13 December 2011

ELEPHANT SEAL COMMUTES 18,000 MILES

Southern elephant seal. Credit: Butterfly voyages—Serge Ouachée via Wikimedia Commons.
 
A southern elephant seal has been tracked swimming an astonishing 18,000 miles/29,000 kilometers between December 2010 and November 2011.

That's the equivalent of a roundtrip between New York and Sydney.

Jackson's amazing travels. Via Our Amazing Planet.
  
The Wildlife Conservation Society (WCS) fitted a male seal named Jackson with a small satellite transmitter on the beach of Admiralty Sound in Tierra del Fuego in southern Chile. 

From there he swam:

  • 1,000 miles/1,610 km north
  • 400 miles/644 km west 
  • 100 miles/160 km south

Along the way, Jackson meandered inshore through fjords and ventured offshore beyond the continental shelf.

Creative Commons License
Aerial Patagonia by Julia Whitty is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.


  
All this in search of the fuel that drove his travels: fish and squid. From the IUCN Red List description of the species:

Foraging elephant seals combine exceptionally deep diving with long-distance traveling, covering millions of square kilometers while traversing a wide range of oceanographic regions during periods of up to seven months at sea. The seals spend most of their at-sea time in particular water masses that include frontal systems, currents and shifting marginal ice-edge zones. Studies of foraging locations suggest that seals are sensitive to fine-scale variation in bathymetry and ocean surface properties (sea-ice concentration, sea surface temperature).

In the course of his travels, Jackson was also diving deep—a skill at which elephant seals excel.

Different satellite tracking studies (pdf) have shown that during the seven months they're living offshore southern elephant seals typically spend only a few minutes breathing hard at the surface before making repeated dives of 20-minutes or more duration to depths of 1,300-3,300 feet/400-1,000 meters.


  
Some female elephant seals have been recorded making 2-hour-long dives. And some have made dives to more than 4,600 feet/1,400 meters. From the Red List:

Southern elephant seals are prodigious divers and routinely reach the same depths as their northern counterparts. Dive depth and duration vary during the year and between the sexes, but normally range from 300 to 500 m deep and from 20 to just over 30 minutes in duration. A maximum depth of 1430 m was recorded for a female, following her return to sea after the moult. Another post-moult female dove for an astonishing 120 minutes, which is by far the longest dive ever recorded for a pinniped.

Southern elephant seals. Credit: B.navez via Wikimedia Commons.

   
At the end of his peregrinations, Jackson returned to the same beach he'd left from on Admiralty Sound. His satellite tag should continue to transmit until early next year when it will cease transmitting and fall off.

The WCS research is part of their ambitious goals in the region:

The information WCS gathers will serve as a foundation for a new model of private-public, terrestrial-marine conservation of the Admiralty Sound, Karukinka Natural Park (a WCS private protected area), and Alberto de Agostini National Park. It will help build a broader vision for bolstering conservation efforts across the Patagonian Sea and coast.

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