How Do Mammals Feed Underwater?

All mammals need to eat, but I was asked recently about how mammals feed underwater. While it is harder than feeding on land, many marine mammals do it.

Whales feed on large amounts of microscopic organisms. They use various techniques such as filter-feeding, bubble-net feeding, and surface feeding to catch their prey. Dolphins will eat fish and crustaceans under the water, and seals use their whiskers to help them catch fish.

If you want to know more about marine mammals feed underwater, please read on.

How Have Mammals Adapted To Feed Underwater?

Marine mammals have adapted to ear from land mammals in how they have adapted to be able to eat underwater. 

Mammals have evolved various adaptations to feed underwater, allowing them to exploit their environments for food. These adaptations can vary among different species, but they generally include:

1. Diving Abilities: Many aquatic mammals, such as seals, whales, and dolphins, have developed the ability to dive deep underwater in search of prey. They can hold their breath for extended periods and have specialized respiratory adaptations that allow them to extract oxygen efficiently from the air, even when resurfacing.
2. Streamlined Bodies: Aquatic mammals often have streamlined body shapes, reducing water resistance as they swim and hunt underwater. This shape minimizes energy expenditure during underwater pursuits.
3. Specialized Limbs or Fins: Some aquatic mammals have evolved specialized limbs or fins for propulsion and maneuverability. For example, dolphins have streamlined flippers, and seals have paddle-like limbs that enable them to swim with agility.
4. Echolocation: Many toothed whales, such as dolphins and orcas, use echolocation to locate and identify prey. They emit sound waves and listen to the echoes, allowing them to “see” underwater and track down their next meal.
5. Dietary Adaptations: Aquatic mammals have developed diets that suit their underwater environments. Some are filter feeders, like baleen whales, which use baleen plates to trap small organisms from the water. Others are carnivorous predators, hunting fish, squid, or other marine animals.
6. Blubber: Marine mammals often have a layer of blubber (thick fat) beneath their skin. This insulating layer helps regulate body temperature in cold water and provides an energy reserve for long dives and periods of fasting.
7. Salt Glands: Some marine mammals, like sea turtles and certain seals, have salt glands near their eyes or nostrils. These glands allow them to excrete excess salt from their bodies, as they may ingest seawater while feeding.
8. Thermoregulation: Aquatic mammals have mechanisms to regulate their body temperature in cold water, such as countercurrent heat exchange systems that conserve heat and prevent heat loss through extremities like flippers.

These adaptations have allowed mammals to thrive in various aquatic ecosystems, from the open ocean to freshwater rivers and lakes, by enabling them to effectively find, capture, and consume prey underwater.

Want to know how whales breastfeed underwater? I have written an article here.

Hunting Strategies

Marine mammals have several different strategies for hunting their prey. These strategies vary depending on the species, prey type, and habitat.

1. Suction Feeding: Some marine mammals, particularly beaked whales, employ suction feeding. They create a sudden and powerful vacuum to draw prey, such as squid, into their mouths. This feeding method allows them to capture prey efficiently in the deep ocean.
2. Filter Feeding: Filter-feeding marine mammals, such as baleen whales (e.g., humpback whales and blue whales), have specialized structures in their mouths called baleen plates. They swim through schools of small organisms, like krill and small fish, and then filter these prey from the water by forcing water out of their mouths through the baleen, leaving the prey behind.
3. Lunge Feeding: Some marine mammals, particularly baleen whales like humpback whales, engage in lunge feeding. This entails a rapid and forceful engulfing of large quantities of prey, such as fish or krill, by suddenly opening their mouths wide while swimming. This feeding method allows them to efficiently consume substantial amounts of prey in one engulfing motion.
4. Bubble Net Feeding: Humpback whales are known for their bubble net feeding technique. They work cooperatively in groups to blow a ring of bubbles around schools of fish, creating a barrier. This enclosure disorients and corrals the prey into a concentrated area, making it easier for the whales to swim up from below and engulf the prey with a wide-open mouth.
5. Raptorial Feeding: Many marine mammals, such as dolphins, orcas, and seals, are fast and agile swimmers. They use pursuit predation, which involves actively chasing and capturing prey. These animals rely on their speed, sharp teeth, and cooperative hunting tactics to catch fish, squid, and other fast-moving prey.

Suction Feeding

Marine mammals have learned to adapt to their environment by sucking food and water in, They then use 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. 

Beaked whales are the most well-known suction feeders.

1. Suction Cups: Beaked whales have unique mouths with a flexible lower jaw that can expand to create a large cavity. Inside this cavity, the tongue forms a piston-like structure, and the roof of the mouth has small suction cups. When a beaked whale encounters prey, it rapidly expands its mouth cavity and then closes it quickly, creating suction. This action helps draw prey, such as squid and fish, into the mouth.
2. Prey Capture: Beaked whales primarily feed on deep-sea squid and other cephalopods. They use suction feeding to capture prey at significant depths, where the pressure is high and the visibility is low.
3. Rapid Feeding: Suction feeding allows beaked whales to capture prey quickly and efficiently in the deep ocean. This is particularly important because it minimizes the time they spend near the surface, where they are vulnerable to predation by sharks and orcas.

Other animals that use the suction-feeding strategy include some species of seals and sperm whales. These mammals do not use their teeth but will suck the prey directly into their mouth. They can do this from a distance by manipulating the water in front of them and can scoop up prey from the seafloor in the same way.

Do whales drink seawater? Find out here.

Filter Feeding

Another adaptation that some marine mammals use is a filter system in the mouth. Baleen whales, such as the gray whale, have an elaborate baleen plate system. Instead of teeth, the baleen plate is shaped like a comb and acts as a sieve.  

Baleen whales suck in large amounts of food at once, swimming with their mouths open. The food will get caught on the baleen plate’s bristles while the water passes through before being expelled. 

Baleen whales can catch thousands of tiny animals on the bristles, including krill, fish, crustaceans, and shrimp. They then swallow the food into their mouth using their tongue. 

Rorqual whales like blue and humpback whales use a slightly different system. They maintain a specialized filter system but do not use the same suction system. 

They filter small prey directly from large mouthfuls of seawater underwater and take in food without ingesting seawater. They gulp in the seawater and then push the water through the baleen plates. 

This leaves their diet of krill, fish, and crustaceans on the inside of the plate, allowing them to use their tongue to take them to the stomach. Using the system, they can feed on larger, faster fish such as herrings and sardines.

Lunge Feeding

Some marine mammals use lunge feeding to catch their prey. Rorqual whales such as blue whales use this system to feed on large quantities of fish. Lunge feeding occurs 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, as 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.

Raptorial Feeding

Many marine mammals use raptorial feeding methods underwater. Dolphins and seals commonly use this method despite having mouths full of razor-sharp teeth.

Raptorial feeding in whales refers to a feeding strategy where a whale actively hunts and captures prey, typically larger or more agile prey, using its physical abilities, such as speed, agility, and powerful jaws. This type of feeding is in contrast to filter feeding, where whales strain small prey from water or sediment.

Raptorial feeding is most commonly associated with toothed whales, which have sharp teeth and a carnivorous diet. These whales are often predators that actively pursue and capture their prey.

Raptorial feeding also allows large sea mammals, such as blue whales, to feed in the deeper parts of the ocean without suffocating and starving.

Other notable raptorial feeders include:

1. Orca (Killer Whale): Orcas are well-known for their raptorial feeding strategies. They are apex predators and hunt a variety of prey, including fish, seals, sea lions, and even other whales. Orcas work together in pods to coordinate their attacks on larger prey, using their intelligence and teamwork to subdue and consume their quarry.
2. Sperm Whale: Sperm whales are known to be deep divers, and they often target large prey like giant squid in the depths of the ocean. They use their powerful jaws and teeth to capture and consume these elusive prey items.
3. False Killer Whale: False killer whales are known for their aggressive and raptorial feeding behavior. They feed on a variety of prey, including fish and squid, and may use coordinated tactics to surround and capture their prey.
4. Pygmy Killer Whale: These smaller toothed whales are also known for their raptorial feeding habits, targeting fish, squid, and other small marine organisms.

Bubble Net Feeding

Humpback whales and Bryde’s whales have a unique way of feeding called bubble net feeding. This is only done by these two species of whales.

Bubble net feeding is done in groups, with group sizes ranging between a minimum of two or three and a maximum of sixty whales. In most cases, bubble-net feeding is completed in small groups.

Bubble net feeding is used to capture and concentrate prey, typically small schooling fish or krill, into a confined area, making it easier to engulf large quantities of prey in a single mouthful.

Bubble net feeding is a complex, highly synchronized effort, which shows high biological intelligence. Bubble net feeding is a method that is not instinctual but learned, as not all humpback populations worldwide know how to use the method.

Here’s how bubble net feeding works:

1. Group Coordination: Bubble net feeding is often a cooperative group effort among humpback whales. Whales use vocalizations to communicate with one another.  One of the whales leads the behavior by diving deep and then rising to the surface. 
2. Bubble Generation: A group of humpback whales begins by diving beneath a school of prey. One or more of the whales in the group exhales forcefully, releasing a stream of bubbles in a circular or spiral pattern as they swim in an ascending spiral path toward the surface. These bubbles rise and create a cylindrical or net-like structure underwater.
3. Prey Enclosure: As the bubbles rise, they form a barrier that encircles the school of prey. The wall of bubbles disorients and confines the prey within the cylinder, making it difficult for the fish or krill to escape. The bubbles produce a loud and intense sound that alerts other whales to feed. 
4. Coordinated Ascent: While the prey is concentrated within the bubble net, the humpback whales swim upward in a coordinated manner, staying beneath the prey. They surface with their mouths wide open, engulfing both prey and water.
5. Filtering Out Water: Once at the surface, the humpback whales close their mouths and push out the excess water through their baleen plates, which act as a filter. The prey items, such as fish and krill, are trapped on the inside of the baleen plates and can be easily swallowed.
6. Repeat Process: Humpback whales may perform this bubble net feeding behavior multiple times during a single feeding event, increasing their chances of capturing a substantial amount of prey.

Ever wondered why whales breach? Find out here

How Do Baleen Whales Differ From Toothed Whales In Eating Habits?

It is estimated that about 86 species of whales, dolphins, and porpoises are in the world’s oceans. They are categorized into two main categories Mysticetes (baleen whales) and Odontocetes (toothed whales). 

Both of these categories exhibit distinct body morphologies. There is a significant contrast between whales with teeth and those without, reflecting variations in their dietary habits and feeding methods.

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’s mouth, and the whale then swallows.

Toothed whales eat large prey like fish, squid, birds, and even marine mammals as big as seals. They eat using their teeth to latch onto their prey and bite it into small pieces. They do not take in large amounts of seawater when feeding.

Want to know more about how baleen whales eat? I have written this article which you may find interesting.

How Do Dolphins Eat?

Dolphins are toothed whales known for their diverse and dynamic feeding behaviors. They use a combination of techniques to capture and consume prey, which can include fish, squid, and other marine organisms.

Dolphins are skilled hunters with a diverse diet, although they primarily feed on fish. Their ability to locate and capture prey in aquatic environments is facilitated by a set of remarkable adaptations. One of their most impressive tools is echolocation.

Dolphins emit high-frequency clicks or sounds, which bounce off objects and return as echoes. By interpreting these echoes, dolphins can essentially create detailed “sonar images” of their surroundings. This sophisticated sensory system allows them to pinpoint the location of prey with remarkable precision, even in murky or dark waters.

In addition to echolocation, dolphins have specialized sensory whiskers, known as vibrissae, around their mouths. These vibrissae are highly sensitive and enable dolphins to detect subtle movements of prey in the water, particularly when visibility is limited. Dolphins are also renowned for their speed and agility in the water. They use their exceptional speed to pursue schools of fish and their agility to navigate through them during the hunt.

Cooperative hunting is a strategy employed by some dolphin species. They work together in groups to corral and concentrate schools of fish, making it easier to capture their prey. While fish are a primary component of their diet, dolphins are opportunistic feeders and also consume squid, crustaceans, and other marine organisms. The specific prey species can vary depending on the dolphin’s geographic location and habitat.

Feeding techniques among dolphins include chasing and herding, where they actively chase and corral schools of fish, using their bodies to create a barrier that confines the prey. Dolphins are also known for their quick strikes, using their sharp teeth to make rapid captures. This combination of sensory adaptations and hunting strategies allows dolphins to efficiently locate, pursue, and capture prey in their underwater world.

1. Chasing and Capturing: Dolphins are agile swimmers and often engage in active pursuit of prey. They may swim in coordinated groups called pods to encircle schools of fish or other prey items. Using their speed and maneuverability, they chase and corral the prey into tighter groups.
2. Using Echolocation: Dolphins have a highly developed echolocation system, which allows them to emit high-frequency sounds (clicks) and interpret the echoes to “see” their surroundings, including prey. This sensory adaptation helps them detect and locate prey, even in dark or murky waters.
3. Herding and Coordinated Hunting: Dolphins may work together in coordinated hunting strategies. In some cases, they encircle prey from below or use their bodies to create a barrier, forcing prey to move closer to the surface where they can be more easily captured.
4. Snatching Prey: Once prey is within reach, dolphins can use their sharp teeth to snatch individual fish or squid from the school. They may stun or immobilize prey with rapid headshakes or slaps of their tails.
5. Swallowing Whole: Dolphins typically swallow prey whole, as their teeth are designed for capturing and grasping rather than chewing. Larger prey items are often broken into smaller pieces or manipulated to be more easily swallowed.
6. Group Feeding: Dolphins often share their catch with other pod members, reinforcing social bonds within the group. They may also cooperate to access hard-to-reach prey, such as fish hiding in crevices.
7. Feeding on the Go: Dolphins often feed while swimming, which means they may capture prey while in motion. This behavior allows them to maintain their energy levels throughout the day.
8. Variety in Diet: The diet of dolphins varies depending on their species and habitat. Some primarily feed on fish, while others specialize in squid or a combination of prey types.

It’s important to note that different species of dolphins have unique feeding strategies and preferences based on their size, geographic range, and available prey. Dolphins are opportunistic feeders, adapting their hunting techniques to the specific conditions and prey species they encounter in their respective environments.

How Do Seals Eat?

Seals are marine mammals known for their diverse feeding habits and adaptability to various aquatic environments.

The diet of a seal consists mainly of fish. They use their whiskers to locate prey, specifically in cloudy water. Seals are entirely adapted to life underwater and can feel the slightest movement in the water. 

Seals use this ability to “see” in turbulent waters and find where the fish are. They can sense the slightest movements up to a distance of up to 100 meters. Seals can also determine the fish’s size and shape at that distance from their movement. 

Seals are not selective on the prey they catch and eat, although the fish they eat does vary per season.

Seals forage mainly in shallow coastal waters, close to the seabed. Seals dive for just a few minutes, swallowing their prey whole underwater. 

Seals 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 eat it again to eliminate any excess sand and water consumed. 

1. Foraging Techniques: Seals employ several foraging techniques to capture prey, including the following:
   • Ambush Predation: Some seals, like leopard seals and Weddell seals, are known for their ambush predation. They wait near the water’s edge or under the ice, striking quickly at prey as it enters the water.
   • Pursuit Predation: Other seals, such as harbor seals and common seals, are agile swimmers and use pursuit predation. They actively chase and capture prey, which may include fish, squid, and various marine invertebrates.
   • Filter Feeding: Certain seal species, like the crabeater seal, are filter feeders. They use specialized teeth to filter krill and other small prey from the water, often in dense swarms or schools.
2. Diet Diversity: Seal diets can vary widely. Some seals are specialized feeders, primarily consuming a single type of prey, while others have a more varied diet. For example, leopard seals primarily eat penguins and other seals, while harbor seals often consume a variety of fish and invertebrates.
3. Hunting Depth: Seals are capable of diving to varying depths to locate prey. Some, like elephant seals, can make deep dives to find squid and fish in the open ocean, while others, like ringed seals, may hunt in shallower waters under ice sheets.
4. Strategic Breathing: Seals have adapted to control their breathing while hunting underwater. They can hold their breath for extended periods, often relying on oxygen stored in their muscles and blood to sustain them during dives.
5. Feeding and Fasting Cycles: Many seal species have feeding and fasting cycles that align with breeding and molting seasons. During the feeding season, they accumulate body fat to sustain them during times when they are not actively hunting or are on land for breeding or molting.
6. Sharing Prey: In some seal colonies, there may be competition for limited resources. Dominant individuals may claim larger shares of the prey, while subordinates receive smaller portions or feed on less preferred prey items.
7. Underwater Vision: Seals have excellent underwater vision, which allows them to spot prey even in dimly lit or turbid waters. Their ability to see well underwater is an advantage in locating and capturing prey.
8. Social Feeding: Some seals may engage in social feeding behaviors, where several individuals work together to corral or concentrate prey. This cooperative hunting strategy can improve their chances of capturing prey, especially when hunting in groups.

Seals are opportunistic feeders and have evolved a variety of feeding behaviors to adapt to their specific ecological niches and prey availability in their habitats. Their feeding strategies are influenced by their environment and the types of prey they encounter.

References And Further Reading

Marine Mammals: Evolutionary Biology by Annalisa Berta, James L. Sumich, and Kit M. Kovacs

This comprehensive book covers various aspects of marine mammals, including their feeding behaviors and adaptations. It offers a scientific perspective on the subject.

Marine Mammal Biology: An Evolutionary Approach by A. Rus Hoelzel

This book explores the biology of marine mammals, including feeding strategies and dietary ecology. It discusses the evolutionary aspects of their feeding behaviors.

Marine Mammal Physiology: Requisites for Ocean Living by William A. Walker, Bernd Würsig, and Thomas M. Williams

This book delves into the physiological adaptations of marine mammals, which are often related to their feeding and foraging strategies.

Whales, Dolphins, and Porpoises: A Natural History and Species Guide by Annalisa Berta

This field guide provides insights into the natural history of various marine mammals, including their feeding habits, diet, and foraging behaviors.

Biology of Marine Mammals by John E. Reynolds III, Sentiel A. Rommel, and Douglas Wartzok

This book covers a wide range of topics related to marine mammals, including feeding ecology, sensory adaptations, and the mechanics of feeding.

Marine Mammal Sensory Systems edited by Joseph Thomas and Daniel K. Odell

While primarily focused on sensory systems, this book discusses how the sensory adaptations of marine mammals are linked to their feeding behaviors and ecological roles.