The ancestors of dolphins are land mammals and dolphins are related to land mammals living today including, most closely, the hippopotamus.
The largest dolphin, the orca, is somewhat confusingly called a killer whale. Make no mistake though, the orca, and all other dolphins may look cute, but are carnivores that eat only meat. Thankfully the relationships between humans and dolphins have been mostly good. However, some incidents of violence against humans by dolphins in captivity show this relationship may be strained when we keep dolphins locked up.
It may be that because dolphins are very social animals, captivity has a more negative effect on them than other animals.
27 Interesting facts about Dolphins
As scientists gather more dolphin facts, it should become more apparent that these are some of the most behaviorally developed animals and may deserve special rights of protection from humans who want to hunt them or keep them in captivity.
1. There Are over 30 Dolphin Species
Dolphins are aquatic mammals that live all over the world. There are over 30 species of dolphins, and they are all carnivores that eat fish, squid, and, in the case of the Orca, seals and other marine mammals.
Of the more than 30 species of dolphin, most live in the oceans of the world. However, 5 species of dolphin live in rivers. These 5 river dolphins are not all part of the same lineage. They are not directly descended from a single river dolphin. Some of these river dolphins are more closely related to oceanic dolphins than to other river dolphins.
River dolphins all descend from oceanic dolphins that retreated into river habitats when they were displaced by other oceanic dolphin species. Scientists see these river dolphins as evolving in convergent evolution, with each lineage evolving separately to live in rivers.
2. Dolphins Range from 4 ft. to 30 ft. Long
There are a wide variety of species of dolphin in the ocean within a group of animals called agenera. The smallest dolphin in the world is the Maui’s dolphin, which is only 4 ft. long.
The largest dolphin in the world is the orca, which is commonly known as the killer whale. However, it’s technically not a whale, but it is part of the genera of dolphin. Orcas can be up to 30 ft. long.
All dolphins descend from land mammals that transitioned back to life in the ocean. The amazing varieties of the more than 30 different species of dolphin evolved over time from these land mammal ancestors.
3. The Ancestors of Dolphins Entered the Water 55 Million Years Ago
Dolphins are the descendants of land mammals that returned to the ocean over 50 million years ago. This was so long ago, that other animals that descended from the same land mammals as dolphins include giraffes and hippopotamuses.
In modern dolphins, there are two bones near the pelvis that are believed to be what is left of the hind limbs of the ancestor of the dolphin. Though they appear differently in various species, these two bones appearing in all dolphins are called vestigial limbs.
Although whales and dolphins appear on the surface to be similar, they evolved separately from each other. Dolphins and whales share different features with their distant relatives such as zebras, camels, and the more closely related hippopotamus.
4. Killer Whales Are Actually 30 ft. Long Dolphins
One of the most surprising dolphin facts is about an animal that is confusingly called the killer whale. The orca, or killer whale, is scientifically considered a dolphin. Orcas live all over the world, from the Arctic to the Antarctic.
The orca is the only living species in the lineage Orcinus. When dolphin species began to emerge about 11 million years ago, the Orcinus lineage branched off at around the same time. This explains why their features and their size – they are the biggest dolphins at 30 feet long – are strikingly different from other dolphin species.
Some scientists believe that there could be 3 or 5 different species of orca. The various types of orcas lead different lifestyles and have different features.
This is one of the dolphin facts that demonstrates evolution in progress. These different orcas are developing different features to aid them in their environments: in coastal waters, in deep seas, and migrating between the two. What scientists may be observing is the emergence of new subspecies of dolphins!
5. Amazon River Dolphins Sport Goatees and Can Turn Their Head 90 Degrees
As part of their adaptation to marine life, dolphin species lost the hair that their land mammal ancestors had. When dolphins are gestating, and when they are born, they may have small hairs around their beak or mouth. However, these hairs fall off right before or after the dolphin is born.
Amazon river dolphin facts teach us that there is an exception to this rule. Amazon river dolphins have many unique features compared to other dolphin species, and one of these is that they keep the hairs on their chin, or beak, into adulthood. Perhaps the Amazon river dolphins are the beat poets of the dolphin clade and they like to sport a goatee.
Looking more closely at these dolphin facts, it may be that these hairs play a role in navigating the tight confines where the jungle meets the river in the Amazon, helping the river dolphins sense their prey. Amazon river dolphin facts also reveal that these dolphins do not have fused neck bones. This is another adaptation for life in the close quarters of the river and allows the Amazon river dolphin to turn its head 90 degrees.
6. Dolphins Can Hear 10 Times above the Human Range of Hearing
Dolphins have sharp senses which allow them to capture prey in the water. They have good eyesight so they can see their prey.
Dolphins also have an incredible range of hearing, and use a series of vocalizations, including clicks and whistles, to echolocate their prey. Interesting facts about dolphins reveal that they have an organ in their head called a melon which helps them collect sound by acting like a big radar dish.
Dolphin hearing is mostly done through vibrations in the dolphin’s lower jaw. There is a void filled with fat that connects from the lower jaw to the inner ear of the dolphin. This natural reverb chamber transmits the sound from the jaw to the inner ear.
7. Cute and Carnivorous – Dolphins Only Eat Meat
We don’t need dolphin facts to tell us that dolphins are some of the cutest marine animals. Even the orca, or killer whale, is considered cute, and plush toys of dolphins and killer whales are some of the most popular children’s stuffed animals.
Make no mistake though, dolphins are predators, and they are carnivores, meaning they eat only meat. Dolphins typically eat fish, but also eat other marine animals, including squid. Larger dolphins, such as the orca, will eat other mammals such as seals, and even whales that are larger than the orca.
The orca may be the best dolphin to compare to the T-Rex. At 30 ft. long and with large teeth, there are no known predators of the orca. The orca is one of the top predators in the ocean and is known as an apex predator. Many river dolphins, including the Chinese river dolphin, are also apex predators.
Humans and dolphins generally get along. However, there have been instances of orca-killing trainers while held in captivity. These sad dolphin facts show that the behavior of dolphins changes in captivity, and many people believe no dolphins should be held against their will.
8. Dolphins Have Big Parties – Sometimes Over 1,000 Dolphins Hangin’ Out
Dolphins are very social animals. Dolphins communicate with each other through their vocalizations, including clicks, whistles, and chirps. Some bottlenose dolphins facts have recently been revealed and show these dolphins have unique whistles that identify each dolphin. These dolphins have names! After all, when you’re being social or gossiping, it helps to know who you are talking to or who you are talking about!
Being social animals, dolphins often congregate for hunting and simply to have fun. Adolescent dolphins of certain species form groups. To put it another way, the equivalent of teenage dolphins like to hang in cliques. Dolphin facts have yet to reveal which table is the cool table at lunchtime.
Dolphins congregate in groups ranging from a few individuals to over 1,000 dolphins. Solphin groups are called pods, and these large gatherings of over a thousand dolphins are called superpods. One thing is for sure, dolphins know how to throw a big party!
9. Bottlenose Dolphins Teach Each Other to Use Tools
In addition to a complex range of vocalizations, which some scientists believe qualifies as language, dolphin facts show that certain dolphin species use tools. Putting language and tools together, some scientists attest that dolphins have culture.
The Indo-Pacific bottlenose dolphin has a special way of hunting for fish in the sand and rocks at the bottom of the ocean. To prevent its mouth or beak from being hurt by the sand and rocks, the dolphin will pick up a sponge with its mouth and use that to dig amongst the sand and rocks, thus stirring up any fish that might be hiding there. This is a learned behavior that is passed along by the mother to her offspring.
Other species of dolphins are reported to use sticks and aquatic weeds as part of mating rituals in another type of learned behavior. It’s clear from dolphin facts that these are some of the most behaviorally developed animals on Earth.
10. In Laguna, Santa Catarina, Brazil, Dolphins and Humans Fish as a Team
Humans and dolphins have had cooperative relations dating back to Roman times. In particular, fishermen and dolphins can work as a team to fish. Here’s how it works: the dolphins will work together to herd schools of fish towards the fishermen’s nets. Once the fish are caught, the fishermen give the dolphins their share of the catch. This practice continues today in places such as Laguna, Santa Catarina, Brazil.
The United States Navy also has a dolphin-training program. While there has been speculation about dolphins being trained for combat, there are no hard dolphin facts that confirm dolphins have been trained for combat in the United States or in the former Soviet Union. The US Navy and other countries have confirmed that they train dolphins for detecting mines and rescuing people who are lost at sea.
11. Dolphin pregnancies last between 9 and 16 months.
The mother feeds her baby dolphin on milk. The sons and daughters of resident orcas stay with their maternal family for life.
12. Dolphins can move fast – when they want to
Bottlenose dolphins tend to be quite slow swimmers with an average pace of two miles an hour. But if needed they can get up to 30 miles per hour but not for too long.
13. They can turn off half of their brain
When dolphins are asleep they literally keep one eye open. This is because only half of their brain is shut down. This allows dolphins to constantly be on the lookout for potential predators and also allows groups of dolphins to keep their eyes (or eye) on each other.
14. Fishing equipment is a major problem for dolphins
Unfortunately, dolphins are often killed unintentionally by fishing equipment. This includes things like gillnets, hook-and-line gear, trawls, and other tools and devices commonly used by fishermen. Work is currently being done between animal activists and fishermen to come up with new materials to avoid this issue.
15. Dolphins have two stomachs
One is for digestion and the second is for the storage of food.
16. Dolphins are great divers
They can dive up to 1,000 feet underwater.
17. Dolphins will migrate if there isn’t enough food
Generally, dolphins are not migratory animals. However, if the climate changes in a way that doesn’t suit them or if food is no longer available they will move.
18. Dolphins have sensitive skin
Dolphin skin is easily injured as it is very delicate. But luckily for dolphins, they are also quick healers from even deep wounds. Their outer skin can regenerate in just two hours.
19. Dolphins don’t drink water
They receive the moisture they need from the food they eat.
20. Dolphins are believed to have the longest memories in the animal kingdom.
21. Dolphins breathe like humans
Like us, dolphins have lungs that allow them to breathe. However, they couldn’t live on land as they would quickly overheat and become dehydrated once out of the water.
22. Like humans, dolphins also like to surf.
23. Dolphins do bite
But generally only when they are provoked through anger or fear.
24. Dolphins have been declared to be “non-human persons” in India, Hungary, Costa Rica, and Chile.
This means they cannot be captured and used for entertainment purposes.
25. Some countries are known to kill dolphins for human consumption.
Those countries are Japan, Peru, Solomon Islands and the Faroe Islands
26. Dolphins have been in a lot of movies.
The best-known dolphin movies are Flipper, The Day of the Dolphin, Dolphin Tale, The Cove, and Zeus and Roxanne.
27. Dolphins may date back to ancient cultures
The lost city of Petra in Jordan features carvings of dolphins in some of its rocks. It is believed that Petra may have been established as early as 312 BC.