Humpback Whales Bubble Fishing – BBC Earth (2015)

Cetaceans are the largest animals on our planet. Whales could evolve into such enormous sizes only very recently through the geological time. This became possible due to pulses of nutrients coming from a cycle of glaciations fertilizing the seas for plankton growth. Feeding efficiency is a prerequisite for gigantism to evolve.

Truly gigantic animals have always been close to the base of trophic levels and have found a way to maximize feeding on a rich food resource. Sauropod dinosaurs for instance have tiny heads with small incisor teeth and just enough muscle power to nip and swallow. A small skull enabled evolution of a very long neck in Sauropods. Long neck might even have been a sexually desired trait which enabled high reproductive success. Small skull and long neck combination maximized feeding efficiency even reaching tall coniferous trees like the monkey puzzle tree (Araucaria araucana). All plant material was being swallowed whole and entire digestion took place withing the massive abdomen providing sufficiently long tract. Long neck enabled minimal movement but maximal feeding radius. They resembled vacuum cleaners of the 70s.

Whales on the other hand are another fascinating natural history story for evolution of gigantism.

In aquatic ecosystems most organisms are cold-blooded and don’t waste energy in the form of body heat like those living on land. For that reason food chain can be many trophic levels longer. The humpback whales (Megaptera novaeangliae) are the only whales “fishing”. They have developed a strikingly impressive method of cooperative hunting for herring. Killer whales also hunt fish but are not whales (they are very large dolphins).

Dolphins in Florida have been filmed hunting similarly but using mud instead of bubbles in very shallow water. Dolphins have also developed a different method in tidal marshes of South Carolina called strand fishing.

North Atlantic humpback whale population has been under observation for quite a long time. A large catalog of whale photographs enable identification of individuals based on their tails. Every whale has a unique identifiable tail shape. One curious observation is a new behavior called “loptail feeding” that spread among humpbacks of the Atlantic. The behavior was first recorded in one whale in the Gulf of Maine in 1980. Since then, 278 humpback whales—out of about 700 observed individuals that frequent the Stellwagen Bank (a famous location for endangered Right whales) have learned it. Spreading of a learned behavior is regarded as an evidence for culture.

A cutting-edge and non-intrusive method of whale observation comes from drones. Researchers from Oregon State University’s Marine Mammal Institute have been observing the world’s largest animal in the Southern Ocean off Australia. Blue whales cruise fast at 6.7 mph according to Leigh Torres explaining in the following video. When an individual encounters a decent mass of krill it flips on its side, mouth wide open, to plow into its meal target at 1.1 mph. The maneuver is called “lunge feeding”.

Blue whales have evolved a great skill for assessing the profitability of the krill patches. They don’t attempt lunge feeding if the krill mass is not large enough. Blue whales bother to feed only when the payoff is likely to be worth the incredible amount of energy required to slow down their massive bodies and then accelerating back to cruising speed.

 

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