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Dolphins are highly intelligent marine mammals that live in water but breathe through a blowhole on the top of their head. They are remarkable creatures that have developed a form of sonar called echolocation to hunt and prey. They are very friendly and playful. 

Dolphin Facts

  • Dolphins are aquatic mammals.
  • They are a part of the species Cetacea.
  • There are almost forty species of dolphin, and they are found worldwide.
  • Dolphins measure from 5 ft 7 in (1.7 m) long and 110 lb (50 kg) in weight to over 31 ft (9 m) long and 10-tonne (9,000 kg) in weight.
  • They have streamlined bodies and two limbs that are modified into flippers. 
  • Some dolphins can briefly travel at speeds of 29 kilometers (18 mi) per hour
  • They can leap about 30 feet (9.1 m).
  • Dolphins use their cone-shaped teeth to capture their prey.
  • They have very good hearing which is adapted for both air and water. 
  • They also have a layer of fat, or blubber, under the skin to keep warm in the cold water.
  • Male dolphins are typically larger than females.
  • Most species of dolphins prefer the warm waters of the tropic zones, but some do prefer colder climates. 
  • Dolphins feed largely on fish and squid.
  • Orca, however, feeds on mammals, particularly seals. 
  • Male dolphins mate with several females each year, but females only mate every two to three years. 
  • Calves are typically born in the spring and summer months and females bear all the responsibility for raising them. 
  • Mothers of some species fast and nurse their young for a relatively long period of time. 
  • Dolphins produce a variety of vocalizations, usually in the form of clicks and whistles.
  • Dolphins are sometimes hunted in places such as Japan.
  • Dolphins are sometimes kept in captivity and trained to perform tricks. 
  • The most common dolphin species in captivity is the bottlenose dolphin, while there are around 60 orcas in captivity.
  • A group of dolphins is called a “school” or a “pod”. 
  • Male dolphins are called “bulls”, and females are called “cows”.
  • Young dolphins are called “calves”.

Anatomy

  • Dolphins have torpedo-shaped bodies with non-flexible necks.
  • Their limbs are modified into flippers and a tail fin.
  • They have a fat, round, bulbous heads. 
  • Dolphin skulls have very small eye orbits, long snouts, and eyes placed on the sides of its head.
  • They lack external ear flaps. 
  • Dolphins have conical teeth.
  • These conical teeth are used to catch swift prey such as fish, squid or large mammals, such as seals.
  • Breathing involves expelling stale air from the blowhole (situated on the top of their head). The upward blast, which may be visible in cold air, is followed by inhaling fresh air into the lungs. 
  • Dolphins have rather small, unidentifiable spouts.
  • All dolphins have a thick layer of blubber, (fat) thickness varying on climate. 
  • The primary use of their blubber is insulation from the harsh climate.
  • Blubber helps with buoyancy.
  • It also offers some protection to some extent as predators have a difficult time getting through the thick layer of fat,
  • Calves are born with a thin layer of blubber, which develops at different paces depending on the habitat.
  • Dolphins have a two-chambered stomach. These are the fundic and pyloric chambers.

Skin

  • The skin of dolphins is very important as it is specialized to satisfy specific requirements.
  • The skin of a dolphin is made up of two parts: the epidermis and the blubber, which consists of two layers including the dermis and subcutis.
  • The dolphin’s skin is known to have a smooth rubber texture and is without hair and glands, except mammary glands. 
  • The thickness of a dolphin’s epidermis differs, depending on species and age.

Blubber

  • Blubber is found within the dermis and subcutis layer and this fat is thickest on the dolphin’s back and belly.
  • The thickness of the subcutaneous blubber or fat depends on things like the dolphin’s health, location, development, reproductive state, and how well it feeds. 
  • Blubber is different from fat in that, in addition to fat cells, it contains a fibrous network of connective tissue.
  • Blubber also functions to streamline the body and form structures such as the dorsal fin, propulsive fluke blades, and caudal keels.
  • Blubber helps the dolphin stay warm. 
  • When temperatures drop, the blubber constricts the blood vessels to reduce blood flow in the dolphin.
  • This allows the dolphin to spend less energy heating its body, ultimately keeping the animal warmer without burning energy.

Senses

Ear

  • The dolphin ear has specific adaptations to the marine environment. 
  • In dolphins, there is not much difference between the inner and outer environments. Sound does not pass through the outer ear to the middle ear. Instead, dolphins receive sound through the throat, after which it passes through a low-impedance fat-filled cavity to the inner ear. 
  • Dolphin ears are acoustically isolated from the skull by air-filled sinus pockets, which allow for greater directional hearing underwater.
  • Dolphins communicate by sending out high-frequency clicks from an organ known as a melon.

Eye

  • The dolphin eye is relatively small for its size, yet they have a good degree of eyesight. The eyes of a dolphin are placed on the sides of its head, so its vision consists of two fields, rather than a binocular view like humans have. 
  • When dolphins surface, their lens and cornea correct the nearsightedness that results from the refraction of light.
  • Most dolphins have slightly flattened eyeballs, enlarged pupils, and slightly flattened corneas.
  • They also have glands on the eyelids and an outer corneal layer that act as protection for the cornea.
  • The olfactory lobe and nerve are absent in dolphins, suggesting that they have no sense of smell.

Movement

  • Dolphins have two pectoral flippers, containing four digits, a boneless dorsal fin for stability, and a tail fin for propulsion. 
  • Dolphins swim by moving their tail fin and rear body vertically, while their flippers are mainly used for steering.
  • Dolphins are fast swimmers and typically cruise at 9–28 km/h (5.6–17.4 mph).
  • The orca, however, can travel at speeds up to 55.5 km/h (34.5 mph). 

Behavior and Intelligence

  • Dolphins are highly social animals, often living in pods of up to a dozen individuals.
  • Pod sizes and structures vary greatly between species and locations. 
  • A superpod may contain as many as 1,000 dolphins. 
  • Membership in pods is not rigid and interchange is common. 
  • Dolphins will stay with injured or ill members, helping them to breathe by bringing them to the surface if needed.
  • Dolphins have been seen protecting swimmers from sharks by swimming circles around the swimmers or charging the sharks to make them go away.
  • Dolphins communicate using a variety of clicks, whistle-like sounds and other vocalizations.
  • Dolphins frequently leap above the water surface and this is done for many different reasons. 
  • When moving, jumping can save the dolphin energy as there is less friction while in the air.
  • Dolphins show many types of playful behavior, often including objects like self-made bubble rings.
  • When playing with objects or small animals, common behavior includes carrying the object or animal along using various parts of the body, passing it along to other members of the group or taking it from another member, or throwing it out of the water.
  • Playful dolphin interactions with humans are the most obvious examples.
  • Dolphins engage in acts of aggression towards each other. The older a male dolphin is, the more likely his body is to be covered with bite scars. 
  • Dolphins are known to teach, learn, cooperate, scheme, and grieve.

Feeding and Threats

Feeding

  • There are various feeding methods among and within species, some apparently exclusive to a single population. 
  • Fish and squid are the main food, but the orca also feed on other marine mammals. 
  • Dolphins have been known to follow seabirds, whales and fishing boats to feed on the fish the birds scare to the surface or discard.
  • Different breeds of dolphins vary widely in the number of teeth they possess.
  • While the bottlenose dolphin has anywhere from 72 to 116 conical teeth and its smaller cousin the common dolphin has 188-268 teeth, the orca usually carries 40-56 teeth.
  • A common feeding method is herding, where a pod squeezes a school of fish into a small volume, known as a bait ball. 
  • Individual members then take turns plowing through the ball, feeding on the stunned fish.
  • Dolphins chase fish into shallow water to catch them more easily. This is called corralling.
  • Some species also whack fish with their flukes, stunning them and sometimes knocking them out of the water.

Threats

  • Dolphins have few marine enemies.
  • For most of the smaller species of dolphins, only a few of the larger sharks, such as the are a potential risk, especially for calves.
  • Some of the larger dolphin species, especially orcas, also prey on smaller dolphins, but this seems rare.
  • Dolphins also suffer from a wide variety of diseases and parasites.
  • Dolphins can tolerate and recover from extreme injuries such as shark bites although the exact methods used to achieve this are not known. 
  • The healing process is rapid and even very deep wounds do not cause dolphins to bleed to death. 
  • Infection of even large wounds seems rare.
  • Heavy metals, plastics, pesticides, and many industrial and agricultural pollutants that do not disintegrate rapidly in the environment accumulate in dolphins.
  • Collisions with boats and propellers cause injuries or deaths in dolphins. 
  • Various fishing methods unintentionally kill many dolphins.  
  • In some parts of the world, dolphins are considered food and are killed in harpoon hunts.

Did You Know

  • Various species of dolphins are kept in captivity, in theme parks, commonly known as a dolphinarium.
  • Bottlenose dolphins are the most common species kept in dolphinariums. These species are relatively easy to train, have a long lifespan in captivity and have a friendly appearance. Thousands of bottlenose dolphins live in captivity across the world, though exact numbers are hard to determine. 
  • The orca’s intelligence, trainability, striking appearance, playfulness, and sheer size have made it a popular exhibit at aquaria and aquatic theme parks
  • Dolphins are an increasingly popular choice of animal-assisted therapy for psychological problems and developmental disabilities.

Dolphin Worksheets

This bundle contains 11 ready-to-use Dolphin Worksheets that are perfect for students who want to learn more about Dolphins which are highly intelligent marine mammals that live in water but breathe through a blowhole on the top of their head. They are remarkable creatures that have developed a form of sonar called echolocation to hunt and prey.

Download includes the following worksheets:

  • Dolphin Facts
  • Dolphin Word Search
  • Fact Check
  • Synonym, Antonym
  • Mating Season
  • Word Wave
  • Dolphins at Risk
  • Dolphin Slogan
  • Family Portrait
  • Dolphin Crossword Puzzle
  • If I Were a Dolphin

Frequently Asked Questions

What are baby dolphins called?  

A baby dolphin is called a calf. 

What noise do dolphins make?  

Dolphins make two kinds of sounds, “whistles” and “clicks”. 

What is a group of dolphins called?  

A group of dolphins is called a pod.

How many years do dolphins live?  

Dolphins live between 40-60 years.

Can you eat dolphin meat? 

Dolphin meat can be high in mercury and may pose a health danger to humans.

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Use With Any Curriculum

These worksheets have been specifically designed for use with any international curriculum. You can use these worksheets as-is, or edit them using Google Slides to make them more specific to your own student ability levels and curriculum standards.

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