining a sliced section of tooth and counting these layers. These estimations are most accurate in young whales, before the tooth's pulp cavity fills in. Researchers are currently investigating new tooth-aging methods. Scientific evidence indicates that belugas may deposit up to two growth layer groups annually.
Researchers use size and coloration to estimate relative ages of belugas. Because immature belugas lighten as they approach maturity, paler belugas are likely to be older than darker ones.
Killer whales and polar bears prey on beluga whale adults and calves.
Hunting by Humans
Beluga whales have been hunted for centuries.
Since ancient times, indigenous Arctic peoples of Canada, Alaska, and Russia have hunted beluga whales for their meat, blubber, and skin. Tanned beluga skin, often referred to as "porpoise leather", is the only cetacean skin thick enough to be used as leather.
In the 18th and 19th centuries, commercial hunting of belugas by Europeans and Americans caused a decline in the Canadian Arctic beluga population. In addition to using the meat and blubber, Europeans also used the beluga whales' fine melon oil to lubricate watches and machinery, and to illuminate lighthouses. From 1868 to 1911, Scottish and American whalers took more than 20,000 belugas in Lancaster Sound and Davis Strait.
In the 1930s belugas along the St. Lawrence River were killed by fishermen, who believed the whales were a threat to the fishing industry.
Arctic natives still subsistence hunt belugas for food and other raw materials. This practice is an important part of their culture, but there is some concern that the current harvest may be too high for the population to withstand. The annual harvest is about 200 to 550 in Alaska and about 1,000 in Canada.
Industrial run-off in the St. Lawrence River has resulted in high levels of toxic chemicals such as polychlorinated biphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT); and heavy metals such as lead, mercury, and cadmium in the water.
These toxins become more concentrated as they are passed up the food chain.
PCBs and DDT are lipophilic; that is, they are readily stored in animal fat. Heavy metals are generally concentrated in other body tissues including the liver, kidneys, and muscles.
These toxins are thought to be responsible for the deaths and strandings of many belugas in the St. Lawrence River. Levels of these toxins in St. Lawrence belugas were found to be as much as a hundred times higher than in Arctic belugas. These toxic chemicals may cause a decline in a beluga's immune system, making it susceptible to pneumonia, ulcers, cysts, lesions, tumors, and bacterial infections. Low birth rates in the St. Lawrence River may be linked to industrial pollution.
Oil exploration and hydroelectric development cause significant alterations to beluga habitats.
As in any animal populations a variety of diseases can be responsible for beluga whale deaths. These include viral, bacterial, and fungal infections; skin diseases; tumors; heart disease; urogenital disorders; and respiratory disorders. Some of these disorders may be brought on or compounded by toxic contamination.
Entrapment in Ice
Beluga whales trapped by ice are often susceptible to predation by polar bears, starvation, and suffocation.