Using the terms dolphins and porpoises to describe marine mammals belonging to the Cetacean species [from the Greek “kenos” meaning large sea creature] are often used interchangeably. It’s a bit confusing, especially when you add whales to the mix — which in actuality is the largest member of the dolphin family. In fact, the Cetacean species consists of over 80 different marine mammals and is made up of all species of whale, dolphin and porpoise.
So what’s the differences between porpoises & dolphins?
For starters, dolphins are far more prevalent than porpoises. Most scientists agree that there are 32 dolphin species (plus five closely related species of river dolphins) and only six porpoise species.
According to the National Ocean Service, it essentially comes down to their faces. Who doesn't remember Flipper’s infamous “grin”?. Dolphins tend to have prominent, elongated “beaks” and cone-shaped teeth, while porpoises have smaller mouths and spade-shaped teeth. The dolphin’s hooked or curved dorsal fin (the one in the middle of the animal’s back) also differs from the porpoise’s triangular dorsal fin. Generally speaking, dolphin bodies are leaner, and porpoises’ are portly.
Dolphins are also more talkative than porpoises. Dolphins make whistling sounds through their blowholes to communicate with one another underwater. Scientists are pretty sure that porpoises do not do this, and some think this may be due to structural biological differences in the porpoise’s blowhole.
Dolphins and porpoises have many similarities, one of which is their high level of intelligence. Both have large, complex brains and a structure in their foreheads, called the melon, with which they generate sonar (sound waves) to navigate their underwater GPS world.
It is likely that more (or fewer) differences between dolphins and porpoises over time, and will be revealed as researchers continue to investigate these intriguing sentinels of the sea.
Now, what about whales?
With whales, the first thing to consider are the two different kinds of whales — baleen whales versus tooth whales. Baleen whales are what most people think of when they hear the word “whale”. Baleen whales do not have teeth and use their comb-like baleen to filter food out of the water.
Toothed whales are whales with, well, teeth. Dolphins and porpoises are both toothed whales, as well as orcas, (which are actually a kind of dolphin), sperm whales, beluga whales, and other whales such as pilot whales.
Can whales, dolphins and porpoise mate?
Scientists believe some actively try to mate outside their own species to increase the diversity of their wild populations.
Kekaimalu the 'wolphin' was the result of the union of a bottlenose dolphin and a killer whale, which is actually a member of the dolphin family. The two mated while working together at Sea Life Park in Hawaii and their progeny Kekaimalu was born in 1985. Her size - 600lbs and nearly 10ft long - and her color, and shape resemble both parents.
Unlike most hybrids, which tend to be sterile, Kekaimalu had two female calves, both sired by male bottlenoses.
There have also been unproven reports of wolphins being seen in the wild.
To date, dolphins are not known to mate with porpoises. In fact, there is scientific evidence that they don’t get a long at all. In Scotland, scientists found baby harbor porpoises washed up with horrific internal injuries. They thought the porpoises might have been killed by weapons tests until they found the toothmarks. Later, dolphins were caught on film crushing the baby porpoises. The dolphins even used their ecolocation to aim their blow at the porpoises' vital organs. Intraspecies love is complicated, don't you think?
Primary Source: Whales, Dolphins, and Porpoises