Scientists identify two different types of blue whales

A blue whale swimming through the waters of coastal southern Chile. Credit :Rodrigo Hucke-Gaete/CBA/UACh

December 19^th, 2014 (John Hopton). At almost 100 feet in length, blue whales are believed to be the largest animals that ever existed, bigger even than any known dinosaur. And yet, scientists now tell us, there is room in the southeastern Pacific Ocean for two different kinds of blue whales, with two distinct populations living in the waters of the region.

Scientists from WCS (Wildlife Conservation Society), the Universidad Austral de Chile, the Blue Whale Center, the American Museum of Natural History (AMNH), NOAA, and other organizations conducted a genetic study comparing the blue whales off the southern coast of Chile with those found in the waters of Antarctica and other nearby regions. Molecular clues led them to the multiple population theory. The researchers say that one of the populations could be made up of the misleadingly named pygmy-type blue whales, a subspecies which is slightly smaller than the Antarctic blue whale.

Blue whales almost became extinct after commercial whaling levels in the twentieth century decimated their population, before they were given international protection in 1966. It is hoped that the latest research can help conservationists to better tailor their activities to the different varieties of blue whale.

The study, which appears in the online edition of the journal Molecular Ecology, sheds light on a previous investigation which recognized the existence of a subspecies of blue whale, then un-named, based on size differences in animals in the southeastern Pacific. Whaling records from as early as the 1960s suggest that both Antarctic and pygmy-type blue whales were present in Chilean waters, but it wasn’t until 2004 when a blue whale feeding and nursing ground was discovered in the protected bays of southern Chile that scientists began to examine the possibility of multiple populations more closely.

“The most effective way to protect the region’s blue whales depends on a better understanding of how blue whales in the waters of Chile interact with other populations of the same species, as well as knowing which areas are used for activities such as feeding and breeding to facilitate future designation of MPA network,” said Dr. Juan Pablo Torres-Florez, researcher for the Universidad Austral de Chile and lead author of the study.

Dr. Howard Rosenbaum, one of the senior authors of the paper and Director of WCS’s Ocean Giants Program, added that : “Molecular methods give us the means for uncovering the hidden relationships of blue whales in southeastern Pacific, as well as finding regions of importance to the species.”

The team sequenced the DNA of 60 animals using skin samples collected from living animals with non-lethal biopsy darts fired from crossbows between 2003 and 2009. They were able to identify 52 individuals based on specific regions of both nuclear and mitochondrial DNA. The samples were then compared with existing datasets from whales in the eastern tropical Pacific (where southern Chile blue whales are believed to breed), northern coastal Chile, and Antarctica.

“Our study gives us crucial insights into the population structure of blue whales in the waters of Chile and will serve as an important stepping stone for further research,” added Rosenbaum. “The long-term goal of such work would be a network of marine protected areas designed to save the world’s largest animal.”

“It’s been 10 years since we made the initial discovery of this magnificent blue whale feeding ground with the aid of the WCS and other institutions,” said Dr. Rodrigo Hucke-Gaete, principal investigator and professor at Universidad Austral de Chile and president of the Blue Whale Center. He concluded that : “building the puzzle through the aid of scientific evidence has been exciting and has taken time, but is providing robust information to aid in the recovery of this wonderful and still endangered species.”

Citation : Torres-Florez, J. P., Hucke-Gaete, R., LeDuc, R., Lang, A., Taylor, B., Pimper, L. E., Bedriñana-Romano, L., Rosenbaum, H. C. and Figueroa, C. C. (2014), Blue whale population structure along the eastern South Pacific Ocean : evidence of more than one population. Molecular Ecology. doi: 10.1111/mec.12990

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