After years of research on dolphin behavior and under pressure from animal rights groups, the National Aquarium in Baltimore has decided to move the marine mammals to a sanctuary, officials said Wednesday.

It will be the first sanctuary for dolphins in North America.

The transfer from the aquarium in the Atlantic coast port city will not be done before 2020, they said.

The venue for the dolphins will be a protected coastal habitat, where the animals will continue to live under human care.

"We now know more about dolphins and their care, and we believe that the National Aquarium is uniquely positioned to use that knowledge to implement positive change," said John Racanelli, chief executive officer of the National Aquarium.

"This is the right time to move forward with the dolphin sanctuary."

Management and the board of directors at the aquarium in Baltimore, near Washington, started working on a strategy for the dolphins five years ago.

Many ideas were floated, including rebuilding the existing marine mammal facility, which is 25 years old, to create a more natural-style setting.

Transferring the dolphins to other licensed facilities was also considered.

But officials ultimately decided to set up a coastal refuge with National Aquarium staff continuing to take care of the dolphins and interacting with them.

"This is a special time in history concerning evolving attitudes about treating all forms of life with dignity and respect -- other humans very much included," said Sylvia Earle, a marine biologist, explorer and author.

"The idea of providing sanctuaries for elephants, chimpanzees, big cats -- and now dolphins -- is a sign of a maturing ethic of caring unthinkable in past millennia, centuries and even decades."

The venue, in a tropical or subtropical location, will also contain natural stimuli for the dolphins, such as fish and sea plants. Its location was not immediately announced.

The National Aquarium is seeking donations to fund the sanctuary.