Speaker 1: Welcome to the I Can't Sleep Podcast, where I help
Speaker 1: you drift off one fact at a time. I'm your host,
Speaker 1: Benjamin Boster, and today's episode is about dolphins. Dolphins belong
Speaker 1: to a surprisingly large family, forty living species to be exact,
Speaker 1: spread across five different taxonomic families. There are the oceanic dolphins,
Speaker 1: the family most of us picture, and then four families
Speaker 1: of river dolphins adapted to fresh water and brackish environments
Speaker 1: from the Amazon to the Ganges. One of those river families,
Speaker 1: the Baiji or Chinese river dolphin, appears to have slipped
Speaker 1: into extinction sometime in the early two thousands. All of
Speaker 1: them fall under the larger category of two sed whales,
Speaker 1: which means they share evolutionary lineage with belugas, narwhales, porpoises,
Speaker 1: sperm whales, and beaked whales. The size range is staggering.
Speaker 1: At the small end, there's Maui's dolphin, barely longer than
Speaker 1: a tall human about five and a half feet and
Speaker 1: weighing about fifty kilograms. At the other extreme sits the orca,
Speaker 1: the apex predator of the group, stretching past nine meters
Speaker 1: and tipping the scales at ten tons. Sexual dimorphism shows
Speaker 1: up in many species, with males generally larger than females.
Speaker 1: What they all share is that torpedo shape, streamlined bodies,
Speaker 1: fore limbs evolved in the flippers. No external hind limbs
Speaker 1: to speak of, just vestigial pelvic bones tucked inside and
Speaker 1: a horizontal tail fluke that drives them forward. They're faster
Speaker 1: and more agile than seals, though not quite as flexible.
Speaker 1: Some dolphins hit brief bursts of twenty nine kilometers per hour,
Speaker 1: and they can leap nine meters into the air. Their
Speaker 1: conical teeth are built for grabbing fast moving prey, fish, squid, shrimp.
Speaker 1: Earing is exceptionally well developed, adapted for both air and water,
Speaker 1: so refined that some blind dolphins manage to survive. Certain
Speaker 1: species dive to great depths. They all carry a thick
Speaker 1: layer of blubber under the skinned, insulid against cold water.
Speaker 1: Dolphins live mostly in open ocean, though some thrive in
Speaker 1: rivers and coastal zones. Most prefer warm tropical waters, but
Speaker 1: a few species, like the right whale dolphin, favor colder climates.
Speaker 1: They are carnivores, feeding largely on fish and squid, though
Speaker 1: the larger species or cans, especially go after seals or
Speaker 1: other dolphins, large fish like sharks and tuna, even sea
Speaker 1: birds on occasion. Males made with multiple females each year.
Speaker 1: Females only reproduce every two to three years. Calves arrive
Speaker 1: in spring and summer, and mothers shoulder all the caregiving.
Speaker 1: In some species, mothers fast while nursing for an extended stretch.
Speaker 1: Social complexity defines dolphin life. They live in what researchers
Speaker 1: call fissi and fusion societies, fluid groups or pods that
Speaker 1: constantly shift in size and membership. Communication happens through a
Speaker 1: variety of vocalizations, high pitched clicks, whistles, burst pulse sounds.
Speaker 1: Echolocation lets them navigate and hunt with precision. The name
Speaker 1: dolphin traces back to ancient Greek delphus, related to delphas,
Speaker 1: meaning womb. The idea was something like a fish with
Speaker 1: a womb, and early recognition that these animals didn't quite
Speaker 1: fit the usual categories. The word traveled through Latin Delphinus
Speaker 1: into Medieval Latin as dolphinus, then into Old French as dauphin,
Speaker 1: which eventually gave English the spelling we used today. In
Speaker 1: some older English dialects, they were called mere swine or seapig.
Speaker 1: Usage of the term can be a little loose. Dolphin
Speaker 1: generally covers most species in the oceanic dolphin family and
Speaker 1: the river dolphin families. Meanwhile, the Mahimahi fish is sometimes
Speaker 1: called dolphinfish, which adds a layer of confusion. In every
Speaker 1: day speech, people use whale for the larger cetaceans and
Speaker 1: dolphin for the smaller beaked ones, though that's not a
Speaker 1: strict biological line. The bottle nosed dolphin is so familiar
Speaker 1: that dolphin often means that species by default. Interestingly, six
Speaker 1: species commonly thought of as whales, orcas, melon headed whales,
Speaker 1: pygmy killer whales, false killer whales, and two species of
Speaker 1: pilot whales are actually classified as dolphins. Porpoises, by contrast,
Speaker 1: belong to a different family entirely. They have shorter beaks,
Speaker 1: spade shaped teeth, and different behavior patterns. A group of
Speaker 1: dolphins is a school or a pod. Males are bulls,
Speaker 1: females are cows, young ones are calves. The dolphin lineage
Speaker 1: reaches back to land dwelling mammals around forty eight million
Speaker 1: years ago. Their ancestors split off from a group that
Speaker 1: included the Indohias, an extinct Chevrotaine like ungulate sink of
Speaker 1: a small deer like creature. The earliest cetaceans, the Archaeocides,
Speaker 1: took to the water around forty nine million years ago
Speaker 1: and became fully aquatic within five to ten million years.
Speaker 1: The fossil record shows a gradual transformation. Ambulacetas around forty
Speaker 1: nine million years ago developed a hearing system that channeled
Speaker 1: vibrations from the jaw to the inner ear. Protocetas about
Speaker 1: forty three million years ago showed a streamlined body and
Speaker 1: tail flukes. Basilosaurus thirty five million years back had nasal
Speaker 1: openings migrating toward the top of the skull and four
Speaker 1: limbs modified into flippers. By thirty four million years ago,
Speaker 1: hind limbs were shrinking and eventually disappeared in the first
Speaker 1: true toothed and baling whales. Modern dolphins still carried two
Speaker 1: small rod shaped pelvic bones, remnant of that terrestrial past. Today,
Speaker 1: the closest living relatives of cetaceans are hippopotamuses. They share
Speaker 1: a semi aquatic ancestor from about sixty million years ago
Speaker 1: around forty million years ago, the lineage split. One branch
Speaker 1: became cetaceans, the other became anthricothars, which when extinct at
Speaker 1: the end of the Pleistocene, leaving only hippos behind. Dolphin
Speaker 1: anatomy is a study in adaptation. Torpedo shaped bodies, non
Speaker 1: flexible necks, limbs turned to flippers, a tail fin, and
Speaker 1: a bulbous head. The skull has small eye sockets, a
Speaker 1: long snout, and eyes set on the sides no external
Speaker 1: ear flap. Size varies widely, from the tiny Maui's dolphin
Speaker 1: to the massive orca. Several species show female biased size differences,
Speaker 1: with females larger than males. Conical teeth, unlike the spade
Speaker 1: shaped teeth of porpoises, are designed for catching swift prey.
Speaker 1: Breathing involves expelling stale air through the blowhole in an
Speaker 1: upward blast, then inhaling fresh air. The spouts are small
Speaker 1: and not especially distinctive. Blubber thickness varies with climate. It
Speaker 1: provides buoyancy, some protection from predators and energy reserves, but
Speaker 1: its main job is insulation. Calves are born with a
Speaker 1: thin layer that sickens at different rates depending on where
Speaker 1: they live. The skin is specialized for protection, fat storage,
Speaker 1: heat regulation, and sensory perception. It's made of an outer
Speaker 1: epidermis and an inner layer of blubber, which includes the
Speaker 1: dermis and subcutis. Dolphins skin is a smooth, almost rubbery texture.
Speaker 1: There's no hair and no glands except for memory glands.
Speaker 1: Newborns have a line of hairs on both sides of
Speaker 1: the rostrum. The jaw about sixteen to seventeen centimeters in
Speaker 1: total length. The epidermis lacks carat and features a complex
Speaker 1: innerweaving of structures that increase the surface area between skin layers.
Speaker 1: Thickness varies by species and age. Blubber sits within the
Speaker 1: dermis and subcutis. The boundary between dermis and fat layer
Speaker 1: is gradual, with collagen fibers running throughout. Thickness depends on health, development, location,
Speaker 1: reproductive state, and feeding success. Its thickest on the back
Speaker 1: and belly. Unlike simple fat, blubber contains a fibrous network
Speaker 1: of connective tissue. It streamlines the body and forms specialized
Speaker 1: structures like the dorsal fin and tail. Flukes. Nerve endings
Speaker 1: resembling small onion like configurations appear in the superficial dermas
Speaker 1: mechana receptors tucked into the interlocking ridges of skin layers.
Speaker 1: These nerve endings provide highly refined sensory perception, the body's
Speaker 1: ability to sense its own position and movement. Dolphins are
Speaker 1: sensitive to vibrations and small pressure changes. Blood vessels and
Speaker 1: nerve endings run through the dermis. In the dorsal fin,
Speaker 1: flukes and flippers, arteries and veins run parallel. Blubber manipulates
Speaker 1: blood flow to regulate temperature. When it's cold, the blubber
Speaker 1: constricts vessels to reduce blood flow and conserve heat. To
Speaker 1: release excess heat, Dolphins rely on thermal windows areas that
Speaker 1: lack blubber and are thin and highly vascularized, including the
Speaker 1: dorsal fin, flukes and flippers. They also use countercurrent heat exchange.
Speaker 1: Blood flowing in different directions transfers heat across membranes, so
Speaker 1: warm blood leaving the heart warms the cold blood returning
Speaker 1: from the extremities, keeping the core warm while minimizing heat
Speaker 1: loss to the water. Two pectoral flippers, each with four
Speaker 1: digits inside, a boneless dorsal fin for stability, a fluke
Speaker 1: for propulsion. Though they lack external hind limbs. Some individuals
Speaker 1: have small internal rem nants that may contain vestiges of
Speaker 1: feed and digits. Orcas are notably fast swimmers, up to
Speaker 1: fifty five kilometers per hour, compared to seals that typically
Speaker 1: cruise at nine to twenty eight kilometers per hour. A
Speaker 1: study of a Pacific white sided dolphin found it could
Speaker 1: accelerate from five meters per second and nearly nine meters
Speaker 1: per second in less than a second using just five strokes.
Speaker 1: The neck vertebrae are fused, which increases stability at high
Speaker 1: speed but reduces flexibility. Most dolphins can't turn their heads.
Speaker 1: River dolphins, on the other hand, have unfused vertebrae and
Speaker 1: can turn their heads up to ninety degrees. Dolphins swim
Speaker 1: by moving the tail, fluke, and rear body vertically. Flippers
Speaker 1: are mainly for steering. All species have a dorsal fin
Speaker 1: to prevent involuntary spinning. Some dolphins are adapted for deep dives.
Speaker 1: They can selectively slow their heart rate to conserve oxygen
Speaker 1: and reroute blood from pressure tolerant tissues to the heart, brain,
Speaker 1: and other vital organs. Hemoglobin and myoglobin store oxygen in
Speaker 1: body tissues. They have twice as much myoglobin as hemoglobin.
Speaker 1: Dolphin ears are specially adapted for the marine environment. In humans,
Speaker 1: the middle ear equalizes the impedance difference between air and
Speaker 1: the fluid filled cochlia. Dolphins don't face that problem. There's
Speaker 1: no great difference between the outer and inner environment. Sound
Speaker 1: reaches them through the throat, passing through a low embedance
Speaker 1: fat filled cavity to the inner ear. Air filled sinus
Speaker 1: pockets acoustically isolate the ear from the skull, improving directional hearing.
Speaker 1: Underwater dolphins generate sounds independently of breathing, using recycled air
Speaker 1: that passes through air sacs and structures called fauniclips sometimes
Speaker 1: called monkey lips. High frequency clicks pass through sound modifying
Speaker 1: fat bodies and the melon, a fatty structure in the forehead.
Speaker 1: The skull of any creature with a melon shows a
Speaker 1: large depression. This set up enables echolocation for orientation. Most
Speaker 1: dolphins don't have hair, but they do have hair follicles
Speaker 1: that may serve some sensory function. Echolocation not only locates objects,
Speaker 1: but also provides information about shape and size, Though the
Speaker 1: exact mechanism isn't fully understood. The small hairs on the
Speaker 1: rostrum of the bodo the South American river dolphin are
Speaker 1: thought to function as tactile sensors, possibly compensating for poor eyesight.
Speaker 1: Dolphin eyes are small relative to body size, but they
Speaker 1: retain good vision. Eyes, based on the sides of the
Speaker 1: head give two separate fields of view, rather than the
Speaker 1: binocular vision humans have. When dolphin's surface, the lens and
Speaker 1: cornea correct for the near sightedness caused by water's refraction
Speaker 1: of light. Eyes contain both rod and cone cells. They
Speaker 1: see in dim and bright light, but have far more
Speaker 1: rods than cones. They lack short wavelength sensitive pigments, meaning
Speaker 1: color vision is more limited than in most mammals. Most
Speaker 1: have slightly flattened eyeballs, enlarged pupils that shrink at the
Speaker 1: surface to prevent damage, slightly flattened corneas, and a tapatum
Speaker 1: lucidum reflective tissue behind the retina, all adaptations that let
Speaker 1: large amounts of light through and produce a very clear image.
Speaker 1: Glands on the eyelids in outer cornea protect the eye.
Speaker 1: The olfactory lobes and nerve are absent, suggesting dolphins have
Speaker 1: no sense of smell. Taste seems similarly limited taste buds
Speaker 1: or atropheed or missing. Still, some dolphins show preferences for
Speaker 1: certain fish, indicating at least some taste ability. Intelligence in
Speaker 1: dolphins is well documented. They teach, learn, cooperate, and show
Speaker 1: what looks like grief. The neocortex in many species contains
Speaker 1: elongated spindle neurons, cells that until two thousand seven were
Speaker 1: thought to exist only in great apes and humans. In humans,
Speaker 1: these neurons are involved in social conduct, emotions, judgment, and
Speaker 1: theory of mind. In dolphins, they appear in analogous brain regions,
Speaker 1: suggesting a similar role. Brain size was once considered a
Speaker 1: major intelligence indicator. Most of the brain maintains basic bodily functions,
Speaker 1: so a higher brain to body mass ratio may leave
Speaker 1: more brain available for complex cognition. Allimetric analysis shows that
Speaker 1: mammalian brain size scales at roughly the two thirds or
Speaker 1: three fourth power of body mass. Comparing an animal's actual
Speaker 1: brain size to the expected size yields an encephalisation quatient,
Speaker 1: another measure of intelligence. Orkis have the second largest brain
Speaker 1: of any animal, after sperm whales and some dolphins. A
Speaker 1: brain to body mass ratio is second only to humans.
Speaker 1: Self awareness is considered a marker of advanced abstract thinking,
Speaker 1: a precursor to processes like thinking about thinking. Research suggests
Speaker 1: cetaceans possess self awareness. The most common test is the
Speaker 1: mirror test. An animal is marked with temporary dye, then
Speaker 1: shown a mirror. If the animal uses the mirror to
Speaker 1: examine the mark, that's evidence of self awareness. Some researchers
Speaker 1: dispute these findings, arguing that the results are open to
Speaker 1: interpretation and susceptible to the clever Hans effect, the tendency
Speaker 1: to see intentional behavior where there may be none. The
Speaker 1: test is less definitive for cetaceans and for primates, since
Speaker 1: primates can touch the mark or the mirror, while cetaceans
Speaker 1: can only twist and turn to view it. Skeptics suggest
Speaker 1: behaviors interpreted as self awareness might just be social responses
Speaker 1: to another individual. Supporters counter that the behaviors are distinctly
Speaker 1: different from normal social responses. In nineteen ninety five, researchers
Speaker 1: use television to test dolphin self awareness, showing dolphins real
Speaker 1: time video of themselves, video of another dolphin, and recorded footage.
Speaker 1: They concluded the evidence suggested self awareness rather than social behavior.
Speaker 1: Since then, dolphins have passed the mirror test, though some
Speaker 1: researchers remain unconvinced. Dolphins are highly social, often living in
Speaker 1: pods of up to a dozen individuals. Those size and
Speaker 1: structure vary widely by species and location. In areas with
Speaker 1: abundant food, pods can merge temporarily into superpods that may
Speaker 1: exceed a thousand dolphins. Pod membership is fluid. Individuals move
Speaker 1: between groups. They form strong social bonds and will stay
Speaker 1: with injured or ill members, bringing them to the surface
Speaker 1: to breeze if needed. This altruism isn't limited to their
Speaker 1: own species. A dolphin named Mocho and New Zealand was
Speaker 1: observed guiding a stranded pygmy sperm whale and her calf
Speaker 1: out of shallow water. Dolphins have also been seen protecting
Speaker 1: human swimmers from sharks, either by swimming in circles around
Speaker 1: them or charging the sharks. Communication happens through clicks, whistle
Speaker 1: like sounds, and other vocalizations. Nonverbal communication includes touch and posturing.
Speaker 1: Dolphins display culture, something long thought unique to humans and
Speaker 1: perhaps other primates. In two thousand five, researchers in Australia
Speaker 1: found into Pacific bottle nosed dolphins teaching their young to
Speaker 1: use tools. They cover their snouts with sponges to protect
Speaker 1: them ale foraging. This knowledge is mostly passed from mothers
Speaker 1: to daughters, unlike in primates, where it's generally shared with
Speaker 1: both sexes. The sponge use is a learned behavior. Dolphins
Speaker 1: generally sleep with only one brain hemisphere and slow wave
Speaker 1: sleep at a time, maintaining enough consciousness to breathe and
Speaker 1: watch for threats. Earlier sleep stages can occur simultaneously in
Speaker 1: both hemispheres. In capacity, dolphins sometimes enter a fully asleep
Speaker 1: state with both eyes closed and no response to mild stimuli.
Speaker 1: Respiration becomes automatic. A tail kick preflex keeps the blowhole
Speaker 1: above water if necessary. Whether wild dolphins reach this state
Speaker 1: is unknown. The Indus river dolphin has a different sleep method.
Speaker 1: Living in water with strong currents and debris, it must
Speaker 1: swim continuously to avoid injury, so it leaps in very
Speaker 1: short bursts forward to sixty seconds at a time. Bottle
Speaker 1: nosed dolphins have signature whistles, unique sounds that function like names.
Speaker 1: These whistles identify individuals and are used to communicate over distance.
Speaker 1: A dolphin develops its signature whistle during its first year
Speaker 1: and maintains it for life. The development involves vocal production learning,
Speaker 1: influenced by interactions with other dolphins. Dolphins can address one
Speaker 1: another by mimicking a specific whistle. Male bottlenose whistles tend
Speaker 1: to resemble their mothers. Female whistles are more distinctive. Bottlenose
Speaker 1: dolphins have strong memories for these whistles. They can recognize
Speaker 1: the signature whistle of an individual they haven't encountered in
Speaker 1: over twenty years. Research on signature whistles and other species
Speaker 1: is limited and as yielded mixed results. Because dolphins travel
Speaker 1: in groups, communication is essential. Signal making occurs when similar
Speaker 1: sounds interfere with the original acoustic signal, and larger groups,
Speaker 1: individual whistles are less prominent. Dolphins travel in pods that
Speaker 1: range from a few individuals to many. Though they don't
Speaker 1: necessarily swim close to each other, they stay within the
Speaker 1: same general area. Higher whistle rates help prevent losing pod
Speaker 1: members when the group is spread out. Dolphins frequently leap
Speaker 1: above the water for various reasons. When traveling. Jumping saves
Speaker 1: energy less friction in the air. This is called porpoising.
Speaker 1: Other reasons include orientation, social displays, nonverbal communication, entertainment, and
Speaker 1: dislodging parasites. In the Port River north of Adelaide, several
Speaker 1: Indo Pacific bottle nosed dolphins have been seen tailwalking, a
Speaker 1: highly unusual behavior in the wild. This involves forcing most
Speaker 1: of the body vertically out of the water and may
Speaker 1: containing the position of vigorously pumping the tail, mimicking a
Speaker 1: standing posture, and moving backward along the water. The behavior
Speaker 1: started in nineteen eighty eight when a female named Billy
Speaker 1: was rescued after becoming trapped in a polluted marina. She
Speaker 1: spent two weeks recuperating with captive dolphins at a marine park,
Speaker 1: where she observed them tailwalking. After being returned to the
Speaker 1: Port River, she continued performing the behavior. Another dolphin wave
Speaker 1: copied her Wave. A very active tailwalker, passed the skill
Speaker 1: to her daughters, Ripple and Pilula. After Billy's early passing,
Speaker 1: Wave increased her tailwalking, and other dolphins in the group
Speaker 1: began performing it. By twenty eleven, up to twelve dolphins
Speaker 1: had been observed tailwalking, though only females appeared to learned.
Speaker 1: In October twenty twenty one, a dolphin was observed tailwalking
Speaker 1: for hours. Scientists find the spread of this behavior through
Speaker 1: up to two generations surprising, as it brings no apparent
Speaker 1: advantage and is very energy consuming. Dolphins can tolerate and
Speaker 1: recover from extreme injuries, though the exact mechanisms aren't known.
Speaker 1: Even large wounds restore in a way that preserves body
Speaker 1: shape and infection seems rare. A study published in Marine
Speaker 1: Mammals Science suggests that at least some dolphins serve live
Speaker 1: shark encounters using sophisticated maneuvers and cooperative tactics.