Tracking marine mammals

OSU’s Marine Mammal Institute (MMI) grew out of a COMES research program to better understand marine mammal management issues. MMI director Bruce Mate has led tagging studies of several whale species over the past three decades, monitoring more than 300 giants of the ocean to reduce risks from human activity. Building on knowledge developed by the whale tagging program, research continues at COMES in partnership with MMI, focused on the genetics of whales and dolphins and the ecology of seals and sea lions.

One question that needed an answer was why northern sea lions, also known as Steller sea lions, have been steadily disappearing. To understand the fate of individual sea lions, OSU researchers developed a tiny transmitter that is implanted in a sea lion to record temperature, light, and other information for up to 10 years and transmit the information to the OSU lab in Newport.

[caption caption="Steller sea lions, a threatened species, are tracked by OSU scientists. (Photo courtesy of NOAA.)"][/caption]

“The transmitters record details throughout the animal’s life and, at the end, can suggest when and how the animal has died,” said Markus Horning, an OSU pinniped specialist who leads the project. If a sensor detects a rapid drop in temperature and sudden sensing of light, the sea lion may have been killed and quickly dismembered by a predator. Gradual cooling would be a sign of death without dismemberment—perhaps from disease, starvation, drowning, or shooting.

Data so far suggest that predators are targeting younger pups, preventing many juveniles from reaching breeding age. With an 80 percent decline in northern sea lion populations over the past 4 decades, predation may be more prevalent than scientists previously thought, Horning says. He hopes this research can eventually lead to management strategies to help rejuvenate this threatened species.