Understanding Filter Feeding

Quck answer

Filter feeding is a method of obtaining food by filtering out small particles from water or air. This method is used by many aquatic animals, such as whales, baleen sharks, and clams, as well as some birds, like flamingos. Filter feeders have specialized structures, such as gill rakers or cilia, that help them capture food particles. They can consume large amounts of water or air to obtain enough food, and this method is an important part of many ecosystems. However, filter feeding can also lead to the accumulation of pollutants and toxins, which can harm both the filter feeders and other animals that consume them.

Animal Facts

Flamingos are among the few land animals that practice filter feeding. For more bird pictures, click here.
Tui De Roy/Minden Pictures/Getty Images

Have you ever been too lazy to get up from the couch to grab a snack? Maybe you wished you could just open your mouth and let the food come to you – small bits of crackers, cookies, popcorn, or cereal – without putting in any effort to chew. If this sounds appealing to you, then you might understand filter feeders. Filter feeding is a method of aquatic feeding where an animal takes in numerous small prey items at once. Unlike predators who search for specific food, filter feeders simply open their mouths and take in whatever is available, filtering out what they don’t need. While most filter feeders are underwater creatures, ducks and flamingos also practice this feeding method [source: Hecht].

However, as a human, it is unlikely that you would rely on filter feeding all the time. Eventually, you would want to grill a juicy steak or order a cheesy pizza. But some species, including some of the largest sea fish, spend their entire lives filter feeding. For other animals, relying on ocean currents to bring their dinner is not a matter of laziness. These creatures have to travel long distances to find food, and they have adapted to filter feed to survive.

But how do they do it? Why do they do it? Is it the ultimate diet, or just an excuse to eat all day? We’ll explore what is going on with these creatures in the following sections.

Filter Feeders

This sponge could be feeding RIGHT NOW!
Hal Beral/Visuals Unlimited/Getty Images

Filter feeders come in various sizes, from small sponges to baleen whales. Around 20 fish species, including sardines and mackerel, filter feed [source: Parker]. Scientists have even discovered a dinosaur called Gallimimus that may have been a filter feeder because its fossilized beak had a sieve that filtered food [source: Hecht]. Filter feeding is one of the oldest forms of eating, with some sharks having started filter feeding between 30 and 60 million years ago [source: Parker, Martin].

All filter feeders have specialized equipment for feeding. For example, baleen whales have baleen plates instead of teeth. These plates are made of keratin, the same material that makes up hair and nails. They grow like nails and replace themselves as they wear down due to the whale’s use of its tongue. Coarse, fibrous strands on the plates form a net that captures food like schooling fish, with some whales capable of capturing creatures smaller than 5mm (0.2 inches) [source: Croll and Tershy].

Baleen whales also feed on krill, tiny shrimp-like creatures. Krill constitutes 94% of the diet of the filter-feeding crabeater seal [source: Croll and Tershy]. Crabeater seals have modified teeth that facilitate filter feeding. When they take in water with their mouths, the water is filtered out while the krill is trapped by particular postcanine teeth that have developed on both their upper and lower jaws.

It’s surprising that some of the largest sea creatures, such as baleen whales and certain sharks, are filter feeders. However, their size may actually aid them in this feeding method. When small fish are scarce, larger fish can endure periods of hunger by traveling further and longer to find food. Once they do find it, they can consume a large amount at once.

Not all filter feeders have to move around to find their food. Sponges, for example, have a system of canals and chambers that allow them to draw water in, filter out food, and consume it. Water enters through an opening called the ostra and travels through the sponge’s internal system, where collar cells capture the food. The sponge then expels the water through an opening called the oscula.

Other creatures that use filter feeding include mussels, clams, and worms. Mussels filter food particles through their gills by drawing water in through their shells, while clams use mucus on their gills to catch plankton as they push water in and out of their siphons. The worm Chaetopterus has a mucus bag that strains food particles out of the water; when the bag is full, the worm consumes it and starts a new bag.

To learn more about how sea creatures feed, check out the links below.

Originally published on May 19, 2008.

FAQ on Filter Feeding

Filter feeding refers to a method of aquatic feeding where an animal takes in multiple small prey at once while filtering out the undesirable parts. Some types of whales such as baleen whales and whale sharks are filter feeders.

Filter feeding fish eat by opening their mouth and taking in whatever is available while excluding the unwanted parts.

Sponges are not animate creatures but have a water current system made of canals and chambers that allows them to filter food and eat quite a lot.

The water enters the sponge through a pore called the ostra and travels through the system where collar cells capture the food. The sponge then expels the water through an opening known as the oscula.

Filter feeding is a simple mechanism of feeding as compared to the specialized food items predators seek.

More Information

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• Why is the world’s biggest landfill in the Pacific Ocean?

More Great Links

• Discovery Channel Shark Guide
• OceansLive
• SeaWorld
• Whale Center of New England

Sources

• “A Few Good Filter Feeders.” Chesapeake Quarterly Online. 2007. (May 8, 2008)http://www.mdsg.umd.edu/CQ/V06N2/side2/index.html
• “Animal.” EncyclopГ¦dia Britannica. 2008. (May 5, 2008)http://www.britannica.com/EBchecked/topic/25501/animal
• Croll, Donald A. and Bernie R. Tershy. “Filter Feeding.” Encyclopedia of Marine Mammals. 2001. (May 5, 2008)http://montereybay.noaa.gov/research/techreports/ucsc/crolltershytr.pdf
• “Feeding Behavior.” EncyclopГ¦dia Britannica. 2008. (May 5, 2008)http://www.britannica.com/EBchecked/topic/203727/feeding-behavior
• “Filter feeding.” EncyclopГ¦dia Britannica. 2008. (May 5, 2008)http://www.britannica.com/EBchecked/topic/207047/filter-feeding
• Hecht, Jeff. “Filter-feeding dinosaur sieved its food.” New Scientist. Aug. 29, 2001. (May 9, 2008)http://www.newscientist.com/channel/life/dinosaurs/dn1216
• Martin, R. Aidan. “Building a Better Mouth Trap.” ReefQuest Centre for Shark Research. (May 5, 2008)http://www.elasmo-research.org/education/topics/d_filter_feeding.htm
• Parker. Steve and Jane. “The Encyclopedia of Sharks.” Firefly Books. 2002.”sponge.” EncyclopГ¦dia Britannica. 2008. (May 9, 2008)http://www.britannica.com/EBchecked/topic/560783/sponge

FAQ

1. What is filter feeding?

Filter feeding is a method of feeding in which an organism, such as a whale or a clam, feeds by filtering small organisms or particles out of water or air. This is accomplished by the use of specialized structures, such as cilia or gills, which trap the particles as the water or air passes through.

2. How do filter feeders differ from other types of feeders?

Filter feeders differ from other types of feeders in that they do not actively pursue and capture their prey. Instead, they rely on the flow of water or air to bring food particles to them.

3. What are some examples of filter feeders?

Some examples of filter feeders include whales, clams, oysters, mussels, and flamingos.

4. What is the advantage of filter feeding?

The advantage of filter feeding is that it allows organisms to feed on a large volume of food particles without expending much energy. This is particularly useful in environments where food is scarce or where competition for food is high.

5. How do whales filter feed?

Whales filter feed by opening their mouths wide and swimming through large schools of small fish or krill. As the water passes through their baleen plates, the food particles become trapped, while the water is expelled through the sides of the mouth.

6. How do clams filter feed?

Clams filter feed by pumping water in and out of their bodies through their siphons. As the water passes over their gills, food particles become trapped, while the water is expelled back out through the siphons.

7. What is the difference between suspension feeding and filter feeding?

Suspension feeding is a broader term that encompasses filter feeding. Suspension feeders use a variety of methods to capture food particles, including filter feeding, as well as capturing food particles with mucus or by using specialized appendages.

8. Are there any risks associated with filter feeding?

There are some risks associated with filter feeding, particularly in environments that are polluted or where harmful algal blooms are present. In these cases, filter feeders can accumulate toxins or other harmful substances in their tissues, which can be harmful to humans or other animals that consume them.

9. How has filter feeding evolved?

Filter feeding has evolved multiple times throughout the history of life on Earth, and has led to the development of a wide variety of specialized structures and adaptations. For example, some filter feeders have developed specialized gills or cilia to filter out food particles, while others have developed complex mucus structures to capture food particles.