Dolphins, renowned for their intelligence and playful demeanor, have captivated humans for ages. These marine mammals exhibit complex social behaviors and varied diets that reflect their diverse habitats and species. This article explores the fascinating world of dolphin diets, examining what they eat, how they hunt, and the impact of their feeding habits on the marine ecosystem.
Dolphins as Marine Mammals
If you’re reading this, we have a lot in common. Dolphins may swim through the water as gracefully as any fish, but they are not fish. Dolphins are mammals, placing them in the ranks of other famous marine mammals such as whales, seals, and manatees. So why are dolphins mammals? They are warm-blooded, meaning that their body is able to regulate its own temperature, so they stay warm even when the water temperatures around them are cold. Some of their native environments, such as the waters of the northern Pacific Ocean, can get very chilly. In these places, being warm-blooded is a big advantage for survival. Another central feature of marine mammals is that they have lungs, not gills. Dolphins, like whales, need to periodically come to the surface to replenish their air supply. Marine mammals have also adapted in some special ways to thrive in an aquatic environment. For instance, dolphins exchange 80% of the air in their lungs with each breath, while humans are only capable of exchanging 17%. Marine mammals also have a greater capacity for oxygen storage in their lungs, blood, and muscles. Dolphins give birth to live young and do not lay eggs. They can get pregnant on average every two to four years once they're mature, although some species can have 5-7 years between births. Dolphin calves tend to stay close to their mothers for a few years before venturing off on their own. Along with gestating their young, dolphins produce milk to nourish them. Did you know that dolphins start life with body hair? Dolphins are considered one of the world's most intelligent animals, and they have several cognitive abilities that set them apart. Many researchers consider intelligence to be a combination of perception, communication, and problem-solving. Communication is a big part of how dolphins socialize and hunt. They have the ability to echolocate with a series of clicks, allowing them to find other dolphins or similar species and prey even in the low-light conditions of the ocean. They can do more, too. Did you know that dolphin echolocation allows them to detect surgically implanted metal in swimming humans? The human body is comprised of about 75% water, and once in the water, we provide a prime structure for echolocation. This is how dolphins are able to discern that the metal is denser than human flesh, which is mostly water. Dolphins also have a complicated method of communicating with each other. From an outside perspective, dolphins may seem to communicate much like humans. Despite lacking hands, dolphins are adept at using tools. For instance, one of their more specialized tricks is to carry a sponge at the end of their beak, also know as a rostrum. Zoological facilities, aquariums, and other places, such as Dolphins Plus, give people a way to learn more about these remarkable animals. The educated professionals who work there can share general information, threats and conservation efforts, and the latest research findings on how these animals cognitively function, communicate, and adapt. One of the fascinating things about these marine mammals is their complex methods of communication. So how do dolphins communicate? Dolphins communicate through more than just clicks and whistles. Dolphins can make squeaks, buzzes, whistles, clicks, and a wide array of other crazy noises. These whistles can be heard by others of the species from miles away. Echolocation serves for both communication and for navigation. Echolocation is seeing with sound, much like sonar on a submarine. The dolphin emits a sound and then listens for the echo as that sound bounces off of objects, these sound waves travel back to the dolphin. Dolphins are able to get much more information out of the sound than humans. There are dozens of species of dolphins and each has their own unique habitats, appearance, and behaviors. In terms of behavior, all species of dolphins are quite gregarious. In fact, many dolphin species can form groups of over 1,000 individuals, known as super pods! Dolphins come in all shapes and sizes, and each species has their own unique features. You may not expect to find a dolphin in freshwater areas, but this species thrives in the Amazon River. Here's another entry to the list of freshwater dolphins. As you'd guess from the name, this species can be found in the Ganges River in India. This striking, highly social dolphin species is found off the coast of Argentina and in parts of the Indian Ocean. Risso's dolphins love deeper waters, where they seek out a diet of squid and other deepwater fish species. Did you know that killer whales are members of the dolphin family? These animals, also commonly called orcas, are the world's largest dolphins. How big are they? Larger individuals can grow over 30 feet long and weigh 11 tons. They typically have a bold black and white pattern similar to Commerson's dolphin. These playful dolphins have earned their name, in part, for the high jumping spins they take out of the water. These aerial acrobatic tricks make them a favorite among dolphin-watchers. Once you've seen one of these members of the dolphin family, you'll never forget them. The short-finned pilot whale has an unusual, squared-off head and lacks the long beak of most dolphin species. This shy, elusive dolphin species share a similar black and white color pattern to killer whales, but they are a fraction of the size. Although the bottlenose is the most famous dolphin species, there is a good chance you've seen a striped dolphin in action at an aquatic center. We saved the bottlenose dolphin for last for two reasons. It’s one of the most popular species. Flipper, the world's most famous dolphin, was a bottlenose dolphin. These majestic animals are dark grey and, as you'd expect from the name, have a short and blunt rostrum. Bottlenose dolphins are varying shades of grey with a lighter belly (counter-shading), which helps conceal them from predators. They have a streamlined body that allows them to swim up to 20 mph. The bottlenose dolphin's diet varies depending on the region where they live. These skillful predators primarily eat fish, but can also hunt other marine life such as squid. Dolphins have some sophisticated ways to catch a meal. Some of their tactics include herding prey into muddy areas and even catching leaping fish out of the air. Dolphins thrive in both tropical and cooler, more temperate waters. Humans have encountered dolphin pods both near shore and in deep offshore waters like the Indian Ocean. When their calves are born they typically weigh around 30-40 pounds, compared to full-grown dolphins that can weigh over a 1,000 pounds. That's quite a difference!
What Do Dolphins Eat? A Look at Their Diverse Diets
Dolphins are carnivores and eat other animals. In the wild their diet consists of a variety of fish, squid, jellyfish, shrimp and octopus. There are actually more than 40 species of dolphin that live in environments ranging from fresh water rivers, estuaries, coastal waters to deep sea open oceans. Mostly, dolphins eat fish. Surprising? No. Fish form a significant part of a dolphin’s diet. The specific diet of a dolphin can vary greatly depending on its species and habitat. Oceanic dolphins, like the common bottlenose, mainly feed on fish and squid.
Fish as a Staple Food
Regardless of the habitat of dolphins, fish are among the staples of the dolphin diet, including the common dolphin’s diet. While fish is a common denominator among various dolphin species’ diet, the types of fish that dolphins eat often depend on their habitat. For dolphins that live in cooler waters, salmon is a common dolphin diet staple in the warmer months. When the waters cool down, mackerel and herring become a large part of their diet. Coastal dolphins indulge in common coastal fish such as saltwater catfish, mullet, and mackerel. Bottlenose dolphins in Key West, are known to consume a wide variety of fish species, including pinfish, pigfish, ballyhoo, mullet, spot, and toadfish. From experience, they seem to eat the most of ballyhoo and mullet. For instance, bottlenose dolphins that live in Scotland love salmon, which is available in the spring and summer months.
Other Prey: Squid, Octopus, and Crustaceans
While the term cephalopod may be unfamiliar, you have definitely heard of these creatures. The cephalopod class includes well-known oceanic creatures such as squid and octopus. Squid and octopus are another dolphin diet centerpiece. Squid, in particular, are included in the common dolphin’s diet. Humans and dolphins alike have crustaceans in their diets. Specifically, dolphins are well-known to eat shrimp and crab. Shrimp, crab, and other crustaceans are common elements of dolphin diets from various habitats. Risso's dolphins love deeper waters, where they seek out a diet of squid and other deepwater fish species.
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Jellyfish Consumption
Jellyfish are another dolphin diet staple. So far, most of the foods that dolphins consume have been fairly similar to that of humans, but jellyfish are where their diets diverge. Dolphins generally do not eat jellyfish. While they are capable of catching and consuming a wide variety of marine creatures, jellyfish are not a preferred food source due to their low nutritional value and the potential for stings from species with venomous tentacles.
The Special Case of Orcas
While bottlenose dolphins do not eat seals, some members of the dolphin family, such as orcas (killer whales), do. Orcas are apex predators with a diverse diet that includes fish, squid, seabirds, and marine mammals like seals. Orcas, or killer whales, are the top predators in the ocean. They have a varied diet that depends on the pod’s location and hunting strategies, and they are known to eat almost anything. For example, resident orcas primarily feed on fish, particularly salmon. Their range includes central California to southeast Alaska, but their core range is in the coastal waters of Washington and southern Vancouver Island, and the Salish Sea. In contrast, transient orcas, which are often found in open ocean areas (coastal and offshore waters of the Pacific Northwest, from southern Alaska to central California) specialize in hunting larger prey, such as seals, sea lions, and even young whales. Off the coast of South Africa, orcas have learned to hunt and kill great white sharks in under two minutes-faster than their typical group hunts. In recent news, a pod of orcas off the coast of Mexico has developed a clever strategy to hunt and kill whale sharks, the world’s largest fish, which can grow up to 60 feet long. While previous reports suggested orcas targeted whale sharks, new research has documented this behavior in detail for the first time, capturing four separate hunting events on camera.
Freshwater Dolphins
You may not expect to find a dolphin in freshwater areas, but this species thrives in the Amazon River. Here's another entry to the list of freshwater dolphins. As you'd guess from the name, this species can be found in the Ganges River in India. River dolphins, such as the Amazon river dolphin (also known as boto) and the Indus river dolphin of India, are adapted to living in freshwater rivers rather than the open ocean. Their diet primarily consists of freshwater fish, which can vary greatly depending on their habitat. One of the most notable traits of river dolphins is their ability to navigate through narrow, often murky waters. Amazon river dolphins are known to eat more than 40 different species of fresh water fish.
Hunting Techniques: How Dolphins Catch Their Prey
Dolphins are active predators and eat a wide variety of fishes, squids, and crustaceans such as shrimps. Some offshore dolphins were found with deep-sea fishes in their stomachs. Dolphins have some sophisticated ways to catch a meal. Some of their tactics include herding prey into muddy areas and even catching leaping fish out of the air. Dolphins are skilled hunters with diverse diets that reflect their adaptability and intelligence. From fish and squid to the occasional large prey like seals (in the case of orcas), dolphins play a crucial role in the marine food web. Dolphins employ sophisticated hunting techniques to locate and capture their prey. Dolphins are not just eaters, they are skilled hunters. Echolocation allows dolphins to detect prey by emitting sound waves and listening for echoes. Social hunting strategies can involve coordinated efforts and communication among dolphin pods. Dolphins’ intelligence is partly attributed to their complex hunting strategies.
Cooperative Hunting
Humans have encountered dolphin pods both near shore and in deep offshore waters like the Indian Ocean. Adult bottlenose dolphins eat approximately 4% to 6% of their body weight in food per day. In open waters, a dolphin group sometimes encircles a large school of fish and herds the fish into a small, dense mass. Famously, we will also see cooperative hunting behavior in the Keys, and the female dolphins will use a technique called “silt netting”. Silt netting takes advantage of the shallow water Seagrass flats that define the Florida Keys. The dolphins will encircle a school of fish and use their tail to stir up the silty bottom, from a birds eye view you will see mud ring form around the fish the dolphis will then either take turns swiming through the corraled fish or the fish will jump out of the water into the waiting dolphins mouths. We don’t see this very often, but it’s super cool when we do. We will also see the dolphins working together to herd fish into tight balls, making them easier to catch.
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Unique Hunting Strategies
Near the surface of the ocean, dolphins at Sarasota Bay, Florida, may roll to their sides with one pectoral flipper raised high. The dolphins encircle a school of fish, splashing their tail flukes and forcing them to bunch in a tighter and tighter group until the dolphins turn to grab a quick meal on the go. "Drivers and blockers" is a rare example of an animal hunting technique that demonstrates a clear division of labor. While hunting fish, some of these highly specialized groups are "divers" who smack the water's surface with their tail flukes to herd fish into a circle. Others stay less than a body length apart from each other to block and prevent fish from escaping. Occasionally dolphins herd schools of fish against sand bars, shorelines, or mud banks to trap them in shallow water where the fish are easy prey. During the hunting technique known as "crater feeding," bottlenose dolphins dive snout-first into the sandy bottom trying to grab an unsuspecting fish. Researchers have observed a small number of females carrying the sponges on their beaks, diving down, and then dropping the sponge just prior to surfacing and swallowing prey. Researchers theorize that the sponge acts as a shield to protect the dolphin's beak (rostrum) from spines of certain fishes or stingrays, or from sharp shells or rocks when the dolphin digs into sandy-bottomed habitats in search of prey. Once mullets enter shallow water off the west coast of Florida, dolphins swim around them while hitting the ocean floor with their tail flukes. This creates a ring of mud which surrounds the fish. Bottlenose dolphins often feed in association with fishing operations.
Strand Feeding
Strand-feeding is a unique hunting technique used by bottlenose dolphins, where they swim onto shallow shores to herd and capture fish like mullet. This behavior involves the dolphins using the shoreline to trap their prey, and is a highly effective method, though it requires precise timing and coordination among the group. It’s a learned behavior, passed down through generations, and is most commonly observed in regions with shallow, fish-rich waters.
Battling Aggressive Prey
In Western Australia, bottlenose dolphins will battle a more aggressive prey - the Maori octopus- which could kill the dolphins if not incapacitated properly before eating. The dolphins use two main tactics to catch octopuses. One method involves holding the octopus in their mouths, swimming out of the water, and then slamming back down to break apart the octopus’ body. The other tactic is to shake their head side to side and toss the octopus, creating a similar slamming effect. It might take some extra effort, but the reward is a high-protein meal.
Sperm Whale Hunting Techniques
Sperm whales are the largest toothed whales, and their diet is largely centered around squid, particularly the elusive giant squid that lives in the deep ocean. They are found in all deep oceans, from the equator to the edge of the pack ice in the Arctic and Antarctic. According to NOAA, “sperm whales hunt for food during deep dives that routinely reach depths of 2,000 feet and can last for 45 minutes. Their hunting technique involves diving deep into the ocean, where they rely on echolocation to locate squid in the dark depths. Once they locate their prey, sperm whales use their powerful jaws to capture and swallow their meals whole.
Baleen Whale Feeding Strategies
Baleen whales are filter feeders, meaning they use their baleen plates-comb-like structures in their mouths-to filter food from the water. Baleen whales are known to consume massive quantities of food to fuel their enormous bodies. For example, in the North Pacific a blue whale can eat up to 10 to 20 tons of krill per day during feeding season! Bubble net feeding is a remarkable and cooperative hunting technique used by humpback whales to catch large quantities of fish, particularly in deep, dense schools. This strategy involves a team of humpback whales working together to corral and trap prey using bubbles and coordination. Gray whales are the only baleen whales that primarily feed on the ocean floor. They scoop up sediment by scraping the side of their head along the seabed, capturing small invertebrates on their baleen plates.
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Dolphin Diet Facts
Here’s a fun fact, while all dolphins have teeth, they do not chew their food! Dolphins do not chew their food. Before eating large fishes, bottlenose dolphins shake them or rub them on the ocean floor until suitable-size pieces break off. Instead, they swallow their food whole. They merely grab food with their teeth, bite off a chunk, and then swallow the entire piece! Also, when dolphins metabolize, or burn their fat, water gets released in the process. Baleen whales extract their prey from seawater as it flows through or is forced through their baleen plates using their tongues and sometimes their throat muscles. While toothed whales, such as dolphins, are thought to have a keen sense of taste, they lack an olfactory nerve and associated lobes and therefore it is believed that they are not able to smell their food. They get all the water they need directly from the food they eat. Their main prey (fish and squid) contains large amounts of water.
Calf Diet
Baby dolphins, known as calves, primarily feed on their mother’s milk for the first 18-20 months of their lives. Dolphin milk is rich in fat, protein, and water, providing the essential nutrients needed for rapid growth and development. As they grow, calves gradually begin to eat solid food, such as small fish, while still nursing.
Dolphin Diet in Captivity
The dolphin diet in captivity is a little different than in the wild. For starters, instead of live, fresh fish, dolphins are served frozen fish. For instance, SeaWorld feeds their adult bottlenose dolphins a variety of fish including mackerel, smelt, capelin, and herring. Each dolphin receives 25 to 35 pounds of fish each and every day.
The Impact of Dolphin Diets on Marine Ecosystems
Dolphins play a crucial role in marine ecosystems. Their diet and feeding habits can serve as a model for understanding the behavior of other marine predators. Changes in their diet can have cascading effects on the ecosystem. Dolphins’ preference for certain types of fish can lead to competition with commercial fisheries.
Threats to Dolphins
Dolphins are under threat worldwide, mainly human generated threats. Two of the biggest issues are entanglement in fishing gear and nets, and pollution. Dolphins often pursue the same fish species that commercial fishing ships are hunting and may get accidentally caught in their nets. They can also get tangled in discarded ropes and gear, causing a significant amount of marine mammal deaths each year. Despite living throughout the world, dolphins are currently facing a lot of threats. Climate change, pollution including trash and debris, and aggressive fishing operations are impacting all species of dolphins. This is why marine mammal facilities are important for protecting and researching these animals. Human activities can have a significant impact on the diet of dolphins. Climate change is another factor that can alter the distribution of dolphin prey, thereby affecting their feeding patterns. Moreover, bycatch, the accidental capture of non-target species in fishing, can lead to a decrease in dolphin food sources. Conservation efforts play a crucial role in ensuring a healthy and abundant food supply for dolphins.
Are Dolphins Endangered?
Are dolphins endangered? Yes, there are dozens of species of dolphin that are endangered and now extinct. Some of the most threatened species are the ones that come into contact with humans most frequently. This includes the Yangtze River dolphin, the Maui dolphin, the Ganges River dolphin, and the short-beaked common dolphin. The Yangtze River dolphin is not officially considered extinct, but there have been no confirmed sightings for nearly 20 years. What may have happened? The Maui dolphin, found off the coast of New Zealand, is a highly endangered species with (an estimated) less than 100 members left. The species decline is due to many issues, one of which is that they are very slow breeders. Most dolphins reproduce an average of every couple of years, but for this species, it's 6-7 years. The Ganges River dolphin is seen in India, Nepal, and Bangladesh. Because it lives in some of the most populated areas of the world, this species is hit hard by human impact. The short-beaked common dolphin is found in the Mediterranean in declining numbers.
Conservation Efforts
The dietary needs of dolphins are an important consideration in rescue and rehabilitation efforts.
How Can You Help?
How can you help? Even small changes you make can have a big impact on the future of dolphins in the world. Most of the time, dolphins are not dangerous. Some are friendly and curious while others are skittish and avoid human contact. Are you interested in swimming with dolphins? Don't do this in the wild; appreciate them from a distance. Do not feed wild dolphins. If you see someone feeding dolphins in the wild, report them to the authorities. Do not touch or pet dolphins, even if they come close. Stay quiet and avoid loud noises. Discard unwanted or waste fishing lines safely. This last point is very important. Fishing lines, fish hooks, and discarded netting are one of the bigger threats to dolphins.