All mammals need to eat, but I was thinking the other day about marine mammals and the many different ways they have adapted.
Marine mammals catch their food in many ways. Whales feed on large amounts of microscopic organisms. They use various techniques such as filter-feeding, bubble-net feeding, and surface feeding to catch these. Dolphins will catch and eat fish and crustaceans under the water, and seals use their whiskers to help them catch fish.
How Have Mammals Adapted to eat Underwater?
Marine mammals differ from land mammals in how they have adapted to be able to eat underwater. Although they can swim, a dog would not be able to get the water and be able to eat.
Whales, dolphins, seals, and other marine mammals can eat underwater, which is due to how they have made several changes to their feeding strategies.
Marine mammals feed entirely underwater. Seals and dolphins can hunt, catch, and swallow food beneath the water. Marine mammals make sure that they capture their prey and not swim away before swallowing. They do this by sucking the food deeper into the mouth by pulling back their tongue once the prey is in their mouth.
Marine mammals have learned to adapt to their environment by sucking food in, using their tongues to ensure the fish or other food types are in their mouth. They take advantage of this ability to suck their prey in by manipulating the water flow in front of their mouths. Their mouth becomes a suction feeder to ensure their prey does not escape.
Some of the animals that use suction feeding strategy include some species of seals, sperm whales, and beaked whales. These types of mammals do not use their teeth but will hoover the prey directly into their mouth.
They can do this from a distance by manipulating the water in front of them and even from the seafloor.
Another adaptation is that some marine mammals use a filter system. Filter feeders can use their specialized filtering abilities to feed. Baleen whales such as the gray whale have an elaborate plate system. Instead of teeth, the baleen plate is shaped like a comb, which acts as a sieve.
Baleen whales can take in large amounts of food at once, swimming up to feed with its mouth open. The food will get caught on the bristles of the baleen plate while the water will pass through.
Baleen whales will catch thousands of tiny animals, including krill, fish, crustaceans, and shrimp on the bristles. They then bring the food into their mouth with their tongue.
Rorquals like the blue whale and humpback whales are also baleen whales but use a different system. They maintain a specialized filter system but do not use the same system of suction.
They have the ability to filter small prey directly from large mouthfuls of seawater while underwater and take in the prey only without ingesting seawater. They gulp in the seawater but then push the water out through the baleen plates. They push the water out with the tongue.
This leaves their diet of krill, fish, and crustaceans on the inside of the plate, allowing them to use their tongue to take them down. By using the system, they can feed on larger fish such as herrings and sardines.
Some marine mammals use a system of lunge feeding. Rorqual whales such as the humpback whale and blue whale use this system to feed on large fish quantities. Lunge feeding happens when a whale increases its speed to a high velocity, opening its mouth to a large gape.
This allows them to take in large amounts of seawater as they swim. This water passes through their filters and provides them with plenty of food.
Rorquals are the only whales that can use this method of lunge feeding. They have features that no other whales have. These include throat pleats that can expand, separate mandibles, and a set of nerves that can stretch and recoil.
Marine mammals use raptorial feeding methods underwater. Dolphins and seals commonly use this despite having mouths full of razor-sharp teeth.
The unique skill of how dolphins and seals hunt is that they can swallow their prey while still underwater. This enables them to hunt without returning to the surface.
These underwater eating strategies enable marine mammals to access all the food sources available in the sea. Raptorial feeding also allows large sea mammals such as blue whales to live in the sea without suffocating and starving.
Bubble Net Feeding
Humpback whales and Bryde’s whales have a unique way of feeding referred to as bubble net feeding. This is a very unique and complex feeding behavior only done by these two species of whales.
Bubble net feeding is done in groups, with group sizes ranging in between a minimum of two or three and a maximum of up to sixty whales. In most cases, bubble-net feeding is completed most of the time in small groups.
Humpback whales are migratory whales and only concentrate on eating during half of the year. Typically, they will spend their summer months in feeding grounds.
Most of this time, they can be found in southeast Alaska. The other half of the year, they spend the time in their breeding grounds, where they hardly eat at all.
When it’s the season to eat, humpback whales actively feed up to twenty-two hours a day. They consume a lot of food, storing the excess as fat to use throughout the breeding season.
Bubble net feeding is a complex, highly synchronized effort, which shows these species have high biological intelligence. Bubble net feeding is a method of feeding that is not instinctual but learned.
According to some studies, not all humpback populations worldwide know how to use the bubble net feeding method.
To feed in this way, humpback whales start to use vocalizations to communicate with one another. One of the whales leads the behavior by diving deep then rising to the surface.
Starting from deep in the sea, they begin to blow air to the surface, creating bubbles. The bubbles are used as a way to confuse and trap the fish above. Other whales circling the fish will also blow bubbles.
Meanwhile, the rest of the humpback whales will make a circle to create a cumulative fence around the prey. Once the fish are inside the circle, the bubbles will stop them from escaping.
In creating bubbles, the humpback whales produce a loud and intense sound that assists in the process, advising other whales to feed. The whales will simultaneously swim up to the surface to feed on the fish trapped in the bubbles. It is teamwork that makes the process easier.
Other times humpback whales swim in a shrinking circle as they blow bubbles. Together they can force the fish towards the surface. This causes a trap, with the fish not able to break out of the bubbles.
How do Baleen Whales Differ From Toothed Whales in Eating Habits?
It is estimated that there are about 86 species of whales, dolphins, and porpoises in the world’s waters. They are categorized into two main categories Mysticetes (baleen whales) and Odontocetes (toothed whale).
Both of these categories have specific body morphology. There is a huge difference between whales with teeth and whales without. This also shows a difference between what each eats and how.
Baleen whales eat by taking a large amount of water underwater into their mouths, shutting their mouths, and moving their tongue up to the roof of their mouth, which forces all the water out through the baleen.
The baleen acts as a filter, trapping food such as krill in the whale mouth, and the whale then swallows.
On the other hand, toothed whales eat large prey like fish, squid, birds, and even marine mammals like seals. They eat using their teeth to latch onto their prey and subsequently bite it into small pieces. They do not take in the seawater.
How Do Seals Eat?
The diet of a seal is generally just fish. They use their whiskers for locating prey, specifically in cloudy water. Seals are entirely adapted to life underwater and have the ability to feel the slightest movements in the water.
Seals use this ability to “see” in turbulent waters and to find where the fish are. They use this sense of feeling the slightest movements up to an estimated distance of up to 100 meters. Seals also have the ability to determine the size and shape of the fish at that distance.
Seals are not selective on the prey they catch and eat, although what they eat does vary per season, depending upon what food is available.
Mostly, seals forage in shallow coastal waters, usually on the seabed. However, they will occasionally feed in mid-water. Seals dive for just a few minutes, swallowing their prey whole underwater.
They will also bring larger catches up to the surface. Once they are on the surface, they shake and bite them into smaller pieces before swallowing. Seals often regurgitate prey underwater and immediately swallow it again to get rid of any excess sand and water consumed.