Ribbon seal (Histriophoca fasciata) is a seasonally ice-associated species. They rest, whelp, and molt on pack ice in spring. From summer to winter, these seals are pelagic and rarely haul out. For this reason, they are hard to observe and little is known about their underwater behavior.

In this study, we analyzed underwater sounds of ribbon seals recorded with AURALs (Autonomous Underwater Recorder for Acoustic Listening, Multi-Électronique, Inc,) from September 2009 to May 2010 in the Bering Sea. Recordings were made with a duty cycle of 9 minutes on and 11 minutes off and a sampling rate of 8192 Hz (for an effective bandwidth of 10-4,096Hz). Ad-lib recordings were conducted in the Okhotsk Sea with C53 (Cetacean Research Tech.) only when seals were detected by sights in pack ice area. Recordings were made with a sampling rate of 44,100 Hz (for an effective bandwidth of 14-22,050 Hz).

In the Bering Sea, the majority of ribbon seal calls (sweep sounds) were detected only in April and May, though some individuals seem to occur in this area throughout the year. It is possible that these calls are related to their breeding behavior because their breeding also occur in April and May in this area. In the Okhotsk Sea where ribbon seals breed earlier than Bering Sea, calls were detected in the end of March. We’ll discuss possible causes of this seasonality in the recorded ribbon seal calls.