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What is Netting with bubbles-whale hunting?

 

"Netting" with bubbles-whale hunting

Not all members of the whale family are as agile and good at hunting as killer whales and dolphins. Huge species such as humpback whales will suffer a lot when catching agile fish. As a result, these deep-sea monsters have evolved very sophisticated hunting techniques. The bubble net feeding we are going to introduce today is one of them.

All animals in nature have two basic instincts, namely foraging and reproduction. Reproduction is to ensure the continuation of genes, so I won’t go into details today. The fundamental purpose of foraging is to continue its own existence, so as small as an individual animal, as large as an entire population, having an efficient foraging strategy increases the chance of survival.

 

There are many ways of foraging for animals in nature. Some take the initiative, some wait for rabbits, and some have evolved a very sophisticated way of foraging, which is so sophisticated that it requires acquired learning to master it. The bubble net feeding we talked about today is the special feeding method of some cetaceans represented by humpback whales.

 

What is bubble net feeding?

We all know that whales can be roughly divided into two categories based on their body structure: toothed whales and baleen whales. Toothed whales are those whales with teeth in their mouths, such as giant sperm whales, ocean killer killer whales, and petite and flexible dolphins and porpoises. When these whales hunt, they only need one bite to solve the problem.

 

But baleen whales represented by humpback whales are not so simple to fill their stomachs. Because they lack chewing teeth, they can only prefer to catch groups of small fish and shrimp. In some cases, the concentration of these small prey is very high. 

The large baleen whales only need to rush into the fish and shrimp schools, and open their mouths to bring the fish and shrimps in with the seawater. For example, the blue whales use krill to prey. 


But sometimes, the distribution of these small fish is relatively scattered, and the speed of the fish school is very fast and flexible, and the effect of direct predation is very poor. 

Humpback whales often encounter this embarrassment when they prey on herring and juvenile salmon. However, as the "old mage" in the ocean, humpback whales are well versed in the essence of "gathering monsters first, then AOE"-humpback whales will spit out bubbles in a spiral from below the school of fish, eventually forming a circular air curtain big net. 

This is what we are talking about today (bubble net feeding).

 

In 1929, whalers observed this habit of humpback whales for the first time in the waters near Norway: they were seen in groups of three to five, and several whales continuously released bubbles around the school of fish, forming a gas curtain wall. The school of fish spins anxiously in the air curtain, and then a humpback whale rushes out from directly below, grabbing the school of fish.

 Next, the humpback whales that have a good meal will take over their teammates to release the air curtain, and teammates will take turns preying. Sometimes, a group of whales will move together-they move up and down staggered back and forth. 

After one whale occupies the group of fish, some will always run away from the mouth, while the second whale just opens its mouth at this moment. With the cooperation of a few whales, a large school of fish was wiped out in a short while.

 

A school of herring jumping anxiously trapped by the air curtain

Humpback whale rushing into the school of fish from the bottom of the air curtain


 

Whale Hunting scene from aerial view

Air curtain fishing 

However, outside of the breeding season, many humpback whales like to move alone. How do single-headed humpback whales display such superb skills? 

In fact, it is also possible. 

Some adult whales with proficient hunting skills can complete this set of fancy performances by themselves. They will dive directly below the school of fish, allow themselves to enter the spiral, and then continue to release the air curtain, and then accelerate to rise to a full meal.

 

Schematic diagram of humpback whale spirally spreading air curtain


In fact, the method of air-curtain fishing is not unique to humpback whales. Some killer whale groups also use this method to trap their prey. Like humpback whales, some members of the killer whale group will spread an air curtain around the periphery, and other members will take turns rushing into the school to prey. However, because of the great differences in the feeding habits and predation methods of killer whales, not all killer whales have mastered this technique. 

For example, some killer whales living in Antarctic waters almost exclusively feed on seals or baleen whales. 

In the face of such prey, this air curtain predation method is ineffective, and they may have never mastered and learned this method.

 

And some small cetaceans, such as many kinds of dolphins, also fish by air curtain predation, and even derived multiple variants. Some camel dolphins living offshore, in addition to spit out bubbles to form an air curtain, some also use their tails to agitate the bottom silt to form a "silt air curtain". The predation effect is the same as the air curtain.



Author: Naval Kishore

Education: Masters Degree in Actuary

The author is an Actuarial expert with 20 Years of Work experience in Fisheries work



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