Oil-fed Otters May Provide Clues to Spill Damage
When the Exxon Valdez ran into Bligh Reef in the spring of 1989, the most visible victims of the oil spill were blackened sea otters and shore birds. Now, nearly a decade later, scientists are still trying to sum up the effects of the oil spill.
In Seward, one researcher is trying to learn more about the spill by feeding small amounts of crude oil to river otters. Merav Ben-David, an ecologist who studies animal behavior and physiology at the University of Alaska Fairbanks' Institute of Arctic Biology, is performing research on river otters that began right after the spill.
In 1989, UAF Professor Terry Bowyer, a wildlife biologist at the Institute of Arctic Biology, Professor Larry Duffy, head of UAF's Chemistry and Biochemistry department, and technicians from the Alaska Department of Fish and Game began examining river otters in oiled and non-oiled areas. The scientists chose to study river otters because the animals often live where the land meets the sea. River otters, seldom-seen members of the same family as mink and sea otters, den along bodies of water in the forests of Alaska. The animals, which grow to four feet long, hunt in rivers, the ocean, and sometimes on land. River otters on the coast catch much of their diet--fish, crabs and shrimpfrom the sea.
Bowyer, Ben-David and graduate student Gail Blundell have studied river otters in Prince William Sound for the past three summers to look for lingering effects of the oil spill. Otters are notoriously hard animals to study--they are shy and too smart to come to a trap twice--so Blundell and Ben-David captured 15 river otters from different areas within Prince William Sound and brought them to the Seward Sea Life Center.
When river otters were first studied, right after the spill and the three years following, researchers found enzymes in the otters' blood indicating stress that could be caused by ingesting crude oil. Otters that lived near oil-fouled beaches showed high levels of the enzyme; otters in areas without oil showed much lower levels.
Today, the otters living near shores that were soaked by oil nine years ago are still showing elevated levels of the stress enzyme. Though crude oil is no longer visible, otters may still be suffering from its effects. That's what Ben-David hopes to find out as she feeds crude oil to some of the otters at the Seward Sea Life Center.
Ben-David has a small metal jug of crude oil given to her by ARCO workers at Prudhoe Bay. She and assistant Olav Ormseth will fill tiny capsules with the oil, slip the capsules inside herring, and feed the herring to the otters four times each week. Five otters will receive the heaviest dose of oil--1,000 parts per million, about the equivalent of a tablespoon of oil in five gallons of water. Five will get a dose ten times smaller, and five will ingest no oil whatsoever.
Ben-David said she is basing the highest dosage on oil levels found presently in blue mussels that live in Prince William Sound. Ben-David and Ormseth will take blood samples from the otters every three weeks to see if the crude oil is causing the stress enzymes to increase. Using underwater cameras, they will watch otters to see if their diving ability is impaired by the crude oil, which can cause anemia. The researchers will continue feeding some oil to the otters for 100 days, Ben-David said. Then, she will stop feeding them oil for 100 days before she releases them in March 1999.
By feeding a toxin to one of the cutest mammals in Alaska, Ben-David expects a bit of opposition. She said feeding oil to otters is the next logical step in her study, a step that will help determine how much oil spills affect living creatures, and for how long. "It's extremely important to validate those results we're getting out in the field," she said. "These results will be very useful for future oil spill work. We can use the otters as a model for all marine mammals affected by oil."
