In Juneau, Alaska, a group of us chartered a whale watching boat for the afternoon to head out into the Pacific Ocean off the coast of Juneau to look for the humpback whales that eat all summer in the cold waters full of salmon, krill (small shrimp) and herring, before migrating back to their mating grounds in Hawaii (90% of the whales around Juneau) or Mexico (10% of the whales). It was a cool, rainy day that was overcast, misty and damp. Not the most pleasant weather, but the whales put on their swimming and eating show for us, none-the-less…
We found a pod of humpback whales and were able (by law) to stay a couple of hundred yards (meters) away and watch for 30 minutes. In the middle of our watch, we were quite fortunate in observing the rare bubble-net feeding where a group (here about a dozen) of humpback whales work together to create a net of bubbles that “traps” the fishes. Collectively the fishes then rise to the surface and swallow literally tons of sea water and fishes (filtering out the water with their unique baleen plates). It’s quite a spectacle to watch (see photographs, below). Our guide told us that in three months of sailing daily (one or two trips per day), this was only his seventh observation this season of bubble-net feeding. We left feeling quite lucky!
“Bubble-net feeding is a unique and complex feeding behavior engaged in by humpback whales (Megaptera novaeangliae)… It is one of the few surface feeding behaviors that humpback whales are known to engage in. This type of feeding is often done in groups. The group size can range from a minimum of two or three whales participating and up to sixty at one time. Whales can also perform a similar method of surface feeding called lunge feeding but is done solo.
“Humpback whales are migratory and only eat during half the year. They will typically spend the summer months (May through September) in feeding grounds with cooler waters that they return to every year. They have been documented feeding in areas such as Southeast Alaska and off the coast of Antarctica. During the other half of the year humpbacks will spend time in their breeding grounds where they do not eat at all. During their feeding season humpback whales will actively feed for up to twenty-two hours a day. They do this in order to have enough fat reserves stored in their bodies to live off of during their breeding season.
“Bubble-net feeding is a cooperative feeding method used by groups of humpback whales. This behavior is not instinctual, it is learned. Not every population of humpbacks know how to bubble net feed according to some studies. After observing different populations it is apparent which whales know how to create a bubble net and which do not. They have to learn the method in order to be successful. Humpback whales use vocalizations to communicate to one another in order to effectively and efficiently execute the bubble net in order for them all to feed. As the group circles a school of small fish such as salmon, krill [small shrimp] or herring they use a team effort to disorient and corral the fish into a net of bubbles. One whale will typically begin to exhale out of their blowhole beneath the surface at the school of fish to begin the process. More whales will also start to blow bubbles while continuing to circle their prey. They corral the fish into a tight circle while creating a net of bubbles to surround the fish and keep them from escaping. The size of the net created can range from three to thirty meters in diameter. One whale will sound a feeding call, at which point all whales simultaneously swim upwards with mouths open to feed on the trapped fish. As the whales swim up to the surface to feed they can hold up to 15,000 gallons of sea water as they use their baleen plates to strain the water to get the maximum amount of fish they need. Humpback whales have 14 to 35 throat grooves that run from the top of the chin all the way down to the navel. These grooves allow the mouth to expand. When they swallow they blow the sea water out from their blowhole as they ingest the fish. The fish that they ingest are also a source of hydration for them. Bubble netting is an advanced and necessary feeding method developed by humpback whales to feed multiple mouths at one time.” — Wikipedia
Humpback Whales of Alaska
“The humpback whale got its name due to the fact that the dorsal fin sits on a big hump on the whales back which is visible when the whale arches its back and dives.
“Humpback whales can be found in the Bering Sea, Aleutian Islands, Prince William Sound, Glacier Bay and throughout the Inside Passage of South East Alaska in the summer. In the winter they move south to the Banderas Bay in Mexico, Baja California and the Hawaiian islands. They spend the spring, summer and fall months in the cooler waters around Alaska and head for warmer waters in the winter months. Researchers believe that there may be resident populations in the southeastern part of the state.
“Their diet consists of krill and many different kinds of fish including chovies, sardines, herring and capelin. They gather their food by blowing a net of bubbles to surround and confuse their prey, then with jaws open swim through the center of the air ring to scoop up their food. Baleen, finger like material, hangs down in the whale’s mouth to filter the food from the water. They eat one to one and a half tons of food a day. During winter months they don’t feed but live off fat reserves in their blubber.
“They are easily identified by the distinct hump in front of their dorsal fin. They have the largest scalloped, winglike flippers of any whale species. They are mostly black with a white area on their throat. The flippers are all white beneath and partly white above. They are unusually susceptible to parasites resulting in there being up to a half a ton of barnacles on a single whale.
“Humpbacks can be found in groups of four to five but generally travel and feed individually. They are relatively slow swimmers with speeds up to 16 miles per hour with and average speed of 2-9 miles per hour. In the summer they dive for 3-5 minutes but in the winter breeding grounds can dive for 15-30 minutes.
“Humpback whales breech, throwing themselves completely out of the water. You may also see them swimming on their back with both flippers in the air. They are known for tail lobbing, raising its huge fluke out of the water and slapping it on the water surface. Researchers believe this is a form of communication as the slaps can be heard for long distances underwater.
Humpback whales have the most diverse range of sounds for any whale or animal in the world. Sounds include moans, shrieks and grunts. Males sing for 10-20 minutes to attract a mate, repeating the sequence for hours during winter breeding months. Their feeding song is high-pitched which stuns fish causing them to stop swimming long enough for the humpback to gobble them up.
“The humpback whales’ main predator is the killer whale. Commercial whalers were allowed to hunt humpbacks into the 20th century. Today as whales live so close to the coastlines they are often hurt by pollution, collision with boats and getting tangled in fishing nets. But this is why new rules have been created to protect the mammals of our oceans. You will find that tour boats must maintain a safe viewing distance to protect the whales.” – www.whale-watching-alaska.com
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