An adult dolphin's diet includes fish as well as other seafood like squid, shrimp or (on Pern) spiderclaws and drowned Thread. Dolphins do not need to drink freshwater as they get the water they need through their food.

Although successful as solitary hunters, dolphins often hunt cooperatively and show a wide array of strategies with some pods developing specialized traditions depending on their habitat. These include herding fish into tidal flats up to the point where the dolphins beach themselves to catch the stranded fish, corralling fish by encircling them and trapping them against the water surface, fluke-splashing the water surface to startle fish out of hiding places in shallow waters, stunning fish by sonar bombardment or fluke-whacking, the use of tools to flush out hidden prey, and cooperating with human fishermen.

Dolphins have only one set of evenly cone-shaped teeth for their whole life. The teeth break through around the fifth to sixth week after birth. They are used predominantly to catch and hold the prey, which is then usually swallowed whole or in chunks. It is possible to tell a dolphin's age by counting the rings on its teeth, similar to counting the rings on a tree trunk. In older dolphins, the teeth might be worn down, making it hard for the dolphin to hunt successfully.

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Dolphins do not sleep like we do. They are 'conscious breathers' who, unlike humans, need to stay awake to keep breathing. (This is also the reason why they cannot be anaesthetized.) If they need to rest, they float close to the water surface, sometimes swimming along very slowly, and one side of their brain always stays awake to control breathing while the other side relaxes. Often they will close one eye during these times. They nap like this for numerous short periods throughout the 24-hour cycle, in contrast to humans sleeping trough several hours at night.

Pern's dolphins have always been puzzled by the concept of the Great Sleep taught to them by their elders. The idea that their ancestors slept for fifteen years in cryogenic tanks before reaching the planet is as alien to them as the concept of space travel itself.

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Oceanic dolphins, such as the blue and bottlenosed dolphins brought to Pern, can see equally well under water as above water, but only with very limited color vision. Their eyes are highly sensitive to the blue part of the color spectrum and possess "mirror cells" to amplify the low light levels at night or in deep water, giving them the appearance to glow like feline eyes in the dark. Their pupils can open and close independently from each other so that a dolphin swimming on its side can keep one eye on the dark ground below while the other is scanning the bright sky above and see equally well with both at the same time. Under water and at night, a dolphin's vision is far superior to human eyes.

Dolphins are also capable of 'seeing' their surroundings even in complete darkness through sound echoes reflected off obstacles in the water. They use this sonic radar to locate prey or navigate through murky waters, and supersonic bursts to stun fish. The dolphins of Pern also use their sonar to assist healers in detecting pregnancies, broken bones, or tumors in human patients. The sounds made by a dolphin during echolocation sound like rapid clicks to the human ear. Many of the ultrasounds produced by dolphins however are inaudible for humans.

Besides sight and sound, dolphins might be able to sense changes in water pressure and currents through their sensitive skin as well as sense magnetic fields to help them navigate on a global scale. Dolphins have no sense of smell, but can taste differences in water composition.

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Dolphins are born tail-first after a pregnancy that lasts about twelve months. Newborn calves are usually about a third of the length of their mothers. Twins are extremely rare. A newborn dolphin synchronizes its swimming and breathing patterns with its mothers and swims at her side for the first few weeks. Once the calf grows older, synchrony declines and it swims preferably underneath its mother. For the first six to twelve months after birth, the calf feeds exclusively on its mother's rich milk. Even after starting to eat fish, it continues nursing for at least another year (sometimes for as long as eight years) and stays with its mother for at least three to five years.

Female dolphins usually become reproductively active between the ages of ten and thirteen years, with some females starting as early as five to six years of age. (Such early pregnancies often cause problems, as the female is not yet fully grown.) The males usually mature between twelve to fourteen years of age, with the quicker ones becoming active around eight to nine years of age. Due to the long calf-rearing times, females breed only every few years and after weaning their previous calf. They are receptive about twice to seven times a year, with peak times for mating and birthing in spring and fall.

The average dolphin lifespan is forty to fifty years, with females having a longer life expectancy than males. The age range for Pernese dolphins might be higher, due to the pre-selection of genetically unimpaired individuals to accompany the settlers combined with the unpolluted oceans on Pern. (We can see a similar effect in Pern's human population during Intervals.)

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Female dolphins and their calves form family groups (pods) in which many of the females are related to each other. These pods are dynamic and include typically around twelve to fifteen individuals, but can grow as large as forty members. Occasionally, dolphin pods will gather to form large schools of five hundred or more dolphins of both genders and all ages. On Pern, these gatherings would happen during the times when the youngsters attempt to cross the Subsidence (see below under Dolphin Traditions on Pern).

Dolphin calves stay with their mothers for at least three to five years. Over time, they increasingly socialize with other calves and females of all ages, but not with older males. (Male dolphins generally play little part in rearing their calves. The mother dolphins actually try to keep the more aggressive adult males away from their young.) This childhood time is important for the young dolphins to learn social and feeding skills in the safety of their mother's pod. Dolphins in this age range are rarely able to fend for themselves without the help of others.

Juvenile dolphins of both genders frequently leave the mother/calf nursery pods for extended periods of time, forming their own groups until they become sexually mature. Female dolphins usually rejoin their mothers' pod whereas males remain with other males in rowdy bachelor groups.

Mature males often form a lifelong cooperative coalition with another male of similar age. These alliances are more than just hunting partnerships. Males usually compete aggressively over females, so cooperating with a partner in gaining and defending access to receptive females is of significant advantage to both. The bond formed between two males in an alliance is extremely strong (second only to the mother/calf bond) and the longest lasting type of relationship known in dolphin communities. Thus, young males in search of an alliance partner are probably the most likely candidates for forming stable partnerships with human dolphineers on Pern.

Dolphins are promiscuous and don't choose a mating partner for life. Courtship usually involves the male(s) following a receptive female around, "sweet-talking" her with pulsed yelps and popping sounds. They will try to impress her by posturing, jaw clapping and body contact. If she is willing, she will roll onto her side to present her underside. The actual mating is short and always takes place underwater in a belly-to-belly position. A receptive female might mate with several males during her cycle.

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Dolphins are playful and enjoy a very active social life. They utilize a wide range of body language to communicate their feelings, such as jaw clapping to indicate annoyance, flipper slapping or lobtailing (slapping their flukes on the water) to signal anger, presenting their underside, rolling their eyes, body twists, head nodding and shaking.

Touch plays an important role in dolphin-dolphin interactions. Young calves stay in close contact to their mothers. Dolphins often deliberately brush against each other, using their flippers or beaks to stroke or nuzzle each other. Two dolphins meeting each other often rub their pectoral fins together as a form of greeting (a delphinic hug or handshake so-to-speak). Dolphins might also "hold hands" while swimming, indicating their friendship. Aside from friendly contact, dolphins also use touch in aggressive ways in the form of biting, tooth-raking, head-butting and ramming.

Aside from body language, dolphins are very vocal creatures. Delphinic speech consists of all kinds of barks, squeaks, pops, moans, clicks, squees, trills, croaks, grunts and other sounds. In the club, delphinic speech is noted using ^^...^^ quotes (in contrast to dolphins using human speech, which is noted as "...").

Each dolphin has its own delphinic name in the form of a so-called "signature whistle". Dolphin calves learn their whistle from their mother. A good listener with knowledge of delphinic whistles might be able to tell from an individual's signature whistle in which pod that dolphin was born. The whistles can change over time. For example, the signature whistles of male dolphins often converge once they form an alliance, indicating their partnership. Dolphins interacting with humans learn their human partners' signal whistles.

It is possible for humans to learn to interpret delphinic speech. However, the mentasynth treatment also enabled the dolphins to learn, understand and use human speech. Pernese dolphins adopted names pronounceable in human language and formed the tradition of passing them on to their offspring. Thus, each dolphin on Pern also has a name in human speech aside from its delphinic whistle. Dolphins speaking human speech usually use simple, short sentences with many repetitions.

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Dolphin song has the capacity to travel for nearly a hundred miles. By relaying a message through a chain of pods, dolphins can quickly exchange news over long distances. A more specialized form of dolphin long-range communication is "sounding" (undersea sound waves) through sound channels. This technique enables dolphins to send supersonic messages over thousands of miles.

The speed of sound under water is a function of temperature, salinity and pressure. Due to the temperature and pressure profile in the ocean, deep-sea "superhighways" trap and submit sound over long distances by acting like a lens in focusing and guiding sound waves. These deep-sea sound channels vary in depth depending on season, geography and weather, but are generally accessible to diving dolphins around upwellings, colder waters and higher latitudes (for example around the Great Subsidence). Aside from the open ocean, shallow waters (for example in bays) are also capable of forming such sound channels, depending on the structure of the seabed.

Some of Pern's dolphins always stay in these areas and serve as sounders, receiving and spreading messages between the pods.

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Pern's dolphins are the descendants of twenty-five blue and bottlenosed dolphins - ten males and fifteen females - who reached Pern with the original colonists in cryogenic freeze tanks on the spaceship Bahrain. They were volunteers who had agreed to the Dolphin Contract (see below). Some dolphins chose to permanently pair up with a human dolphineer as rescue teams. The centerpiece of human/dolphin communication is the dolphin bell, situated so that members of both species can ring it. The original bell was located at Monaco Bay.

The first pod leader was a blue named Theresa, who later became known as the "Tillek". As the dolphin population grew, new pods formed and spread over Pern, each of them led by a senior female. The pods adopted names from the original geographic names used by the settlers (Monaco Pod, Kahrain Pod etc).

When Thread fell for the first time, the dolphins could not understand why humans had to protect themselves against it. Thread drowns in water, so it is much less harmful for sea creatures like dolphins and actually is eaten by many of them. Most dolphins think of Thread as a tasty snack.

With the imminent explosion of Mount Garben above Landing, dolphins assisted in the Dunkirk Crossing. When much of the cargo was blown off the ships by gale-force winds, the dolphins helped in rounding up and moving lost containers. This was the last major teamwork between dolphins and humans in Pern's early history. After the migration of the humans to the northern continent and their decimation by a plague, the contact between dolphins and humans deteriorated. By the end of the first century after Landing, Pern's humans had all but forgotten about the Dolphin Contract. But the dolphins never forgot and always kept their side of the bargain.

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Dolphins must:

1. Answer the call of the sea-bell when it rings.
2. Guard human beings on or near the water, to the best of their abilities, even to the cost of their own lives.
3. Assist in all sea rescues of humans.
4. Inform humans of oncoming sea hazards, including the presence of dangerous sea creatures.
5. Aid humans with their abilities to detect earthquakes and track tsunami waves.
6. Upon request, spot schools of food fish and inform fishing boats where they are to be found.

In an honorary capacity, dolphins also escort the bodies of the human dead, buried at sea, to their final resting place.

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After learning human speech, the dolphins adopted the names they had been given and formed a tradition of passing them on to their offspring. Many of these names were originally taken from places and historical figures on Earth (for example Amadeus, China, Oregon, Theresa). They have been set to dolphin music, and this Name Song is sung at special occasions and on longer journeys in the Great Currents. Pernese dolphins use human speech not only to communicate, but also in their Songs, which are sung to entertain as well as inform, just like the Teaching Ballads of the human Harpers.

To honor Captain Jim Tillek, the pods adopted the name "Tillek" for the acknowledged leader of all dolphins on Pern. This tradition has been handed down until the present day. It is the Tillek's responsibility that all young dolphins learn Speech and know their duties towards the humans on Pern and the meaning of the ringing sequences of the sea-bell. She will firmly discipline dolphins who are disrespectful towards humans or question the Dolphin Contract. The Tillek is also the keeper of dolphin history and hands it on to the next generation. With the Songs, dolphin history is taught in human speech. Young dolphins will first be taught by their mothers, then by their pod leaders, and finally be chosen to travel to the Northwest Sea to be taught by the Tillek herself.

Dolphins gather annually around Turnover in the Northwest Sea east of the Western Continent to exchange news and train the young. Although the pods are autonomous, they assist each other and hold friendly competitions among themselves to help keep them sharp. The probably most important of those dolphin traditions is the swimming of the Great Subsidence. This is a right of passage all young males must go through to complete their training with the Tillek. The big challenge takes place in a treacherous whirlpool in the arctic waters northwest of High Reaches Head, although some use the smaller subsidence in the Eastern Sea. Considered challenging, exhilarating and dangerous, it is not witnessed by humans.

Before the young dolphins attempt to cross the Subsidence, the Name Song is sung in its entirety, giving honors to those dolphins that arrived with the settlers. Then the young males have to prove themselves by swimming many hours and dragonlengths across the great whirlpool of the Subsidence, fighting against a vicious undertow threatening to yank them down. It requires strength, timing and daring, and not everyone who tries makes it. It is suspected that when a dolphin is killed during this ritual, his death is explained as "unknown."

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