slew of beaked whales and striped or polka-dotted dolphins are among the most elusive creatures of the sea, but a Canadian-trained biologist has managed to document them.

Robin Baird, who studied at Dalhousie and Simon Fraser universities, has spent 13 years tracking and studying rare marine mammals off the coast of Hawaii.

The Longman’s beaked whale, for example, turned up just once in those years of surveying, which has covered 84,758 kilometres.

Evidence so scant means that telling one of the 18 rare species from another has been a huge challenge to Baird and his team.

The adult male melon-headed whales and pygmy killer whales are distinctive, but when you throw the nondistinctive females or the Cuvier’s beaked whales and the Blainville’s beaked whales into the mix, things can get confusing.

The differences, Baird told the Star, can be “really subtle.”

So subtle, in fact, that veteran whale experts got it wrong.

“In the way we do our work, we’re lucky in what we’re able to do.”

In a small, nimble boat, and with both the advantage of experience and the possibility that each year’s funding could be the last, Baird and his fellow Cascadia Research Collective biologists used photographs, acoustic signatures, genetic evidence and satellite tags to tell one rare mammal from another.

What are the odds they’re missing new species or confusing others?

“With the beaked whales, quite high,” Baird said, if it’s based only on visuals.

The high-frequency acoustic evidence is crucial for some species, but there are others for which they can’t yet tag the sounds. In those cases, the scientists keep trying for a genetic sample, using a crossbow to snare “a little skin or blubber samples.”

So far, said Baird, they have more than 1,000 genetic samples from 10 different species.

Finally, satellite tagging has allowed them to keep track of mammals such as the false killer whale, which spent half their time on the inaccessible windward side of the islands.

Their research, published in a recent paper in the journal Aquatic Mammals, has enabled the scientists to understand where and how these rare mammals breed, congregate, feed and interact.

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Striped dolphins, for example, “actively avoid boats,” unlike their more familiar bottle-nosed cousins.

“They live in very, very deep water. You don’t start to see them until you’re more than 3,500 metres deep.”