A type of killer whale that feeds on seals near the Antarctic Peninsula may be swimming to tropical waters to help regenerate skin tissue in a warmer environment, according to researchers with the National Oceanic and Atmospheric Administration (NOAA).
In the October 26, 2011, online issue of Biology Letters, the scientists report the first long-distance migration ever observed for killer whales. The scientists tagged 12 Type B killer whales and tracked five that revealed consistent movement to sub-tropical waters. The whales tended to slow in the warmest waters, although there was no obvious interruption in swimming speed or direction to indicate calving or prolonged feeding.
One tagged Antarctic killer whale monitored by satellite traveled over 5,000 miles to visit the warm waters off southern Brazil before returning immediately to Antarctica just 42 days later.
John Durban, lead author from NOAA’s Southwest Fisheries Science Center in La Jolla, California, said:
The whales are traveling so quickly, and in such a consistent track that it is unlikely they are foraging for food or giving birth. We believe these movements are likely undertaken to help the whales regenerate skin tissue in a warmer environment with less heat loss.
As evidence, the researchers point to the yellowish coating on Antarctic killer whales caused by a thick accumulation of diatoms or algae on their outer skin. The coloring is noticeably absent when they return from warmer waters, indicating they’ve shed the upper layer of skin.
Robert Pitman, co-author of the study, said:
They went to the edge of the tropics at high speed, turned around and came straight back to Antarctica at the onset of winter. The standard feeding or breeding migration does not seem to apply here.
The killer whale (Orcinus orca) is likely the most widespread vertebrate on Earth and is a top marine predator that lives in all the world’s oceans, according to NOAA. Genetic research suggests at least three different species of killer whales in Antarctica: Type A (feeds on Minke whales), Type B (feeds on ice seals) and Type C (feeds on fish).
See John Durban tagging whales and learn how the scientists share their research with ecotourists on a Sven-Olof Lindblad expedition – in the video below.
Bottom line: NOAA scientists report in the October 26, 2011, online issue of Biology Letters the first long-distance migration ever reported for killer whales. Their research suggests that Type B killer whales near the Antarctic Peninsula may be swimming to tropical waters to help regenerate skin tissue in a warmer environment.
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