According to the Telegraph, the penguins have shared a faithful partnership for almost their "entire breeding life," despite "spending long periods apart and each of them taking solo trips totaling 200,000 miles."
For the past 16 years, the penguins have returned to the same nest (and each other) to produce and care for a new clutch of chicks.
The researchers, led by Pablo Garcia Borboroglu of the National Research Council of Argentina, said they were surprised to find such a long-lasting penguin partnership.
Previously, penguin couplings were believed to last between five and 10 years, with "many cut short by the unexpected death of birds during migration," ANI reports.
“It is unbelievable how far Magellanic penguins swim -- and each breeding season they come back to the same nest and to the same partner,” Borboruglu said.
"Divorce" in penguin relationships is also a possibility, however, as pairs that are unable to hatch chicks will "break up" and find new partners.
Researchers have been following the Magellanic penguin colony in Punta Tombo, Argentina, since 1982. To date, 50,000 penguins have been identified with name tags. The birds are now also tracked using a satellite-tracking system.
The updated research from the project was revealed recently during a lecture to the Whitley Fund for Nature in London, writes ANI; the findings will also be published in a new book by Borboroglu next year.
According to the Wildlife Conservation Society (WCS), Magellanic penguins breed in Argentina, Chile and the Falkland Islands.
The penguins -- which were named after explorer Ferdinand Magellan, according to the WCS -- face threats from commercial fishing, oil pollution and climate change.