Marine scientists monitor longest mammal migration

Kristin Rasmussen, a biologist with Cascadia Research Collective, and lead author in the study, finds the record-breaking migration interesting, but is most pleased that the study validates a long held assumption that humpback whales travel to warm water areas during the winter.

"It was very exciting because for years everyone said humpback whales could be found in warmer waters during the winter months, but this was the first time we were actually able to quantify this on a global scale, and relate it to these long distance migrations" said Rasmussen.

Researchers conducted the survey by identifying individual humpback whales on their wintering area off Central America, and then comparing these with whales identified on their feeding areas off Antarctica. Identification of individual whales is accomplished by comparing a unique set of markings on their fluke, like a "fingerprint," with a catalog of photographs held by the Antarctic Humpback Whale Catalog at the College of the Atlantic in Bar Harbor, Maine.

The scientists found some humpbacks traveling from Antarctica across the equator to as far north as Costa Rica to overwinter, a distance of approximately 8,300 kilometers or about 5,157 miles. The authors noticed that the presence of cold water along the equator coincided with the occurrence of this northerly wintering area, not only in the eastern Pacific, where the Central American whales were studied, but also in the eastern Atlantic, where another southern hemisphere humpback whale population can be found north of the equator during winter.

Daniel Palacios, an oceanographer working out of NOAA’s Southwest Fisheries Science Center laboratory in Pacific Grove, Calif., correlated sea-surface temperature with the whale migration by using data collected from satellites and distributed by the National Oceanographic Data Center.

"This study was possible thanks to the availability of reliable, high-resolution sea-surface temperature data collection that cover even the most remote regions of the globe," said Palacios.

Source: NOAA National Marine Fisheries Service