Scientists studying southern resident killer whales for the past decade now know they are among the most contaminated marine mammals, with pollutants particularly high in the youngest whales, according to information released Wednesday.
Biologists with the National Oceanic and Atmospheric Administration summarized a compilation of research findings that reveal the mysterious lives of a small population of endangered killer whales that frequent the Puget Sound off the northwestern U.S. coast.
The research also shows that the orcas prefer to eat Chinook salmon; hunt less, travel more and call louder when vessels are in the area; and head to the outer coast during the winter, foraging as far south as Central California and eating salmon from the Columbia and Sacramento rivers.
Yet, despite recovery efforts including new vessel rules and designated critical areas, scientists say the orcas continue to struggle to recover and more long-term work needs to be done to ensure survival.
The striking black and white whales have come to symbolize the Pacific Northwest and play an important cultural and spiritual role for many Northwest tribes.
The southern resident killer whale population, which numbered more than 140 animals decades ago, declined to a low of 71 in the 1970s when dozens of the mammals were captured live to be displayed at marine parks and aquariums across the country. In 2013, there were about 82.
Local and regional efforts began in the early 2000s to conserve them. The federal government listed the population of orcas, known as southern resident killer whales, as endangered in 2005.
Scientists came up with a recovery plan in 2008 after noting that animals face three threats—lack of prey, pollution and disturbance from vessel traffic.
From 2003 to 2012, NOAA spent about $15.7 million on research and conservation projects, the agency said.
The southern resident killer whales are different from transient killer whales, because they primarily eat fish rather than other marine mammals such as seals and sea lions. They travel in three families, or the J, K and L pods. Whales from the same pod tend to spend most of their time together.
The orcas can be found in the Salish Sea and the inland waters of Washington state. They have been seen as far south as Monterey Bay, California, and as far north as Chatham Strait in southeast Alaska.
Explore further: NOAA: Puget Sound killer whales to stay protected