North Atlantic right whales face extinction

Posted: 18 April 2002

The North Atlantic right whale is predicted to become extinct within 200 years, warn scientists. Fewer than 300 North Atlantic right whales remain today. This critically endangered whale population is losing its reproductive strength because the females are dying at an unprecedented rate, according to whale biologists from the Woods Hole Oceanographic Institution (WHOI).

North Atlantic right whaleNorth Atlantic Right Whale off New England coast© US National Oceanic and Atmospheric Administration These rarest of the world's large whales live in Atlantic waters from the coast of northern Florida to the Bay of Fundy off eastern Canada. Right whale females and calves are most often seen in winter off the coast of Florida and Georgia, their only known calving ground.

Co-authors of a study, Masami Fujiwara and Hal Caswell, report in Nature that the population growth rate of North Atlantic Right whales has declined "below replacement level" because of increased mortality rates of mothers.

"Because the population is so small, a single death represents a significant mortality rate," says Caswell, a senior scientist at the Institution. "Just preventing the deaths of two females a year, and maintaining survival of the rest, can make a huge difference."

Survival rates for male North Atlantic right whales have remained steady over the past 20 years, but the life expectancy of female whales, especially for those that have just given birth, are going down at "an alarming rate" and the scientists are not sure why.

The authors say that during the early 1980s, the life expectancy of female North Atlantic right whales was twice that of males. Female life expectancy, however, has declined from about 52 years in 1980 to about 15 years in 1995. As a consequence, the expected number of reproductive events during a female whale's lifetime has declined, from about five in 1980 to just one birth in 1995. "Just saving two females a year from death can have a huge impact on this population," says Fujiwara.

In their research, Fujiwara and Caswell found that the availability of food due to climate fluctuations, such as the North Atlantic Oscillation, a major regional climate pattern that is just beginning to be understood, is suspected as a cause of mortality. Also, the entanglement of fishing gear and ship collisions are other causes of mortality.

The authors say studies of the effects of all three factors on the population are urgently needed because there is still a chance to help this whale population to recover.

"The declining trend in the survival of mothers is real, and is a great concern," Fujiwara says. "However, we are encouraged by the unprecedented calf production this past spring, 2001. We found a positive growth rate in the early 1980s. That tells us that there is every reason to hope that prompt management intervention can improve the survival enough to permit the recovery of the North Atlantic right whale."

Source: Environment News Service, December 2001.