How Many Calories Do Dolphins Eat Daily?

dolphin eating

Story at-a-glance -

  • Researchers caught (and then released) 32 common bottlenose dolphins, then measured their respiratory flow rates and expired oxygen during voluntary breaths on land or in water
  • This allowed the researchers to figure out the dolphins’ metabolic rates both at rest and while active and estimate the number of calories they’d need to survive
  • For a 440-pound (200-kilogram) dolphin, this amounted to somewhere between 16,500 and 33,000 calories a day; a dolphin would need to eat 22 to 55 pounds of fish to keep up with this demand
  • For comparison, blue whales can easily eat 457,000 calories in one bite

By Dr. Karen Shaw Becker

Dolphins spend their days swimming, diving, actively looking for food or traveling from one point to another — all activities that require considerable amounts of energy. How much energy exactly is the question researchers from Woods Hole Oceanographic Institution and the Oceanogràfic Foundation in Spain set out to answer. Finding out the number of calories required by an average dolphin on a daily basis isn’t only an interesting factoid to bring up around the water cooler, however.

It’s essential to protecting the species. Researcher Andreas Fahlman, Ph.D. explained to BBC News, “We can … add this up for all dolphins and estimate how much fish/prey they need … This may be vitally important when considering managing fisheries and making sure that the quota are not too high so that animals lack food."1

Dolphins Need Up to 33,000 Calories a Day

In order to estimate the energy requirements of an average dolphin living in Sarosota Bay near Florida, researchers caught (and then released) 32 common bottlenose dolphins, then measured their respiratory flow rates and expired oxygen during voluntary breaths on land or in water. They then used this data to measure the dolphins’ resting oxygen consumption rate and tidal volume (the amount of air inhaled during a normal breath) while at rest.

This allowed the researchers to figure out the dolphins’ metabolic rates both at rest and while active and estimate the number of calories they’d need to survive. For a 440-pound (20-kilogram) dolphin, this amounted to somewhere between 16,500 and 33,000 calories a day.2

A dolphin would need to eat 22 to 55 pounds of fish to keep up with this demand,3 which is less than researchers expected. The measurements of lung function — a first for wild dolphins — was also expected to help gauge the respiratory health of these stunning creatures. If problems exist, there could be environmental reasons to blame.

Blue Whales May Eat 500,000 Calories — in One Bite

While 33,000 calories a day may sound like a lot, it pales in comparison to the amount required by blue whales, the largest animals on the planet. Jeremy Goldbogen, Ph.D. formerly with the University of California, San Diego, and colleagues tagged 265 blue whales living off the coast of California and Mexico, which allowed him to gather data about the whales’ feeding lunges.

In addition to revealing that the whales can accelerate to 8 miles per hour in less than one minute, it was estimated that each lunge required about 770 to 1,900 calories to carry out.4

Again, this sounds like a lot, until you understand the caloric payoff that a whale receives from a feeding lunge. These filter feeders open their mouths, scooping up both water and the tiny organisms it contains, including one of their favorite foods, krill. If it happens to swim through a dense swarm of krill, the study found, blue whales can easily eat 457,000 calories in one bite, making their feeding lunges incredibly efficient.5

In short, the whales were able to take in up to 237 times more energy than they used. This may help explain how blue whales — which face environments with very little food available when migrating to their breeding grounds — are able to survive seasonal starvation, according to Goldbogen’s colleague Robert Shadwick of the University of British Columbia in Vancouver, Canada.6

But, like dolphins, whales are dependent on there being enough food supply in the sea to survive. As the researchers noted, “foraging efficiency for blue whales is significantly higher than for other marine mammals by nearly an order of magnitude, but only if lunges target extremely high densities of krill.”7

What Do Dolphins and Whales Eat?

As carnivores, dolphins (which are toothed whales) eat a variety of marine life including fish, shrimp, jellyfish, octopuses and squid. Some dolphins, such as Amazon river dolphins and Commerson’s dolphins, also eat crustaceans. Orcas, the largest dolphin, eat fish as well, although some eat larger prey such as sea lions, seabirds, other dolphins and whales.

Dolphins hunt using echolocation, which allows them to find prey even when the water is murky. And while dolphins do have teeth, they don’t chew their food; they swallow it whole.8

Baleen whales, including blue whales, consume food by opening their mouths and letting their baleen bristles, which resemble the teeth on a comb, filter food from the water. Baleen whales consume large quantities of tiny prey including krill, fish, squid, octopus, small crabs and crustaceans, and benthic animals, such as sea sponges.9

Sadly, both whales and dolphins are threatened by overfishing. A report by the Convention on the Conservation of Migratory Species of Wild Animals (UNEP/CMS) revealed, for instance, that 86 percent of toothed whales are at risk of becoming trapped as by-catch by trawls, longlines and other fishing equipment used throughout the oceans. Further, 13 species of toothed whales are facing decreasing food supplies because of humans’ overfishing.10

Dolphins in the Mediterranean may be so hard-hit by overfishing that they’re breaking into nets in order to eat the fish caught inside. “Effective management of fish stocks is urgently required to address the overexploitation that is likely driving depredation behavior in dolphins, that in turn leads to net damage and the associated costs to the fisheries,” researchers wrote in Human Ecology.11

If you want to avoid contributing to the problem, look for the Marine Stewardship Council certification on seafood, which ensures the seafood you buy can be traced back to a sustainable source.12

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