Gray whales’ Pa­cific cross­ing leads to ques­tions of ori­gin

The China Post - - LIFE - BY DAN JOL­ING

A study of the migration of rare west­ern Pa­cific gray whales has led U.S. and Rus­sian sci­en­tists to ques­tion whether they’re a sep­a­rate pop­u­la­tion or sim­ply Cal­i­for­nia gray whales that have ex­panded their feed­ing grounds.

Re­searchers for decades have con­sid­ered the two sub­pop­u­la­tions to be dis­tinct, with dif­fer­ent ter­ri­to­ries and ge­net­ics.

Cal­i­for­nia gray whales oc­cupy mostly wa­ters closer to North Amer­ica, while the much smaller west­ern Pa­cific gray whale pop­u­la­tion was thought to roam the eastern Asia coast.

Re­cently, sci­en­tists over two mi­gra­tory sea­sons tagged west­ern Pa­cific gray whales off Rus­sia’s Sakhalin Is­land, hop­ing to dis­cover ex­actly where they spend win­ters.

The sci­en­tists were ex­pect­ing west­ern whales to mi­grate to breed­ing and calv­ing grounds some­where in the South China Sea, said Bruce Mate, direc­tor of the Marine Mam­mal In­sti­tute at Ore­gon State Uni­ver­sity and lead au­thor of a re­search pa­per pub­lished this week in the jour­nal Bi­ol­ogy Let­ters.

In­stead, three whales with satel­lite tags were tracked swim­ming east and across the north Pa­cific to Alaska wa­ters and into the mi­gra­tory route of Cal­i­for­nia gray whales, also known as eastern Pa­cific gray whales.

West­ern Pa­cific gray whales, once thought to be ex­tinct, are the most en­dan­gered of the large whales, Mate said. Only 150 re­main as the re­sult of over­hunt­ing.

To pro­tect them, en­vi­ron­men­tal groups have cam­paigned against industrial ac­tiv­i­ties such as oil and gas devel­op­ment off Sakhalin.

Fed­eral and in­ter­na­tional whale ex­perts have con­sid­ered the two sub­pop­u­la­tions of gray whales to be dis­tinct be­cause their ter­ri­to­ries were thought not to over­lap, based on his­toric whal­ing data, and be­cause of ge­net­ics analy­ses, Mate said. Those con­clu­sions are be­ing reeval­u­ated, he said.

The tag­ging project be­gan in Septem­ber 2010 and was done with sci­en­tists from the In­sti­tute of Ecol­ogy and Evo­lu­tion of the Rus­sian Academy of Sciences, the Kronot­sky State Na­ture Bio­sphere Re­serve and the Kam­chatka Branch of the Pa­cific In­sti­tute of Geog­ra­phy.

The sci­en­tists were star­tled when a 13-year-old male whale they named Flex swam east to U.S. and Canada wa­ters. He was tracked to the Ore­gon coast un­til his tag was lost.

A year later, a 6-year-old fe­male named Agent was tracked half­way across the Gulf of Alaska be­fore her tag was lost.

A third whale, a 9-year-old fe- male dubbed Var­vara, was tracked all the way to Baja Mex­ico, where most Cal­i­for­nia gray whales breed and give birth.

Var­vara spent 42 days off Baja Cal­i­for­nia and vis­ited the three main breed­ing ar­eas of the Cal­i­for­nia gray whale. She then swam north and west and re­turned to Rus­sia wa­ters, cross­ing the Ber­ing Sea near re­treat­ing sea ice in May 2012. Her trip took 172 days.

The nearly 22,500- kilo­me­ter swim is the long­est recorded mi­gra­tory jour­ney by a mam­mal by more than 1,900 kilo­me­ters, Mate said. The big­ger ques­tion, how­ever, is whether the west­ern whales are rem­nants of a dis­tinct pop­u­la­tion of en­dan­gered an­i­mals or the west­ern­most feed­ing group of fully re­cov­ered Cal­i­for­nia gray whales.

Biop­sies and photo iden­ti­fi­ca­tions in­di­cate 30 of the west­ern whales have made the cross­ing to North Amer­ica, Mate said.

How­ever, there also is ev­i­dence that west­ern Pa­cific gray whales are not ex­tinct, ac­cord­ing to the pa­per. Four west­ern gray whales died in fish­ing nets off Ja­pan be­tween 2005 and 2007; a gray whale was stranded off south­ern China in Novem­ber 2011; an­other was sighted in Mikawa Bay, Ja­pan, in March 2012.

AP

This Sept. 13, 2010 photo pro­vided by the Ore­gon State Uni­ver­sity Marine Mam­mal In­sti­tute shows a west­ern Pa­cific gray whale near Sakhalin Is­land in Rus­sia.

Newspapers in English

Newspapers from Taiwan

© PressReader. All rights reserved.