The so-called Arctic 30 are currently in an isolated port city on the northwestern tip of Russia.
Alexandre Paul of Montreal and Paul Ruzycki, of Port Colborne, Ont., were among those arrested on the Greenpeace ship Arctic Sunrise on Sept. 18.
They were detained after a protest at an oil-drilling platform in the Arctic Ocean and taken to the remote port city of Murmansk, and are now charged with hooliganism.
The activists could see a transfer to a jail in St. Petersburg in the coming days, the environmental organization says, quoting diplomatic sources.
Paul talked to his mother Friday night, speaking to her on the phone for about 30 minutes. He told her he has been learning Russian, and that while he has lost weight he has not been mistreated.
In a recent letter, he said the Murmansk prison was cold and that the activists had been separated from each other.
St. Petersburg jail closer to consular services
St. Petersburg will offer more sunlight than the current location, in the Arctic Circle. It's also closer to consular services.
But Greenpeace said it doesn't mean the conditions at the new facility will be any better.
The organization's director, Kumi Naidoo, said the detainees should be freed.
"The detainees shouldn't be in jail at all. They should be free to be join their families and to restart their lives," he said in a statement.
Greenpeace said it doesn't know the reasons for the move, and isn't sure of the transfer details either.
"Murmansk is the largest city inside the Arctic Circle and is over 1,000 kilometres from St Petersburg," said Patrick Bonin, climate and energy campaigner, in an email.
"We don't know exactly how they will make the trip, or when."
Despite earlier reports that Russian authorities had pledged to reduce charges the activists are facing - from piracy to the lesser charges of hooliganism - Greenpeace now says the piracy charges were never dropped.
The group says some of the activists face both kinds of charges.
The piracy charge carries a maximum 15-year sentence, while the hooliganism charge carries a maximum seven years in jail.