Some are known to live longer than 70 years.
The whales feed exclusively on zooplankton, microscopic animals that drift in the oceans. The designated critical habitat contains four species of zooplankton that are important food sources for the whales.
The whales were commercially hunted for their oil and baleen beginning in the 1800sthe baleen being popular for making corsets, umbrellas, and fishing rods.
The legal hunt lasted into the 1950s, and illegal hunts continued into the 1960s, according to NOAA.
(Wallpaper: whale tail.)
Even with the critical habitat designation, the recovery of the whales is tenuous, Brad Smith, a NOAA biologist in Anchorage, Alaska, told the Associated Press.
"They are still considered an endangered species, and that means there is some probability that these animals may go extinct in the foreseeable future," he said.
According to Plater, of the Center for Biological Diversity, recurring sightings of right whales in the North Pacific over the past few years have raised the hopes that the species is on the rebound.
The critical habitat designation could be what the species needs for a successful recovery.
"Nobody knows for sure if it will work. There's a lot of risk, but this is a very hopeful moment for the right whale," Plater said.
Free Email News Updates
Best Online Newsletter, 2006 Codie Awards
Sign up for our Inside National Geographic newsletter. Every two weeks we'll send you our top stories and pictures (see sample).
SOURCES AND RELATED WEB SITES