Dolphins and porpoises are both cetaceans, marine mammals that are close cousins with whales. Dolphins are a member of the Delphinidae family and are as big as 30 feet long.
Porpoises, belonging to the Phocoenidae family, are stout and smaller, with other anatomical differences.
Even though both animals are extremely intelligent, dolphins are considered to be more social and live in larger and more stable groups.
Although “porpoise” and “dolphin” are often used interchangeably. The term porpoise should be used in reference only to the Phocoenidae family, in which there are a total of seven porpoise species.
Dolphins are more common than porpoises. Most scientists have agreed that there are a total of 32 dolphin species (plus five that are closely related species of the river dolphin) and only about six porpoise species.
What is the difference between dolphins and porpoises?
The difference between dolphins and porpoises essentially comes down to their facial structure ( I mean no person can easily forget Flipper’s famous “grin”), their figures, as well as their fins.
Dolphins are known to have elongated beaks that are prominent, as well as cone-shaped teeth. On the other hand, porpoises have smaller mouths and teeth shaped like a spade.
The dolphins have a hooked or curved dorsal fin (which is the one located in the middle of the animal’s back), but the porpoise has a triangular dorsal fin. Speaking in general terms, we can say that the dolphin bodies are leaner, while the porpoises’ are portly.
Another interesting difference is that dolphins are known to be more vocal than porpoises. Dolphins are very interactive as they make whistling sounds via their blowholes as a way of communicating with one another underwater.
Scientists are almost certain that porpoises do not make this communication pattern, and some assume that this may be a result of structural differences in the blowhole of the porpoise.
Dolphins and porpoises also have many similarities, one of which is their outstanding intelligence.
Both animals have large and complex brains. They also boast of a structure in their foreheads, known as the melon, with which they are able to generate sonar (sound waves), which helps them to navigate their underwater world.
Dolphin vs. Porpoise Anatomy
The main differences between porpoises and dolphins are anatomical, as mentioned earlier. Externally, anyone can tell the difference between both two animals by looking at the head and dorsal fins.
Dolphins normally have a “beak” that makes them appear “long-nosed,” while porpoises do not have a beak and thus appear more “flat-faced.”
The dorsal fins on dolphins are usually curved or hooked, while those on porpoises are more triangular in shape.
Up close, one can distinguish the two by their teeth: dolphins have cone-shaped teeth, but porpoises have flat or spade-shaped teeth.
Dolphins and porpoises come in varying sizes, with dolphins generally appearing as the larger of both aquatic animals.
The killer “whale” or orca, which is actually a dolphin, genetically, can grow to sizes of up to 35 feet in length, for instance, and Hector’s dolphin, which is found in New Zealand sometimes grows bigger than 4 feet. On average, porpoises, which appear more darkly-colored than dolphins, grow to between 5 and 8 feet in length.
Both species of mammals breathe air via the blowholes located at the top of their head. And, just like almost all other mammals, these two animals give birth to their young lives and also nurse their offspring.
Porpoises and dolphins even have hair, but almost all of their hair is lost shortly after they are born.
Of the three types of fins that can be found on porpoises and dolphins, only the flippers (pectoral fins), which function as tools for stopping and steering underwater, have bones.
These unique fins contain the exact same number of bones that are contained in a human arm and also end in five digits that are aligned similarly to fingers. Scientists have theorized that these bones evolved from the ancient land-dwelling ancestors of dolphins and porpoises some 50 million years ago.
Beyond the dorsal, the pectoral fins, or back provides stability as the porpoise and dolphin move swiftly through water (up to 25 mph).
This dorsal fin, together with the tail flukes, is made of pure collagen, a fibrous connective tissue that is similar to cartilage.
The use of Echolocation and Other Senses
Both porpoises and dolphins make use of echolocation to find food, navigate underwater, avoid predators, and also communicate with other members of their species.
They also have a small external ear opening that is located about two inches behind the eye in the porpoise and dolphin. Neither porpoises nor dolphins rely specifically on their sense of smell.
However, vocalizations are more frequent and extensive with dolphins, and these sounds can travel longer distances than the sounds recorded for porpoises.
Males of both porpoises and dolphins feature two genital openings located on their ventral side, while the females have four.
Two out of the female’s four openings are their sex organs, and the other two are for lactation, with their teats located inside the body.
The mating seasons for both porpoises and dolphins tend to be short, with the dominant males having multiple mates. Pair bonding is not common in porpoises but is more frequently observed in dolphins, and this union is often one that lasts for life.
Gestation periods for both animals are very similar, and that lasts between 7 and 12 months, with the birth of 1-2 calves born, though the births are most often single ones. Calves for both dolphins and porpoises are weaned after about a year.
Social Behavior of Dolphins and Porpoises
Dolphins have been found to live in pods, or small groups, of up to 12 individuals. Where there is an abundance of food. However, “superpods” which is a collection of over 1,000 dolphins have been noticed.
Dolphins carry out hunts and also communicate for other reasons by making a combination of clicks, whistles, and ultrasonic sounds.
Porpoises are a somewhat relatively shy animal and are seen roaming alone or in small groups containing a few individuals.
It is quite rare to find them in large pods. Their grouping behavior also does not lead to any stable associations, but there are ephemeral relationships that will change as individuals leave or join.
Porpoises can function in a coordinated fashion even in cases where they are hundreds of feet away from each other, using echolocation for locating prey and staying together in the same pod but do not use echolocation to communicate as often as their dolphin cousins do.
Dolphin vs. Porpoise Intelligence
Dolphins and porpoises are both highly intelligent mammals. They have brains that are large and complex, and both animals are self-aware, just like humans.
These animals are among the few species in the waters and the world as a whole that can identify themselves in a mirror.
Several years of research have given scientists the chance to make an extensive case for offering protection to cetaceans (including dolphins, porpoises, and whales) from unrestricted hunts and fishing.
This and the risk of potential extinction are a few of the reasons for international bans on dolphin and whale hunting, as well as the prohibition of net-based tuna fishing, which could lead to the trapping and drowning of dolphins.
The Bottlenose dolphin has been noticed and recorded as they call out the specific names of others of their kind when they are separated. Apart from humans, dolphins are the only animals that are known to explicitly call other members of their species by name.
Dolphins have also been seen caring for injured members of their species and also helping humans adrift at sea.
Because they have been found to be more gregarious, dolphins are now popular animals for training in captivity, which is a situation that porpoises do not adapt to effectively.