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A Seal Mystery

February 14, 2014

Melting sea ice allows marine mammal species that were once isolated to intermingle – and share diseases.



Solving a seal mystery. I’m Bob Hirshon and this is Science Update.

800px-Foka_szara_mateusz_wlodarczyk grey seal

Grey seal. (Mateusz Wlodarczyk/Wikipedia)

In March of 2012, 20% of the grey seal pups born on Hay Island in the Canadian Maritimes mysteriously died. An investigation pointed to a parasite called sarcocystis canis, never before seen in the species. Molecular parasitologist Michael Grigg and his team traced its origin to ringed seals living thousands of miles away in the Arctic. So, how did it reach grey seals? Grigg, who works for the National Institutes of Health, blames global warming.

MICHAEL GRIGG (National Institutes of Health):

Normally, the ringed seal has been shut off from other roaming marine mammals due to the polar ice cap. So it’s only been in the last few years that we’ve started to see the ringed seal and the grey seal starting to intermingle as grey seals are chasing fish supplies further north.


He says the parasite proved deadly in grey seals because, unlike ringed seals, they haven’t evolved resistance to it yet. I’m Bob Hirshon, for AAAS, the science society.

Pusa_hispida_ringed seal pup Shawn Dahle NOAA wiki

Ringed seal pup. (Shawn Dahle/NOAA)