June 3, 2013
In April Charlie the southern sea otter returned to the Aquarium after a two-year stay at the Long Marine Lab in Santa Cruz, California, where he participated in a study of sea otter hearing. During his absence, another male sea otter, Odin, lived at the Aquarium. Odin was the original subject for the Long Marine Lab study, but was determined to be a less-desirable candidate because he appeared to have some hearing loss.
Principal Investigator Dr. Colleen Reichmuth and Laboratory Research Coordinator Asila Ghoul conducted the study, which was the first of its kind in investigating sea otter hearing. Its goal was to establish a baseline for capability across their hearing range. Gathering this data is important, the researchers say, because it can inform decisions made by government agencies regarding the impact of human activity on marine environments. Human activity that produces noise that may impact sea otters includes coastal construction, oil and gas production, military and harbor operations, dredging, and transportation, both commercial and recreational.
Charlie was selected as a good candidate for this study, in part, because of the behavioral training he had received at the Aquarium. “The animals have to be really very well-trained and cooperative partners in the research,” Reichmuth explained. “Just what we’re learning from Charlie is going to make a really significant contribution to what we know about the entire species. Charlie is going to be an important representative for the entire [sea otter] population.”
Reichmuth and Ghoul tested Charlie’s hearing both above and below water. To participate, Charlie learned to enter a specialized acoustic testing environment, listen for sound signals, and respond to the researchers, notifying them whether or not he had heard the sound by touching his nose to a target or remaining still.
Ghoul will present a lecture at the Aquarium on June 25 to share details of the study’s findings and stories of Charlie’s experiences during the research.
As a standard procedure, Charlie will be quarantined for one month before being reintroduced to the public exhibit and the Aquarium’s other sea otters. Husbandry staff members estimate that Charlie will be back on public exhibit before the end of May.