Seal eating habits revealed by cameras attached to mammals

Scientists at Dalhousie University in Halifax say footage from cameras attached to seals more than a decade ago continue to offer insights into a top marine predator.

The cameras were attached to adult male seals at Sable Island as far back as the mid-1990s and the data is still being used today to generate new insights into how seals feed in the depths of the ocean.

"It's just so amazing to see the world from the seals point of view," said Sara Iverson, a biology professor and scientific director of the global Ocean Tracking Network.

Iverson and other scientists at Dalhousie University have just published a scientific paper in the Canadian Journal of Zoology using the critter cam data that tested theories about harbour seal diving and feeding behaviour.

The project — a joint effort with National Geographic — involved capturing 32 adult male harbour seals at Sable Island and mounting cameras on their backs for three days each. It resulted in approximately three hours of video per seal.

Some images show seals taking larger food items to the surface or resting on the bottom. One camera shows a harbour seal rooting in the sandy sea floor for its preferred prey — the sand lance — then vomiting its stomach contents and slowly reconsuming them.

"What we think happened was that his stomach was so full of sand that this was a way to rid his stomach of all that excess sand," said Iverson.

The harbour seals captured in these videos are likely long gone by now.

"Over a period of about four or five years, sharks totally decimated the harbour seal population. There's no longer a viable feeding population over on Sable," she said.

The Ocean Tracking Network has started another Sable Island research project. They recently installed six acoustic receivers to track encounters between grey seals which have survived and great white sharks.

Data from the Sable Island receivers will be offloaded in mid-May.