Something Wild: Seals at Isles of Shoals
On a Tuesday morning last summer, Chris Martin boarded the John B. Heiser, a 33-foot research vessel, headed for Duck Island. Mission: to count seals.
The census is conducted by Shoals Marine Laboratory, and the small but hearty troupe on board include Ian Breslow, a recent grad from Cornell University and intern at Shoals. His charge on this outing is photography, a critical element for determining an accurate count. From 50 yards, one seal looks very much like another, but zooming in on digital photos later in the lab makes it easier to count the seals and find identifying markers, and to differentiate between the gray seal and its smaller cousin, the harbor seal.
Before long the engine slows down, we’ve arrived at our destination: Duck Island and the many rock ledges that surround it. There’s not much to Duck Island, It’s small, remote, uninhabited; in short, a perfect place for seals to “haul out.” And it’s time for Ian to get to work.
If you’ve not been out Duck Island way, there are a lot of rock ledges, and the team at Shoals Lab has named each one, even designating the north and south sides of many of these rocks. So as Ian snaps away, he periodically calls out an exposure number to his fellow crew member, taking notes. And once in a while, he announces which ledge he’s aiming the camera at. This is essential to organizing the data once they get back to the lab.
We inch a little closer to the ledges, and Ian snaps furiously away pictures of dozens and dozens of what look like plump furry logs bathing in the sun. Heads pop up among the piles of seals as they catch the sound of our boat and a few of them get a little wary and start to edge toward the safety of the water. But soon everyone settles down, and we get to Ian’s favorite part of these surveys…vocalizations! “They’re adorable…it’s almost like they’re singing.” We cut the engine and drift. And before long, just above the sound of the wind and the water, we can hear…singing. It’s a bit like the cooing of a pigeon pitched down an octave or two.
With the engine off, it isn’t long before the wind blows out of ear shot of the seals, so we start up the motor and head back to the lab to take a closer look at Ian’s photos. The populations of both gray and harbor seals in this corner of the Gulf of Maine are on the rise, and today’s census confirms that. Ian points out that “gray seal population is increasing by a much larger margin than the harbor seals. We believe that is because the gray seal was extirpated from this whole region until the 1960s and 1970s.” For a couple of decades there were no gray seals around here, and in the last few decades they’ve been making a strong comeback as they and the ecosystem look for that balancing point.
And there’s more they can glean about the changing ecosystem from the photos they take. It’s hard to see from the boats but many seals bear wounds. Once we get the photos back to the computer we can better see the wounds from propellers, from fishing nets, and from sharks. Ian says he’s seen, “two seals that may have evidence of shark attack but that’s only two of the 4-600 we see on surveys.”
An increase in a prey species, like seals, is bound to attract predator species. Shoals Lab is working with the Atlantic White Shark Conservancy to track white sharks in the area each summer and find out if there is a corresponding rise in their numbers.