Friday, July 15, 2016

Mysterious little harbor seals...

So far, the harbor seal data collection has gone about as good as could be expected for any new protocol.  I had a few set backs early on with equipment, which have since been resolved, and there’s also been a lot of forward progress, which is great.  The part I’m struggling the most with, actually, is the part I thought wouldn’t be a problem at all – where are the seals that are vocalizing underwater. 

Harbor seal in the foreground, glacier in the background (Photo: L. Matthews)

I looked at the acoustic data from last year, and harbor seals are vocalizing all the time.  During the breeding season, male harbor seals set up underwater territories and defend them acoustically – makes sense that they would vocalize all the time.  I kayaked around our survey area the first few days we were here, and harbor seals are popping up everywhere – seems like there would be a lot of territories. 

In an ideal world, I drop a hydrophone from my kayak near where an individual is vocalizing, that individual vocalizes for a bit and then pops his head up out of the water to take a few breaths.  When that individual is at the surface, I take his photo and his position.  If I do this enough times, I can get a general idea of the size of size of this animal’s territory and compare that to the locations of the vocalizations underwater.   I can also associate the vocalizations I’ve recorded to specific animals and look at variation in vocalizations between individuals.

The view from my kayak office is kind of amazing (Photo: L. Matthews)

After some days of dropping the hydrophone and listening, I found a few places where the harbor seals roared loudly.  I sat in these spots and watched and waited for a harbor seal to pop up within sight range of the kayak, but nothing!  Multiple times now, we’ve made recordings of harbor seals, and we’re definitely close to where they’re vocalizing, but they never actually make an appearance at the surface.

I don’t know why it appears that my vocalizing animals never come to the surface.  I’ve got a little tinkering to do with the data that might clue us in as to where they are, but as of right now, your guess is as good as mine.

FUN SCIENCE FACT #45: Harbor seals may not be very agile on land, but in the water, they can swim up to 15mph to escape predators.  Most of the time though, they cruise around at a much more casual pace.

Harbor seal swimming gracefully in the cold waters of Glacier Bay (Photo: L. Matthews)

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