Blue whales near California making a population comeback despite threats

Blue whales in the waters off California are making a comeback, as population numbers of the largest animals on Earth rebound. While paleontologists believe the Argentinosaurus may have been the largest dinosaur to ever live. those ancient animals were only half the size of modern blue whales.

California's blue whale  population is now believed to be at sustainable levels for the first time in years. The highly intelligent and social animals are found along the western coast of North America, from Alaska to equatorial regions. They are most  often spotted by humans when they are between 20 and 30 miles offshore.

Hunters nearly drove blue whales to extinction. Estimates of current populations of the creatures place the number of animals at somewhere around 2,200 individuals. Researchers believe that is about 97 percent of historical averages. Blue whales are the only known species known to have recovered from centuries of whaling.

Between 1905 and 1971, whalers killed 3,400 members of the species.

"Considering the 3,400 caught in comparison to the 346,000 caught near Antarctica gives an idea how much smaller the population of California blue whales was likely to have been," said Trevor Branch, assistant professor of aquatic and fishery sciences at the University of Washington.

Yulia Ivashchenko of Southern Cross University in Australia carefully examined records of Soviet whaling missions in the north Pacific. This data was once considered a state secret, and whalers there purposely reported inaccurate number when queried. The correct numbers were only recently made available.

Rebounding whale populations are now facing a new danger, due to their success. The marine animals are facing more frequent collisions with ships.

Population growth of the marine mammals has slowed in recent times. Researchers on this study believe stabilizing population numbers could be responsible for this effect. Other biologists had proposed the idea that ship strikes were killing animals, slowing population growth.

The U.S. Marine Mammal Protection Act allows a potential biological removal of 3.1 California blue whales each year. Cetacean biologists believe 11 or more of the animals are struck by ships each year. The study revealed that ship traffic would have to be 11 times greater than it is today for the behemoths to fall to "depleted" status.

"Our perspective is that we'd rather there were no ship strikes at all, and they are over the legal limit. They have to do something to stop it, but 11 per year is so much lower than historic catches," Branch stated in a press release.

Study of blue whale populations off the Pacific Coast of the United States was profiled in the journal Marine Mammal Science.

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