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Coastal cetaceans, harbour porpoises visit the St. Lawrence by the thousands.

But you need a keen eye to catch the fleeting passage of their little black back on the surface.

Laurent was one of the first occupants of the Marine Mammal Interpretation Centre. Not much is known about this individual, however. Indeed, there is no identification catalogue for harbour porpoises in the St. Lawrence. As a result, very little is known about the life histories of individuals like Laurent.

Silhouette of a porpoise with a question mark.

We know very little about Laurent’s death. Judging by the size of its skeleton, we do know that it was less than a year old.

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At low tide, on the rocky, seaweed-covered shore, a man in chest waders stands over the carcass of a tiny porpoise.

Less than one year old when it died, Laurent was probably still dependent on its mother’s milk. Even though she was still nursing her calf, Laurent’s mother may have been carrying another baby porpoise in her belly.

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Two porpoise backs with their triangular fins are visible on the water surface. The porpoise in the foreground is smaller than the one behind it.

Male porpoises also lead intense lives. Although they are about the same size as a human, harbour porpoises have reproductive organs on an entirely different scale! A porpoise’s penis is approximately 50 cm long and its testicles account for about 5% of its weight.

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Underwater view of a male harbour porpoise with its erect penis. The penis is about a quarter the length of the animal.

Porpoises are often mistaken for dolphins, but these animals represent two distinct families of cetaceans. There are tricks to telling them apart at sea, but they can also be distinguished by examining their teeth.

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The back of a porpoise with its triangular dorsal fin.

Harbour porpoise

The back of a dolphin with its sickle-shaped dorsal fin.


The skeleton of a porpoise differs from that of a dolphin, but it also has similarities. In fact, it even shares certain similarities with all other mammal species!

A skeleton tells us a lot about the life and evolution of an animal!

Whales have fingers! However, it is only by looking at a skeleton like Laurent’s that one can see them. In fact, the pectoral fins of cetaceans are made up of the same bones as our arms, but unlike humans, they have just a single joint at the shoulder.

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Comparison of the skeletons of a porpoise and a human. Different parts are identified: the skull, the vertebrae (cervical, thoracic, lumbar and caudal), the ribs and the bones of the forelimbs (arms), namely the scapula, humerus, radius and ulna. The vestigial bones correspond to the hind limbs in humans.

Who were whales’ ancestors?

The animal considered to be the first cetacean is Pakicetus. And it walked on all fours! Measuring between 1 and 2 m long, this carnivorous mammal ventured into the water to find its food.

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Drawing of a four-legged mammal with an elongated head and a long tail

How did whales go from a four-legged mammal to their present form?

It can be hard to imagine that an animal like Pakicetus could be the ancestor of whales. But one must not forget that this evolution occurred over the span of millions of years.

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Timeline showing various milestones in the evolution of cetaceans. 55 million years ago: appearance of Pakicetus 50 million years ago: appearance of Ambulocetus 47 million years ago: appearance of Rodhocetus 38 million years ago: appearance of Dorudon 25 million years ago, whales split into two groups: odontocetes and mysticetes.

Whale or cetacean: What’s the difference?

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Phylogenetic tree of cetaceans. A first branch appears when toothed whales (odontocetes) diverged from the baleen whales (mysticetes). In baleen whales, a branch separates members of the family Balaenopteridae (e.g. blue whale) from those of the family Balaenidae (e.g. right whale). With regard to toothed whales, a first branch separates the family Physeteridae (e.g. sperm whale) from the others, a second branch is represented by Ziphiidae (e.g. bottlenose whale), a third branch is represented by Delphinidae (e.g. white-sided dolphin) and a fourth branch is represented by Monodontidae (e.g. beluga) and Phocoenidae (e.g. harbour porpoise).

A porpoise like Laurent may be similar in size to its land-roaming ancestors, but how do we explain the giant size of today’s blue whale and other mysticetes?

In fact, the first mysticetes were not all that big, but a cooling of the Earth’s climate some 4.5 million years ago is believed to have led to ever larger animals.

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Diagram comparing the size of a harbour porpoise with that of Pakicetus, a human, an elephant, Diplodocus and a blue whale. Harbour porpoises and Pakicetus are about the size of humans, while blue whales are larger than a Diplodocus.

Although whale studies have already enabled us to unravel a number of mysteries, we still have much to learn and discover. Knowledge gaps represent an obstacle to the protection of several species...

Whales spend over 90% of their time under water, where they go undetected by human observers. Studying them therefore presents an additional challenge. It is difficult to quantify a population or properly characterize its distribution.

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View of the St. Lawrence. Not a single whale disturbs the calm water surface.

For harbour porpoises like Laurent, a lack of information prevents us from determining whether this population is decreasing, increasing or stable...

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A group of four porpoises rise to the surface. The back and dorsal fin of the first three are visible, but are cropped off in the fourth individual.

Considering the other threats faced by the species such as by-catch in fishing nets, the population status of the harbour porpoise in eastern Canada is classified as “Special Concern”.

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A porpoise carcass floats on its side.

What can be done to fill current knowledge gaps?

Research boat with three crew members and their tracking tools.

Invest more in scientific research.

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A woman speaks at a conference podium at the Cruise Canada New England Symposium in Boston in 2018

Promote knowledge sharing

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What can be done on an individual level to address these knowledge gaps?

By caring and learning about cetaceans, we contribute to knowledge sharing and the importance we place on them in our society.

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A woman (wearing a vest with the GREMM logo) points to multiple whale images on a wall while a man looks at what she is showing.

Now that you’ve heard Laurent’s story, let’s go meet the other whales!

See the skeleton in 3D
Fact sheet
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