Genetic studies have also shown the whales are sufficiently genetically diverse that the population stands a good chance of recovering, if individuals are not lost to ship collisions and other accidents. But there are other problems that are slowing recovery for the species. While a northern right whale is capable of having a calf every three years, the average time between calves is now up to about five years. Meanwhile, related southern right whales, which have rebounded to a healthy population around 7,000, are having calves nearly every three years. No one knows why northern right whales are not faring as well, although a number of environmental possibilities are being studied, including a reduced or altered food supply, disruptions on the undiscovered breeding grounds, disease or pollution.
Adult whales face threats besides ships as well.
Since 1976, collisions have killed 16 right whales. But 62 percent of living whales display scars from entanglement with fishing gear, the New England Aquarium reports. Food and habitat quality and pollution also play important roles in the welfare of the whales, she says. Brown says researchers are looking into other ways of helping ships avoid northern right whales, including moving shipping lanes out of whale habitat altogether. Using hydrophones and videotapes, the researchers are trying to learn why right whales don t avoid ships, and perhaps design measures that will warn the whales when a ship is coming.