I was recently asked about baleen whales and their techniques for collecting food.
There are three families of baleen whales, and all three use different techniques to feed. Right whales and bowhead whale use filter feeding, gray whales use a bottom-feeding approach, and rorquals use bubble net feeding, gulp feeding, and circle feeding.
How Do Whales Use Baleen?
Baleen whales have a row of triangular plates closely packed together, hanging from each side of the mouth’s roof. The leaves are made from the same material as our human fingernails, keratin. There are up to 400 baleen plates in the mouth, and they have a hairy fringe on the inside.
Baleen whales use a method of filter-feeding to take in large quantities of water and food simultaneously. The fringes overlap inside, which forms a mat through which the baleen whales feed. They filter water through the carpet, straining any food from the water.
The whales use their tongue to sweep the food from the baleen mat down into the throat. This wears the baleen fibers down, although these grow back, much like our fingernails.
Bowhead Whale, North Atlantic Right Whale, North Pacific Right Whale, Southern Right Whale
The bowhead whale, the North Atlantic right whale, the North Pacific right whale, and the Southern right whale all feed similarly. As members of the Balaenidae family, all four whale species have long baleen plates, which provide an area large enough to pass the water through.
The plates can be up to 4 meters long in bowhead whales and up to 2.7 meters in other whales. The shape of the jaw and lips of these whales is due to the baleen. The form allows them to scoop up water while swimming slowly forward.
The fibers on the baleen catch tiny plankton. Unlike other baleen whales, the fibers are fine, allowing them to see organisms as small as 2.5mm long.
Right whales are masters of skim feeding. Right whales swim forward with their mouths open, allowing the water to pass through the mouth and out the baleen plates.
These plates, which are at the sides, allow their food to be caught. They will then use their tongues to remove the organisms and push them into their digestive systems.
Skim feeding is generally done at the water’s surface, and right whales can be seen with just their upper jaw out of the water. However, they will also feed at different depths in the sea, including near the seabed.
The skim feeding technique also plays a large part in the whales’ shape and body differences. Unlike other ways of feeding, there is no need for the throat to expand, and the large pleats called ventral grooves seen on other whales’ familiesales are absent.
As the whale swims forward, their mouths are partly open. The water streams out from the inside through the baleen plates, whereas in other families of whales, large amounts of water need to be expelled. Right whales have long baleen, causing the mouth to be arched.
Blue Whale, Bryde’s Whale, Fin Whale, Minke Whale, Sei Whale, Humpback Whale
Members of this family, rorquals, have a unique anatomy that allows them to feed. All family members have an elastic, pleated tissue that runs along their underside, from the lower jaw to the umbilicus: these wrinkles, or grooves, range from fifty in sei whales to ninety in blue whales.
Rorquals use a technique called gulp feeding. The whales take in vast amounts of water before closing their mouths and expelling the water through the baleen. Rorquals have smaller heads with shorter baleen plates.
Rorquals can take in large amounts of prey faster than right whales over a shorter time.
The baleen expands when feeding, and the jaw can be opened very big to allow large amounts of water and food to enter. Rorqual whales have a tissue at the sides of their jaw, which is elastic, allowing the jaw to open up to 90 degrees vast.
The pleated throat allows rorquals to expand the throat like a concertina. This will enable them to increase the capacity in their mouths when feeding. Many tonnes of seawater are filtered in every mouthful.
The whale lunges forward to capture water and food before forcing the water out in two ways. They let the water out through the gap between the sides of the top and bottom jaws. They also squeeze the water through the baleen plates on their underside.
Any organisms captured in the mouth are then pushed down the throat and swallowed. They usually use their tongues to take the food off their teeth and down their throat. Due to the size of the whale, their languages are equally significant. Their tongues have a rough texture and cover the entire floor of their mouth.
Blue, fin, and humpback whales all feed using gulps. All three whales are large, and due to their size, they need larger prey.
Being larger, their baleen fibers are also more coarse. This allows them to eat larger prey, such as fish and crustaceans.
Sei whales have particular adaptations that make them the only rorquals that use skim feeding regularly. Sei whales use this technique due to much finer baleen fibers than other rorquals. The fibers allow them to swim forward with their jaws open at a narrower angle, allowing them to capture much smaller organisms.
Rorquals use many techniques to catch their prey. Humpback whales use a mechanism called bubble net feeding.
Bubbles are made underwater by whales and float to the surface. The whales can release these bubbles in a straight line, called a curtain.
The bubbles rise to the surface, and fish and other prey will not usually pass through or around these bubbles. This allows the whale to feed in a straight line along the ‘curtain’ to swallow all the fish.
In the case of bubble-net feeding, the whales will swim around in a circle, releasing the bubbles underwater. The fish get caught in the ‘net when the bubbles reach the surface.’ Fish and krill can be seen jumping in the center of the circle of bubbles before the whale comes crashing through the water’s surface with its mouth open, eating everything inside the bubbles.
Humpback whales can carry out this feeding on their own, but unusually for whales, they can also use bubble net feeding in larger groups. Sometimes humpback whales will pair up to feed, but groups of 24 have been noted, with some feeding together year after year.
Fin whales have different types of feeding techniques that they use. Fin whales swim on their sides in a circle. When looking at a fin whale, if all you can see is one-half of the tail fluke, they are likely feeding.
Fin whales are white on the sides of their heads, and it is thought that the white confuses and scares the fish and plankton to the surface. When at the surface, fin whales propel themselves forward to gulp down the prey.
Whereas right whales have a very arched mouth, gray whales have a much smaller arch. This allows the baleen to be much shorter and coarser.
Gray whales have throat pleats, but where rorquals have between twenty and ninety wrinkles, the gray whale only has one or two pairs on rare occasions.
The gray whale is unique among baleen whales in the way it feeds. Rorquals and right whales feed at the water’s surface; gray whales do not.
Gray whales collect their food from just above the ocean floor or the mud layer on the ocean floor.
When looking at gray whales, it is noticeable that the short, coarse baleen on one of their sides is much more worn than on the other. This allowed researchers to discover that gray whales forage while on their side.
Gray whales disturb the seafloor’s mud, stirring it up using their snout to bring invertebrates out of the earth. Gray whales also press their tongue against the bottom of their mouth, causing suction through their mouths. By drawing in the water this way, they can force it out again through the baleen. Any mud taken in is pushed back through the baleen with the tongue.
Although it was initially thought that all gray whales fed on their right side, this has proven false. The absence of barnacles on the left side of some gray whales proves that some are ‘lefties.’ The whales, when feeding, rub the barnacles off against the ocean floor.
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