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<v Speaker 1>Welcome to the I Can't Sleep Podcast, where I help

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<v Speaker 1>you drift off one fact at a time. I'm your host,

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<v Speaker 1>Benjamin Boster, and today's episode is about dolphins. Dolphins belong

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<v Speaker 1>to a surprisingly large family, forty living species to be exact,

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<v Speaker 1>spread across five different taxonomic families. There are the oceanic dolphins,

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<v Speaker 1>the family most of us picture, and then four families

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<v Speaker 1>of river dolphins adapted to fresh water and brackish environments

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<v Speaker 1>from the Amazon to the Ganges. One of those river families,

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<v Speaker 1>the Baiji or Chinese river dolphin, appears to have slipped

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<v Speaker 1>into extinction sometime in the early two thousands. All of

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<v Speaker 1>them fall under the larger category of two sed whales,

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<v Speaker 1>which means they share evolutionary lineage with belugas, narwhales, porpoises,

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<v Speaker 1>sperm whales, and beaked whales. The size range is staggering.

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<v Speaker 1>At the small end, there's Maui's dolphin, barely longer than

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<v Speaker 1>a tall human about five and a half feet and

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<v Speaker 1>weighing about fifty kilograms. At the other extreme sits the orca,

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<v Speaker 1>the apex predator of the group, stretching past nine meters

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<v Speaker 1>and tipping the scales at ten tons. Sexual dimorphism shows

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<v Speaker 1>up in many species, with males generally larger than females.

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<v Speaker 1>What they all share is that torpedo shape, streamlined bodies,

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<v Speaker 1>fore limbs evolved in the flippers. No external hind limbs

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<v Speaker 1>to speak of, just vestigial pelvic bones tucked inside and

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<v Speaker 1>a horizontal tail fluke that drives them forward. They're faster

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<v Speaker 1>and more agile than seals, though not quite as flexible.

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<v Speaker 1>Some dolphins hit brief bursts of twenty nine kilometers per hour,

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<v Speaker 1>and they can leap nine meters into the air. Their

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<v Speaker 1>conical teeth are built for grabbing fast moving prey, fish, squid, shrimp.

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<v Speaker 1>Earing is exceptionally well developed, adapted for both air and water,

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<v Speaker 1>so refined that some blind dolphins manage to survive. Certain

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<v Speaker 1>species dive to great depths. They all carry a thick

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<v Speaker 1>layer of blubber under the skinned, insulid against cold water.

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<v Speaker 1>Dolphins live mostly in open ocean, though some thrive in

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<v Speaker 1>rivers and coastal zones. Most prefer warm tropical waters, but

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<v Speaker 1>a few species, like the right whale dolphin, favor colder climates.

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<v Speaker 1>They are carnivores, feeding largely on fish and squid, though

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<v Speaker 1>the larger species or cans, especially go after seals or

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<v Speaker 1>other dolphins, large fish like sharks and tuna, even sea

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<v Speaker 1>birds on occasion. Males made with multiple females each year.

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<v Speaker 1>Females only reproduce every two to three years. Calves arrive

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<v Speaker 1>in spring and summer, and mothers shoulder all the caregiving.

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<v Speaker 1>In some species, mothers fast while nursing for an extended stretch.

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<v Speaker 1>Social complexity defines dolphin life. They live in what researchers

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<v Speaker 1>call fissi and fusion societies, fluid groups or pods that

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<v Speaker 1>constantly shift in size and membership. Communication happens through a

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<v Speaker 1>variety of vocalizations, high pitched clicks, whistles, burst pulse sounds.

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<v Speaker 1>Echolocation lets them navigate and hunt with precision. The name

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<v Speaker 1>dolphin traces back to ancient Greek delphus, related to delphas,

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<v Speaker 1>meaning womb. The idea was something like a fish with

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<v Speaker 1>a womb, and early recognition that these animals didn't quite

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<v Speaker 1>fit the usual categories. The word traveled through Latin Delphinus

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<v Speaker 1>into Medieval Latin as dolphinus, then into Old French as dauphin,

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<v Speaker 1>which eventually gave English the spelling we used today. In

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<v Speaker 1>some older English dialects, they were called mere swine or seapig.

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<v Speaker 1>Usage of the term can be a little loose. Dolphin

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<v Speaker 1>generally covers most species in the oceanic dolphin family and

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<v Speaker 1>the river dolphin families. Meanwhile, the Mahimahi fish is sometimes

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<v Speaker 1>called dolphinfish, which adds a layer of confusion. In every

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<v Speaker 1>day speech, people use whale for the larger cetaceans and

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<v Speaker 1>dolphin for the smaller beaked ones, though that's not a

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<v Speaker 1>strict biological line. The bottle nosed dolphin is so familiar

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<v Speaker 1>that dolphin often means that species by default. Interestingly, six

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<v Speaker 1>species commonly thought of as whales, orcas, melon headed whales,

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<v Speaker 1>pygmy killer whales, false killer whales, and two species of

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<v Speaker 1>pilot whales are actually classified as dolphins. Porpoises, by contrast,

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<v Speaker 1>belong to a different family entirely. They have shorter beaks,

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<v Speaker 1>spade shaped teeth, and different behavior patterns. A group of

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<v Speaker 1>dolphins is a school or a pod. Males are bulls,

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<v Speaker 1>females are cows, young ones are calves. The dolphin lineage

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<v Speaker 1>reaches back to land dwelling mammals around forty eight million

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<v Speaker 1>years ago. Their ancestors split off from a group that

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<v Speaker 1>included the Indohias, an extinct Chevrotaine like ungulate sink of

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<v Speaker 1>a small deer like creature. The earliest cetaceans, the Archaeocides,

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<v Speaker 1>took to the water around forty nine million years ago

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<v Speaker 1>and became fully aquatic within five to ten million years.

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<v Speaker 1>The fossil record shows a gradual transformation. Ambulacetas around forty

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<v Speaker 1>nine million years ago developed a hearing system that channeled

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<v Speaker 1>vibrations from the jaw to the inner ear. Protocetas about

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<v Speaker 1>forty three million years ago showed a streamlined body and

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<v Speaker 1>tail flukes. Basilosaurus thirty five million years back had nasal

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<v Speaker 1>openings migrating toward the top of the skull and four

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<v Speaker 1>limbs modified into flippers. By thirty four million years ago,

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<v Speaker 1>hind limbs were shrinking and eventually disappeared in the first

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<v Speaker 1>true toothed and baling whales. Modern dolphins still carried two

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<v Speaker 1>small rod shaped pelvic bones, remnant of that terrestrial past. Today,

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<v Speaker 1>the closest living relatives of cetaceans are hippopotamuses. They share

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<v Speaker 1>a semi aquatic ancestor from about sixty million years ago

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<v Speaker 1>around forty million years ago, the lineage split. One branch

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<v Speaker 1>became cetaceans, the other became anthricothars, which when extinct at

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<v Speaker 1>the end of the Pleistocene, leaving only hippos behind. Dolphin

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<v Speaker 1>anatomy is a study in adaptation. Torpedo shaped bodies, non

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<v Speaker 1>flexible necks, limbs turned to flippers, a tail fin, and

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<v Speaker 1>a bulbous head. The skull has small eye sockets, a

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<v Speaker 1>long snout, and eyes set on the sides no external

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<v Speaker 1>ear flap. Size varies widely, from the tiny Maui's dolphin

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<v Speaker 1>to the massive orca. Several species show female biased size differences,

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<v Speaker 1>with females larger than males. Conical teeth, unlike the spade

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<v Speaker 1>shaped teeth of porpoises, are designed for catching swift prey.

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<v Speaker 1>Breathing involves expelling stale air through the blowhole in an

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<v Speaker 1>upward blast, then inhaling fresh air. The spouts are small

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<v Speaker 1>and not especially distinctive. Blubber thickness varies with climate. It

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<v Speaker 1>provides buoyancy, some protection from predators and energy reserves, but

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<v Speaker 1>its main job is insulation. Calves are born with a

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<v Speaker 1>thin layer that sickens at different rates depending on where

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<v Speaker 1>they live. The skin is specialized for protection, fat storage,

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<v Speaker 1>heat regulation, and sensory perception. It's made of an outer

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<v Speaker 1>epidermis and an inner layer of blubber, which includes the

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<v Speaker 1>dermis and subcutis. Dolphins skin is a smooth, almost rubbery texture.

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<v Speaker 1>There's no hair and no glands except for memory glands.

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<v Speaker 1>Newborns have a line of hairs on both sides of

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<v Speaker 1>the rostrum. The jaw about sixteen to seventeen centimeters in

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<v Speaker 1>total length. The epidermis lacks carat and features a complex

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<v Speaker 1>innerweaving of structures that increase the surface area between skin layers.

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<v Speaker 1>Thickness varies by species and age. Blubber sits within the

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<v Speaker 1>dermis and subcutis. The boundary between dermis and fat layer

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<v Speaker 1>is gradual, with collagen fibers running throughout. Thickness depends on health, development, location,

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<v Speaker 1>reproductive state, and feeding success. Its thickest on the back

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<v Speaker 1>and belly. Unlike simple fat, blubber contains a fibrous network

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<v Speaker 1>of connective tissue. It streamlines the body and forms specialized

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<v Speaker 1>structures like the dorsal fin and tail. Flukes. Nerve endings

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<v Speaker 1>resembling small onion like configurations appear in the superficial dermas

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<v Speaker 1>mechana receptors tucked into the interlocking ridges of skin layers.

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<v Speaker 1>These nerve endings provide highly refined sensory perception, the body's

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<v Speaker 1>ability to sense its own position and movement. Dolphins are

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<v Speaker 1>sensitive to vibrations and small pressure changes. Blood vessels and

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<v Speaker 1>nerve endings run through the dermis. In the dorsal fin,

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<v Speaker 1>flukes and flippers, arteries and veins run parallel. Blubber manipulates

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<v Speaker 1>blood flow to regulate temperature. When it's cold, the blubber

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<v Speaker 1>constricts vessels to reduce blood flow and conserve heat. To

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<v Speaker 1>release excess heat, Dolphins rely on thermal windows areas that

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<v Speaker 1>lack blubber and are thin and highly vascularized, including the

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<v Speaker 1>dorsal fin, flukes and flippers. They also use countercurrent heat exchange.

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<v Speaker 1>Blood flowing in different directions transfers heat across membranes, so

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<v Speaker 1>warm blood leaving the heart warms the cold blood returning

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<v Speaker 1>from the extremities, keeping the core warm while minimizing heat

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<v Speaker 1>loss to the water. Two pectoral flippers, each with four

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<v Speaker 1>digits inside, a boneless dorsal fin for stability, a fluke

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<v Speaker 1>for propulsion. Though they lack external hind limbs. Some individuals

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<v Speaker 1>have small internal rem nants that may contain vestiges of

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<v Speaker 1>feed and digits. Orcas are notably fast swimmers, up to

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<v Speaker 1>fifty five kilometers per hour, compared to seals that typically

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<v Speaker 1>cruise at nine to twenty eight kilometers per hour. A

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<v Speaker 1>study of a Pacific white sided dolphin found it could

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<v Speaker 1>accelerate from five meters per second and nearly nine meters

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<v Speaker 1>per second in less than a second using just five strokes.

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<v Speaker 1>The neck vertebrae are fused, which increases stability at high

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<v Speaker 1>speed but reduces flexibility. Most dolphins can't turn their heads.

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<v Speaker 1>River dolphins, on the other hand, have unfused vertebrae and

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<v Speaker 1>can turn their heads up to ninety degrees. Dolphins swim

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<v Speaker 1>by moving the tail, fluke, and rear body vertically. Flippers

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<v Speaker 1>are mainly for steering. All species have a dorsal fin

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<v Speaker 1>to prevent involuntary spinning. Some dolphins are adapted for deep dives.

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<v Speaker 1>They can selectively slow their heart rate to conserve oxygen

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<v Speaker 1>and reroute blood from pressure tolerant tissues to the heart, brain,

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<v Speaker 1>and other vital organs. Hemoglobin and myoglobin store oxygen in

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<v Speaker 1>body tissues. They have twice as much myoglobin as hemoglobin.

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<v Speaker 1>Dolphin ears are specially adapted for the marine environment. In humans,

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<v Speaker 1>the middle ear equalizes the impedance difference between air and

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<v Speaker 1>the fluid filled cochlia. Dolphins don't face that problem. There's

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<v Speaker 1>no great difference between the outer and inner environment. Sound

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<v Speaker 1>reaches them through the throat, passing through a low embedance

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<v Speaker 1>fat filled cavity to the inner ear. Air filled sinus

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<v Speaker 1>pockets acoustically isolate the ear from the skull, improving directional hearing.

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<v Speaker 1>Underwater dolphins generate sounds independently of breathing, using recycled air

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<v Speaker 1>that passes through air sacs and structures called fauniclips sometimes

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<v Speaker 1>called monkey lips. High frequency clicks pass through sound modifying

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<v Speaker 1>fat bodies and the melon, a fatty structure in the forehead.

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<v Speaker 1>The skull of any creature with a melon shows a

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<v Speaker 1>large depression. This set up enables echolocation for orientation. Most

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<v Speaker 1>dolphins don't have hair, but they do have hair follicles

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<v Speaker 1>that may serve some sensory function. Echolocation not only locates objects,

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<v Speaker 1>but also provides information about shape and size, Though the

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<v Speaker 1>exact mechanism isn't fully understood. The small hairs on the

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<v Speaker 1>rostrum of the bodo the South American river dolphin are

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<v Speaker 1>thought to function as tactile sensors, possibly compensating for poor eyesight.

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<v Speaker 1>Dolphin eyes are small relative to body size, but they

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<v Speaker 1>retain good vision. Eyes, based on the sides of the

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<v Speaker 1>head give two separate fields of view, rather than the

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<v Speaker 1>binocular vision humans have. When dolphin's surface, the lens and

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<v Speaker 1>cornea correct for the near sightedness caused by water's refraction

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<v Speaker 1>of light. Eyes contain both rod and cone cells. They

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<v Speaker 1>see in dim and bright light, but have far more

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<v Speaker 1>rods than cones. They lack short wavelength sensitive pigments, meaning

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<v Speaker 1>color vision is more limited than in most mammals. Most

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<v Speaker 1>have slightly flattened eyeballs, enlarged pupils that shrink at the

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<v Speaker 1>surface to prevent damage, slightly flattened corneas, and a tapatum

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<v Speaker 1>lucidum reflective tissue behind the retina, all adaptations that let

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<v Speaker 1>large amounts of light through and produce a very clear image.

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<v Speaker 1>Glands on the eyelids in outer cornea protect the eye.

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<v Speaker 1>The olfactory lobes and nerve are absent, suggesting dolphins have

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<v Speaker 1>no sense of smell. Taste seems similarly limited taste buds

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<v Speaker 1>or atropheed or missing. Still, some dolphins show preferences for

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<v Speaker 1>certain fish, indicating at least some taste ability. Intelligence in

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<v Speaker 1>dolphins is well documented. They teach, learn, cooperate, and show

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<v Speaker 1>what looks like grief. The neocortex in many species contains

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<v Speaker 1>elongated spindle neurons, cells that until two thousand seven were

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<v Speaker 1>thought to exist only in great apes and humans. In humans,

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<v Speaker 1>these neurons are involved in social conduct, emotions, judgment, and

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<v Speaker 1>theory of mind. In dolphins, they appear in analogous brain regions,

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<v Speaker 1>suggesting a similar role. Brain size was once considered a

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<v Speaker 1>major intelligence indicator. Most of the brain maintains basic bodily functions,

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<v Speaker 1>so a higher brain to body mass ratio may leave

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<v Speaker 1>more brain available for complex cognition. Allimetric analysis shows that

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<v Speaker 1>mammalian brain size scales at roughly the two thirds or

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<v Speaker 1>three fourth power of body mass. Comparing an animal's actual

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<v Speaker 1>brain size to the expected size yields an encephalisation quatient,

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<v Speaker 1>another measure of intelligence. Orkis have the second largest brain

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<v Speaker 1>of any animal, after sperm whales and some dolphins. A

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<v Speaker 1>brain to body mass ratio is second only to humans.

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<v Speaker 1>Self awareness is considered a marker of advanced abstract thinking,

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<v Speaker 1>a precursor to processes like thinking about thinking. Research suggests

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<v Speaker 1>cetaceans possess self awareness. The most common test is the

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<v Speaker 1>mirror test. An animal is marked with temporary dye, then

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<v Speaker 1>shown a mirror. If the animal uses the mirror to

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<v Speaker 1>examine the mark, that's evidence of self awareness. Some researchers

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<v Speaker 1>dispute these findings, arguing that the results are open to

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<v Speaker 1>interpretation and susceptible to the clever Hans effect, the tendency

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<v Speaker 1>to see intentional behavior where there may be none. The

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<v Speaker 1>test is less definitive for cetaceans and for primates, since

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<v Speaker 1>primates can touch the mark or the mirror, while cetaceans

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<v Speaker 1>can only twist and turn to view it. Skeptics suggest

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<v Speaker 1>behaviors interpreted as self awareness might just be social responses

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<v Speaker 1>to another individual. Supporters counter that the behaviors are distinctly

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<v Speaker 1>different from normal social responses. In nineteen ninety five, researchers

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<v Speaker 1>use television to test dolphin self awareness, showing dolphins real

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<v Speaker 1>time video of themselves, video of another dolphin, and recorded footage.

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<v Speaker 1>They concluded the evidence suggested self awareness rather than social behavior.

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<v Speaker 1>Since then, dolphins have passed the mirror test, though some

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<v Speaker 1>researchers remain unconvinced. Dolphins are highly social, often living in

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<v Speaker 1>pods of up to a dozen individuals. Those size and

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<v Speaker 1>structure vary widely by species and location. In areas with

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<v Speaker 1>abundant food, pods can merge temporarily into superpods that may

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<v Speaker 1>exceed a thousand dolphins. Pod membership is fluid. Individuals move

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<v Speaker 1>between groups. They form strong social bonds and will stay

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<v Speaker 1>with injured or ill members, bringing them to the surface

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<v Speaker 1>to breeze if needed. This altruism isn't limited to their

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<v Speaker 1>own species. A dolphin named Mocho and New Zealand was

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<v Speaker 1>observed guiding a stranded pygmy sperm whale and her calf

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<v Speaker 1>out of shallow water. Dolphins have also been seen protecting

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<v Speaker 1>human swimmers from sharks, either by swimming in circles around

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<v Speaker 1>them or charging the sharks. Communication happens through clicks, whistle

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<v Speaker 1>like sounds, and other vocalizations. Nonverbal communication includes touch and posturing.

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<v Speaker 1>Dolphins display culture, something long thought unique to humans and

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<v Speaker 1>perhaps other primates. In two thousand five, researchers in Australia

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<v Speaker 1>found into Pacific bottle nosed dolphins teaching their young to

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<v Speaker 1>use tools. They cover their snouts with sponges to protect

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<v Speaker 1>them ale foraging. This knowledge is mostly passed from mothers

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<v Speaker 1>to daughters, unlike in primates, where it's generally shared with

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<v Speaker 1>both sexes. The sponge use is a learned behavior. Dolphins

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<v Speaker 1>generally sleep with only one brain hemisphere and slow wave

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<v Speaker 1>sleep at a time, maintaining enough consciousness to breathe and

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<v Speaker 1>watch for threats. Earlier sleep stages can occur simultaneously in

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<v Speaker 1>both hemispheres. In capacity, dolphins sometimes enter a fully asleep

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<v Speaker 1>state with both eyes closed and no response to mild stimuli.

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<v Speaker 1>Respiration becomes automatic. A tail kick preflex keeps the blowhole

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<v Speaker 1>above water if necessary. Whether wild dolphins reach this state

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<v Speaker 1>is unknown. The Indus river dolphin has a different sleep method.

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<v Speaker 1>Living in water with strong currents and debris, it must

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<v Speaker 1>swim continuously to avoid injury, so it leaps in very

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<v Speaker 1>short bursts forward to sixty seconds at a time. Bottle

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<v Speaker 1>nosed dolphins have signature whistles, unique sounds that function like names.

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<v Speaker 1>These whistles identify individuals and are used to communicate over distance.

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<v Speaker 1>A dolphin develops its signature whistle during its first year

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<v Speaker 1>and maintains it for life. The development involves vocal production learning,

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<v Speaker 1>influenced by interactions with other dolphins. Dolphins can address one

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<v Speaker 1>another by mimicking a specific whistle. Male bottlenose whistles tend

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<v Speaker 1>to resemble their mothers. Female whistles are more distinctive. Bottlenose

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<v Speaker 1>dolphins have strong memories for these whistles. They can recognize

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<v Speaker 1>the signature whistle of an individual they haven't encountered in

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<v Speaker 1>over twenty years. Research on signature whistles and other species

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<v Speaker 1>is limited and as yielded mixed results. Because dolphins travel

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<v Speaker 1>in groups, communication is essential. Signal making occurs when similar

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<v Speaker 1>sounds interfere with the original acoustic signal, and larger groups,

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<v Speaker 1>individual whistles are less prominent. Dolphins travel in pods that

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<v Speaker 1>range from a few individuals to many. Though they don't

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<v Speaker 1>necessarily swim close to each other, they stay within the

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<v Speaker 1>same general area. Higher whistle rates help prevent losing pod

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<v Speaker 1>members when the group is spread out. Dolphins frequently leap

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<v Speaker 1>above the water for various reasons. When traveling. Jumping saves

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<v Speaker 1>energy less friction in the air. This is called porpoising.

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<v Speaker 1>Other reasons include orientation, social displays, nonverbal communication, entertainment, and

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<v Speaker 1>dislodging parasites. In the Port River north of Adelaide, several

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<v Speaker 1>Indo Pacific bottle nosed dolphins have been seen tailwalking, a

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<v Speaker 1>highly unusual behavior in the wild. This involves forcing most

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<v Speaker 1>of the body vertically out of the water and may

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<v Speaker 1>containing the position of vigorously pumping the tail, mimicking a

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<v Speaker 1>standing posture, and moving backward along the water. The behavior

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<v Speaker 1>started in nineteen eighty eight when a female named Billy

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<v Speaker 1>was rescued after becoming trapped in a polluted marina. She

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<v Speaker 1>spent two weeks recuperating with captive dolphins at a marine park,

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<v Speaker 1>where she observed them tailwalking. After being returned to the

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<v Speaker 1>Port River, she continued performing the behavior. Another dolphin wave

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<v Speaker 1>copied her Wave. A very active tailwalker, passed the skill

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<v Speaker 1>to her daughters, Ripple and Pilula. After Billy's early passing,

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<v Speaker 1>Wave increased her tailwalking, and other dolphins in the group

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<v Speaker 1>began performing it. By twenty eleven, up to twelve dolphins

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<v Speaker 1>had been observed tailwalking, though only females appeared to learned.

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<v Speaker 1>In October twenty twenty one, a dolphin was observed tailwalking

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<v Speaker 1>for hours. Scientists find the spread of this behavior through

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<v Speaker 1>up to two generations surprising, as it brings no apparent

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<v Speaker 1>advantage and is very energy consuming. Dolphins can tolerate and

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<v Speaker 1>recover from extreme injuries, though the exact mechanisms aren't known.

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<v Speaker 1>Even large wounds restore in a way that preserves body

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<v Speaker 1>shape and infection seems rare. A study published in Marine

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<v Speaker 1>Mammals Science suggests that at least some dolphins serve live

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<v Speaker 1>shark encounters using sophisticated maneuvers and cooperative tactics.