What do Minke Whales do in the estuary of St. Lawrence?

The minke whale is a fast and agile predator, but as with any marine mammal, it must come to the surface to breathe. This is the compromise between the need to feed below the water surface and oxygen needs. It must organize its activities accordingly. To do this, it alters the duration of its dives and surface time based on its various activities.

Studies conducted in the Estuary have shown that minke whales adjust their surface time and number of breaths depending on the time they spend under water. If the animal remains under water for an extended period, it will take more breaths when it resurfaces in order to recover. This phenomenon is observed when the minke whale performs a deep dive or when it engages in manoeuvres to herd prey under water. When travelling, surfacing to breathe causes a loss of energy compared to continuous underwater swimming. It therefore more advantageous to stay under water over a greater distance. At rest, its energy consumption approaches zero and it does not seem to show any particular breathing pattern.

Minke whales even develop different feeding tactics depending on their environment. In the Estuary, they swim in circles, ellipses or hyperboles; they also use currents, rock walls and occasionally even the hulls of boats to trap their prey. Some of them jump out of the water and land noisily on their belly or side. Perhaps they do this to stun their prey or scare the fish so that they form a tighter school. Others have invented their own personal techniques. This is the case of Loca, a faithful visitor to the mouth of the Saguenay, who feeds by means of “frog jumps”, lifting its head out of the water and striking the surface. Recently, in Les Escoumins, the Mériscope team observed a minke whale that suddenly rolled onto her back with its pectoral fins nearly emerged, attempting to engulf prey caught between its stomach and the water surface.

Pour en savoir plus:

Structure and Dynamics of Minke Whale Surfacing Patterns in the Gulf of St. Lawrence, Canada