15 Animals That Eat Seaweed in the Wild

Have you ever wondered which creatures snack on seaweed beneath the waves?

While seaweed may look like nothing more than ocean plants waving in the water, it actually plays a big part in many animals’ diets.

Many marine animals, such as crabs, sea urchins, shrimp, some fish, and even certain sea turtles, eat seaweed as a key source of food What Eats Seaweed?.

Learning about animals that eat seaweed gives a deeper look at ocean food chains and how different species survive.

Readers will discover not only which animals rely on seaweed, but also how this simple food supports entire communities underwater.

This article invites everyone to explore the hidden relationships in the ocean that keep life going beneath the surface.

1. Sea Urchins

Sea urchins are small, spiny animals that live on the ocean floor.

They play an important role in keeping the ocean ecosystem healthy.

These creatures are known for being strong eaters of seaweed, especially different types of algae.

Their favorite foods include kelp and other types of marine plants.

Sea urchins use their mouthparts, which look like tiny jaws, to scrape and chew these plants from rocks and coral.

Diet of Sea Urchins:

Most sea urchins are omnivores, meaning they eat both plants and some small animals.

While their main food is seaweed, they may also eat slow-moving animals like sponges and crinoids if they find them.

They use their tube feet to move and to help grab food like drifting kelp.

Sea urchins are found in oceans around the world, from shallow reefs to deep sea floors.

In places like Hawaii, their eating habits help control invasive seaweed, which gives native coral and fish more space to grow.

You can read more about how sea urchins control seaweed populations at the Hawaii Division of Aquatic Resources site.

Because of their love for seaweed, sea urchins are often called the “vacuum cleaners” of the ocean.

They help keep ocean plants in balance and support healthy habitats for other sea creatures.

For more about their eating habits, visit this NHM page on sea urchins.

2. Parrotfish

Parrotfish are colorful reef fish found in tropical oceans. They play an important role in ocean ecosystems by eating algae and seaweed that grow on coral reefs.

Their strong beaks let them scrape algae from rocks and coral.

Most parrotfish are herbivores. They mainly eat seaweed and other plant matter, using their teeth to grind it down.

This helps keep coral reefs healthy, as too much seaweed can smother young corals.

Parrotfish are considered a keystone species because of their effect on reef balance.

Key facts about parrotfish and seaweed:

Parrotfish have an interesting way of feeding. They take about 20 bites each minute as they graze on coral and rocks to find algae and seaweed.

Some species also eat small invertebrates, but most of their diet comes from plant material.

By eating seaweed, parrotfish help clean the reef and make space for coral to grow.

Without them, coral reefs would have much more seaweed and less healthy coral communities.

Their eating habits even create sand as they grind up bits of rock and coral while feeding.

This sand ends up on beaches. You can learn more about their role in sand production at the Monterey Bay Aquarium page on parrotfish.

3. Surgeonfish / Tangs

Surgeonfish and tangs are common fish found in coral reefs.

They belong to the family Acanthuridae, which has about 86 species.

These fish are known for their bright colors and unique body shapes.

Most surgeonfish and tangs eat seaweed and different kinds of algae.

Their small mouths and sharp teeth help them scrape and graze algae off rocks and coral.

This feeding behavior helps keep the reef clean by controlling the growth of algae.

Some species may also eat zooplankton, but algae and seaweed are their main foods.

Here is a quick overview:

Surgeonfish are important for coral reefs. By eating algae and seaweed, they help the coral breathe and get enough sunlight.

Without these fish, algae could grow too fast and smother the coral.

For example, the blue tang is a well-known type of surgeonfish.

Like many of its relatives, the blue tang spends most of its time grazing for algae and seaweed.

You can read more about the habits of surgeonfish and tangs at the Waikiki Aquarium.

Many people keep tangs as pets in saltwater aquariums. In home tanks, they should be given seaweed or algae sheets to match their natural diet.

Surgeonfish add color and help balance the ecosystem in both wild reefs and aquariums.

4. Green Sea Turtles

Green sea turtles are large marine reptiles known for their plant-based diet.

Unlike many other sea turtles, adults eat mostly seaweed and seagrass.

Young green sea turtles start out eating small animals like jellyfish and insects.

As they grow, their diet shifts to marine plants. Common foods include sea lettuce, red algae, and crinkle grass.

Their beaks are finely serrated, allowing them to easily tear and chew tough plants.

This special beak helps them scrape algae off rocks and break apart grasses.

Example foods for green sea turtles:

Eating these marine plants not only gives the turtles energy but also helps keep underwater plants healthy by controlling their growth.

Green sea turtles live in warm oceans around the world and can often be seen grazing on seaweed and seagrass.

Because they depend on seaweed and seagrass, green sea turtles are sensitive to changes in their habitat.

Pollution and damage to seagrass beds can make it hard for them to find food.

Protecting their feeding grounds is important for their survival.

5. Manatees

Manatees are gentle, slow-moving mammals that live in shallow rivers and coastal waters.

People often call them “sea cows” because of their large size and grazing habits.

These animals are plant-eaters, or herbivores. Manatees spend many hours eating underwater plants each day.

Their favorite foods include seagrasses, weeds, and even algae.

They will also munch on over 60 different plant species found in their environment.

Manatees do not just eat plants from the sea. If they find other types of vegetation, such as mangrove leaves or floating plants, they will eat those too.

Sometimes, they may graze on algae from rocks or boat hulls when it’s easy to reach.

Manatee Diet Table

Manatees require large amounts of food due to their size. They can eat up to 10% of their body weight in a single day.

Most of their time is spent searching for and eating seaweed and other aquatic plants.

You can learn more about manatees’ eating habits at the Florida Fish and Wildlife Conservation Commission’s page on Florida manatee facts.

6. Abalone

Abalone are sea snails that spend most of their lives attached to rocks in coastal waters.

These creatures have a hard, rounded shell and a strong foot they use to cling to the shore. They play an important role in ocean ecosystems.

What abalone eat:

• Kelp
• Other types of seaweed
• Algae

Adults focus mainly on eating kelp, especially the giant kelp found in deeper waters.

Juvenile abalone often eat small algae until they grow bigger.

They slowly crawl along the rocks, using their tongue-like radula to scrape up plants for food.

Abalone are considered herbivores, which means they eat mostly plants. Their diet may change based on where they live.

For example, in Southern California, they feed mostly on giant kelp and feather boat kelp.

In other areas, they also eat tangle kelp and sometimes smaller seaweed types.

Learn more about the food habits of red abalone at the Aquarium of the Pacific.

Because abalone eat seaweed and kelp, they help keep kelp forests healthy and balanced.

More details about their relationship with seaweed are shared by the Two Oceans Aquarium.

7. Crabs

Many crabs eat seaweed as a main part of their diet. Some species, like the kelp crab, actively seek out different types of seaweed, including kelp, rockweed, and sargassum.

Crabs that eat seaweed play an important role in their habitats. They help keep algae growth under control.

For example, the Caribbean king crab will eat seaweed that other animals leave behind, helping coral reefs recover from too much algae.

You can read more about the Caribbean king crab’s diet and impact at this article on seaweed-eating crabs and coral reefs.

Some types of crabs, like the northern kelp crab (Pugettia producta), focus on eating brown algae but will also eat red algae when available.

The kelp crab’s diet includes kelp, rockweed, and sargassum.

More information on what northern kelp crabs eat is shared by the University of Puget Sound.

Table: Common Seaweed-Eating Crabs

Some crabs, like decorator crabs, also eat other small creatures, but algae remain a major food source in their diets.

Crabs’ ability to feed on a variety of seaweeds makes them important for the health of the ocean environment.

8. Marine Snails (e.g., Turban Snails)

Many marine snails eat seaweed. Turban snails are some of the most common types found along rocky shorelines.

These snails use a special mouthpart called a radula. It works like a tiny file, scraping seaweed and algae off rocks.

This helps keep their habitat cleaner and gives them the energy they need.

There are several turban snail species. For example, the brown turban snail is known for its colorful shell.

Another, the black turban snail, is common in the mid to high tidal zone.

Some turban snails have been noticed for their taste. The wavy turban snail is sometimes processed as “wavalone” because its texture is similar to abalone.

Common foods for marine snails include:

• Brown and green algae
• Sea lettuce
• Kelp debris

Turban snails help support the rocky shore ecosystem. By feeding on excess seaweed, they create open space for other marine life to grow.

9. Sea Hares

Sea hares are soft-bodied marine animals that belong to the group of mollusks.

They are related to sea slugs and have large, rounded bodies with two “ear-like” structures, which is how they got their name.

These animals live in shallow waters, usually around rocks or among seaweed beds. They often rest in tide pools or among seagrass.

Diet:

Sea hares eat mostly seaweed and other types of algae. They use a tongue-like organ called a radula to scrape their food from rocks and plants.

Sometimes, they are seen eating different kinds of green, brown, and red algae.

Habitat Highlights:

• Shallow marine environments
• Rock pools
• Areas with lots of algae
  More about where sea hares live

Female sea hares can lay impressive numbers of eggs, sometimes up to eighty million at a time.

However, most of these eggs do not survive because predators eat them quickly.
Learn how sea hares reproduce

Sea hares play an important role in the ecosystem by helping control the growth of algae in their habitats.

They are a key part of rocky shore and seagrass communities.

10. Limpets

Limpets are small marine snails with distinct, cone-shaped shells.

They live on rocky coasts where waves are strong and the water is salty.

Limpets stick tightly to rocks, especially when the tide goes out.

These animals are herbivores that eat seaweed and many types of algae.

At night, limpets move slowly across rocks using their muscular foot.

They use a special tongue, called a radula, to scrape algae and seaweed from the surface of rocks.

The radula acts almost like a file, helping them gather food from tough, slippery surfaces.

Limpets often feed on various marine vegetation, including kelp and other kinds of seaweed.

You can discover more about their food habits on the A-Z Animals limpet page.

Some limpet species, like the blue-rayed limpet, are also found living on kelp itself.

Details about this unique relationship can be found on the Wildlife Trusts’ blue-rayed limpet article.

Here’s a simple list of what limpets eat:

• Algae
• Kelp
• Other seaweeds

Limpets play an important role in the ocean ecosystem by keeping rock surfaces clean and promoting healthy growth of marine plants.

This makes them key animals when discussing species that eat seaweed.

11. Brant Geese

Brant geese are medium-sized water birds found along coastal regions.

They have black heads, short necks, and white patches on their sides. These geese migrate long distances each year.

A key feature of brant geese is their diet. They are herbivores that mostly eat sea plants and algae.

Common items in their diet include eelgrass, sea lettuce, and other types of seaweed.

During migration and winter, they gather in large flocks near shorelines to feed.

Main Foods Eaten by Brant Geese:

At low tide, brant geese walk through shallow waters to pull up plants.

They rarely dive for food, instead preferring to graze in areas where vegetation is easily reached.

In some places, these geese may also eat grass or winter-sown crops if natural food is scarce.

Brant geese play an important role in their coastal environment.

By eating seaweed and plants, they help keep the shoreline habitats balanced. To learn more, visit this Brant facts page.

12. Seagulls

Seagulls are found near oceans, lakes, and rivers, making them common in many coastal areas.

They are opportunistic feeders, which means they eat a wide range of food.

Seaweed is one of the foods seagulls eat, especially when other options are limited.

They often pick through seaweed washed up on shore looking for small animals, but they will also eat the seaweed itself.

What Else Do Seagulls Eat?

• Fish
• Insects
• Worms
• Crabs
• Eggs and chicks of other birds
• Grains and seeds
• Human food scraps

Some seagull species, like the kelp gull, are known for their flexible diet.

Kelp gulls live in the Southern Hemisphere and often eat marine plants, including seaweed, along with meat and scraps.

Seagulls use their sharp beaks to tear seaweed apart.

Sometimes, small crustaceans and insects are hiding in the seaweed, giving seagulls even more food to find in one spot.

When natural food is hard to find, seagulls rely more on seaweed and marine plants for nutrition.

Seagulls are important in many ecosystems because they help clean up dead plants and animals.

By eating seaweed and other debris, they help control the amount of decaying material on beaches. This also lowers the spread of disease.

13. North Ronaldsay Sheep

The North Ronaldsay sheep live on North Ronaldsay, the northernmost island of Orkney, Scotland.

This rare breed is famous for eating seaweed instead of grass.

Most of their diet—about 80%—comes from seaweed during much of the year.

These sheep face harsh weather and rocky shores. They have adapted over centuries to survive mostly on the seashore, where grass is hard to find.

Farmers built a stone wall around the island in the 1800s, which keeps the sheep on the shore and away from farmland.

Some unique features of the North Ronaldsay sheep include:

• Hardy wool: Suits the cold, wet climate.
• Small size: Helps them move easily on rocky beaches.
• Special digestion: Their stomachs can break down seaweed, something most sheep cannot do.

Here is a quick comparison:

The North Ronaldsay sheep are one of the only land mammals with a diet based mainly on seaweed.

Their unique way of living helps them survive in a place where most sheep would struggle.

Today, the breed is important for its history and its special relationship with the island’s ecosystem.

14. Cows (Fed Seaweed In Some Coastal Areas)

In some coastal regions, farmers add seaweed to the diet of cows.

This practice has a long tradition in places where fresh seaweed washes up on beaches.

Farmers use local types such as kelp, rockweed, and bladderwrack.

Researchers have studied what happens when cows eat seaweed.

Feeding cows even a small amount—like one quarter of one percent of their feed—can reduce methane emissions by up to 30% in some tests.

One study found certain tropical seaweeds, such as Asparagopsis, can cut methane by as much as 82% in beef cattle.

Learn more about these results at Feeding Cattle Seaweed Reduces Their Greenhouse Gas Emissions.

Benefits of feeding seaweed to cows may include:

• Lower greenhouse gas emissions
• Improved feed efficiency
• Supporting sustainable farming practices

Cows benefit from a varied diet, and in coastal areas, seaweed is a natural addition. Using seaweed as part of cattle feed is one example of how farmers combine tradition with modern research to help both their herds and the environment.

Seaweed feeding is not common everywhere, but interest is growing as people look for ways to reduce the climate impact of dairy and beef farming.

Find out more about this practice at Farmers turn to seaweed in attempt to reduce methane emissions.

15. Deer (Occasionally Eat Washed-Up Seaweed)

Deer are known plant eaters, usually feeding on grasses, leaves, twigs, and fruits.

In some coastal areas, they have been spotted eating seaweed found along the shore.

When freshwater plants are scarce, especially in winter or early spring, deer may look for other food sources.

Washed-up seaweed can provide a salty treat and extra nutrients that are missing from their ordinary diet.

Some people even call seaweed “nature’s salt lick” for deer.

One interesting observation is that eating seaweed might help with antler growth.

There is some evidence suggesting that the minerals found in seaweed, like iodine and salt, may support healthier antlers.

Below is a list of reasons why deer might eat seaweed:

• Lack of normal plants during certain seasons
• Extra salt and minerals
• Easy access on some beaches
• Curiosity and opportunity

A video shows wild deer eating seaweed from the shoreline.

This behavior is not common everywhere, but it happens in some coastal regions where both deer and seaweed are present.

Not all deer eat seaweed, and it is not a major part of their diet.

Still, it is a good example of how animals sometimes try new foods when the chance comes up.

Deer will often eat what is available to survive and stay healthy.