The California Department of Fish and Game said Friday that "Olive the Oiled Otter" was spotted swimming on her back with her pup resting on her belly three years after being rescued near Santa Cruz.
Oil damages otters' fur coats, exposing them to the elements and hypothermia.
After being cleaned, Olive was released and outfitted with a microchip and transmitter, allowing scientists to track and study her.
When she was brought in for a checkup this summer, scientists discovered she was pregnant.
(Copyright 2012 by The Associated Press. All Rights Reserved.)