A strange sound has oft' been heard in Haro Strait by the fixed hydrophones of the OrcaSound array. During the summer months (approximately July through September), the "heavy breather," puts a tremendous amount of acoustic energy into the water. The sound occurs day and night, is usually repeated 10-15 times in a particular sequence. Each sequence is followed by 1-5+ minutes of silence. Within each sequence, the sounds are separated by 30-90 seconds of silence. The sounds also get progressively louder and longer until the middle of the sequence and then get softer and shorter by the end.

Visual observations of a harbor seal that resides in a kelp bed just south of the array correlate with the sound sequences. The seals head is consistently above water during the inter-sequence silences. The seal is submerges 5-30 seconds before a sequence begins and emerges within 10-120 seconds after the sequence ends.

Similar recordings and observations in California confirm that the sound is a harbor seal, and probably a male. Yet some questions remain unanswered, like: how is the sound made and what is its purpose?

Example sound files

Each .wav file is about 1.9Mb and its name indicates the date (MM_DD_YYYY) and time (HH_MM_SS) of the sample...

• long (classic)
• long
• medium
• short
• short
• short
• in the rain

A similar sound is apparently emitted by hooded seals (near Norway?)... Here is an example from ocean-sounds.com:

• "Roar" of an adult female hooded seal
  

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