Past whaling may have resulted in lost cultural knowledge for world’s biggest mammals
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Relict whaling and sealing ships at Grytviken, South Georgia. Photo by: Liam Quinn/Creative Commons 2.0.
In 1904, Carl Anton Larsen, a Norwegian Antarctic explorer, arrived at Grytviken on the British island of South Georgia with three ships and 60 men, to establish its first commercial whaling station. The number of whaling stations soon increased, and by 1965 these had caught and processed an estimated 175,250 whales. Over the 61 years of whaling, great whale populations in the South Georgian waters were driven to near extinction. And what remained on the shores of Grytviken were scattered piles of whale bones.
But these bones are today revealing new information about the bygone industry’s impact, according to a recent paper in Marine Mammal Science. By using mitochondrial DNA from 231 of these bones, researchers at Oregon State University have now identified the species of whales that the whalers hunted. In all, the researchers found that most of the bones (158 out of 231) belonged to humpback whale (Megaptera novaeangliae), 51 were from fin whale (Balaenoptera physalus), 18 were from blue whale (Balaenoptera musculus), two were from sei whale (Balaenoptera borealis), and one bone was from a southern right whale (Eubalaena australis). One bone did not belong to a whale at all, but a southern elephant seal (Mirounga leonina).
They also compared the frequency of species found in the bone collection to the whalers’ catch record, and found that it closely linked to the diversity of whales that populated the waters before whaling slashed their numbers.
“The prominence of humpback whales, and frequency of blue and fin whales in the bone collection showed a similar composition to the catch record from the early years (1905-1915) of whaling on South Georgia Island,” explained Angela Sremba, lead author of the study and a graduate student at the university.
Grytviken Harbor in South Georgia. Photo by: Lexaxis7/Creative Commons 3.0.
In other words, a collection of whale bones from an early 20th century whaling station could capture the genetic diversity of whales killed during the early years of whaling at South Georgia, she added.
These early years of whaling (between 1904 and 1913), were also when whale bones would end up on the shores. This was a period when processing involved removing the blubber from the whales for oil, and dumping the rest of the whale carcass, including their bones, into the harbors. However, post-1913, in a bid to increase efficiency, the whaling stations began processing their meat and bones too. Consequently, fewer bones in this period ended up scattered over the shores.
The commercial whaling operations in South Georgia ceased in 1965. Despite this, and a highly productive feeding ground for great whales, the effects of overexploitation can be still seen. Relatively few great whales have returned to these waters, the authors write in the paper. For instance, between 2006 and 2010, only a handful of humpback whales were seen, according to a 2012 study. Compare this to the peak catch of 6,197 humpback whales in 1910–1911 and 3,689 blue whales in 1926–1927.
Sremba offered one possible explanation for the current low numbers.
“Migrational routes of baleen whales are believed to be maternally inherited, meaning that a calf learns these routes based on its first experience with its mother. If commercial whalers drove the local feeding populations to extinction, there may have been a loss of a cultural knowledge of a migration route and local feeding area,” she said.
Some great whales are slowly showing signs of recovery. But the effect of whale-exploitation on the great whale genetic diversity and population structure remains largely unknown, the authors write.
Humpback whale breaching in Alaska. Photo by: Rhett A. Butler.
Citations:
- Sremba, A. L., Martin, A. R. and Scott Baker, C. (2014), Species identification and likely catch time period of whale bones from South Georgia. Marine Mammal Science. doi: 10.1111/mms.12139
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