There’s no doubt that dolphins have carved themselves a special place in the human heart. From the movie Flipper to playful wild dolphins, their “smiles” and exuberant demeanor are incredibly endearing. But it’s not all fun and games in the animal kingdom. Dolphins are skilled predators that all too often fall prey to humans. To find out how many dolphins are left in the world, the difference between a dolphin and a porpoise, and whether dolphins are endangered, read on.
How Many Dolphins Are Left in the World?
There are millions of dolphins left in the world, at least 8 million and possibly several millions more. One of the most common dolphins, the bottlenose, has around 600,000 members worldwide. The pantropical spotted dolphin has as many as 4 million. Because dolphins are wide-ranging and sometimes change their pod sizes, it is very difficult for scientists to calculate their numbers precisely.
Dolphins are split into 42 different species. Scientists are considering a 43rd, the Burrunan dolphin. Thirty-eight of these species belong to the oceanic dolphin family Delphinidae. The other four confirmed species are river dolphins, each the sole member of their family.
Species of Dolphins
Scientists divide dolphins into oceanic and river dolphins. River dolphins have much larger and longer snouts suitable for digging for food in riverbeds. Their eyesight is also much weaker, probably due to the reduced visibility.
Oceanic dolphins are much more playful than their river cousins, occasionally leaping bodily out of the water. This is the result of having more space in which to move. Oceanic dolphins are also much faster swimmers.
Oceanic Dolphin Species
There are 38 species of oceanic dolphins. The most familiar is the bottlenose dolphin, commonly portrayed in movies and TV shows. This genus contains 2 distinct species: the common bottlenose dolphin (Tursiops truncates) and the Indo-Pacific bottlenose dolphin (Tursiops adunctus).
Other species include:
- Long-beaked common dolphin, Delphinus capensis
- Northern right whale dolphin, Lissodelphis borealis
- Pantropical spotted dolphin, Stenella attenuata
- Spinner dolphin, Stenella longirostris
- Long-finned pilot whale, Globicephala melas
Despite their name, killer whales (orcas) are actually members of the dolphin family. They are the largest and most aggressive members, apex predators of the ocean.
River Dolphin Species
There are 4 species of river dolphins, each in its own family. They are:
- Amazon river dolphin (also known as the boto), Inia geoffrensis
- South Asian river dolphin (also known as the susu, shushuk, or the Indus River Dolphin), Platanista gangetica
- Chinese river dolphin (Baiji), Lipotes vexillifer
- La Plata dolphin (Franciscana), Pontoporia blainvillei
Sadly, the Chinese river dolphin is functionally extinct.
Dolphin vs Porpoise
What is the difference between a dolphin and a porpoise? Many people confuse these two mammals, but there are significant differences between them. Both belong to the order Cetacean, which includes whales. However, most dolphins belong to the family Delphinidae, while porpoises belong to Phocoenidae.
They are relatively easy to tell apart by their noses. Dolphins have long, protruding snouts, while porpoise snouts are blunt and beakless. Dolphins have bigger mouths. In addition to this, dolphins have sleeker bodies and larger dorsal fins. Porpoises appear thick and stout.
Porpoises prefer colder waters like those of the Northern Pacific and Atlantic oceans. They stick to shallower waters, unlike dolphins, which venture out further. Dolphins usually seek out warmer, tropical waters.
Color also differentiates these two mammals. Porpoises exist in shades of black, gray, and white. On the other hand, dolphins can be black, gray, white, pink, blue, or brown.
Where Are Dolphins Found?
Dolphins live in oceans and rivers around the world. Oceanic dolphins prefer warm coastal waters or shallows. They inhabit every ocean in the world. River dolphins inhabit rivers in Asia and South America containing either brackish or freshwater.
Dolphins are warm-blooded, which means they can regulate their body temperature. This helps them survive in several different habitats, including the colder waters of the Northern Pacific Ocean.
Dolphin Diet and Predators
Dolphins are carnivores, meaning they only eat meat. Their usual diet consists of fish, crustaceans, squid, and jellyfish. Larger dolphins, like killer whales, will also attack seals, sea lions, and sharks. Occasionally, dolphins will eat other dolphins or porpoises. If they get the chance, they may snatch birds out of the air or off the water’s surface.
Dolphins hunt by echolocation. They make clicking sounds that help them locate fish or other animals in the water. They surround their prey as a pod and attack it.
Being apex predators, dolphins fear little in the water. However, sharks sometimes attack, especially if they can isolate a young or weak pod member. Common shark attackers include great whites, dusky sharks, bull sharks, and tiger sharks. Killer whales are not above eating other dolphins. Humans also hunt them, accounting for a significant percentage of yearly deaths.
The World’s Biggest Dolphin
The world’s biggest dolphin is the killer whale or orca. Its scientific name is Orcinus orca. The average killer whale measures between 23 and 32 feet in length. On average, killer whales weigh between 8,000 and 16,000 pounds.
Because of its size and name, people often mistake this mammal for a whale. It makes an extremely aggressive apex predator in its natural environment. In captivity, however, it is a popular tourist attraction. It shares the intelligence of its fellow dolphins and can learn tricks and outsmart its prey.
The largest killer whale ever recorded stretched 32 feet in length. It weighed an astonishing 22,000 pounds!
Are Dolphins Dangerous?
Dolphins are predators, which means there is always an element of danger in our interactions with them. Dolphins have occasionally bitten or butted humans while swimming or playing with them. However, they rarely attack people, and when they do, fatalities are rare. Like most animals, dolphins can be more aggressive during mating or when protecting their young.
Dolphins often chase boats or swim alongside them, sometimes butting up against them. This is a result of natural curiosity and playfulness, not aggression. Curiosity is a sign of intelligence, and dolphins are among the smartest species in the world. They communicate in complex ways, use tools, and engage in problem-solving!
Are Dolphins Endangered?
Conservationists list all species of river dolphins as either endangered or critically endangered. One species, the Chinese river dolphin, is functionally extinct.
Most oceanic dolphins are not endangered. However, there are a couple of exceptions. The IUCN lists both the Atlantic humpback dolphin and the Maui dolphin, the smallest dolphin in the world, as endangered.
Human fishing and pollution are the top causes of dolphin depletion. Fishermen often catch dolphins in gillnets while hunting them for their meat or to eliminate them as predators. Sometimes, dolphins are collateral damage as fishermen seek other targets.
Dolphins are valuable members of their ecosystems, and it is vital to preserve them for the health of their environments.
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