dolphin pods rely on socialites to keep them together. without these individuals, the cohesion of the dolphin group may fall apart. this may mean that capturing wild dolphins for marine parks could have a serious impact on their companions left behind.
spinner dolphins are aptly named for their above-water actions. they can leap into the air and make as many as seven complete spins before diving back into the ocean again. in hawaii, the spotted dolphins can leap higher (we've had them jump high enough to be at eye level to us in a vessel's tuna tower!) than a spinner, but except for the clymene dolphin, no other dolphins spin (naturally anyhow).
the spinner dolphins usually perform a series of spins, each spin tending to be made with less energy, finally finishing up with an emphatic side slap. the power of the spin comes from the tremendous acceleration under the water and the torque of the tail just as the dolphin breaks the surface. the aftermath of the spin the sound of the slap, the splash on the surface, and the dense bubble cloud underwater, which even distant dolphins can pick up through their echolocation may be the real purpose of the spin.
spinner dolphins maximize the effect of this splash by twisting around to land in a belly-flop, or back-flop. spins are most frequently performed while the school is spread out across the water. a spinning dolphin may be signaling to the others: "here i am here is where i am going..." the effect of many dolphins spinning and leaping at once, defines what scientists call the envelope of the school that is, its size, direction, and speed of travel.
why do spinner dolphin's spin?
from our underwater observations, the spin seems to be an emotional "exclamation point" to whatever action happened just before the spin. it can accent any emotion from "i'm really happy that just happened" to a stern "listen to me now!" it may also be a teaching (or learning) demonstration, or simply, "i am a spinner, therefore i spin." interestingly, the textbook reason is to "rid themselves of parasites." we also find this to be true. watch this little spinner dolphin calf spin (four rotations!) to rid himself of the remora skimming around his shoulder region. (the video works in windows media player.)
spinning may also serve as a courtship display, or to eject water from the upper respiratory tract, reset organs of balance, help mix fluid in the gut and venous reservoirs, or simply be for fun. it might also be important to spinner dolphins' thermal budget since core and subcutaneous temperature are highest when the dolphins are spinning.
this aerial behavior is probably the most energetic. the head-over-tail leap is a spectacular series of mid-air somersaults.
head slaps send acoustical messages that often are intended to get the attention of other dolphins. head slaps in some cases are used to indicate to the pod the direction of travel desired by the slapper.
tail or peduncle (tail stock) slaps
these are often seen before a change in the pods behavior. most often, immediately after we see this behavior, the pod will change its traveling direction. tail slap video and how it looks from underwater. the dolphin is excited about his "play toy"! the spinners use tail slaps as acoustic signals giving cues about danger, or a signal to dive.
these are either the last behavior seen before going into (or entering out of) a deep rest mode, or when they seem to have interest in us (taking a look!).
these behaviors, although still classified as aerial behaviors, are the least energy-taxing.
dives with the tail (flukes) raised in the air seem to signal deep dives. this a borderline aerial behavior as it still happens above the water line, but is not very active. we rarely see spinner dolphins do this (perhaps because they are in shallow water) but bottlenose do this all the time.
spinners often will make a "play-toy" of an object in their environment. in our area, the tradewinds blow lightweight plastic grocery bags into the ocean. the dolphins drape these over their fins and pass them back and forth. the same behavior can be seen with seaweed and other objects.
newborn calves can be seen swimming near their mothers head for about a week before they swim nearer to her dorsal fin. this is termed as echelon swimming. dolphins carry their young inside their womb and gestation is about 10 months for a spinner. the baby emerges tail first, and will suckle from its mother for up to 2 years. other details seen in a newborn are fetal folds wrinkles along their sides where they were curled up in the womb, and floppy dorsal fins. the dorsal fin, made of cartilage, takes a few days after birth to become hard and rigid. the softness allows it to fold over against the calf's back during birth. much more pleasant for mom!
researchers have long speculated as to how dolphin calves are able to keep up with their fast-swimming mothers. one favored theory has been that they employ "drafting," defined as "the transfer of forces between individuals without actual physical contact between them." kinda like when you sucked into a passing truck on the freeway, a free ride for awhile.
dolphins breathe through their blowhole located at the top of their head. oceanic dolphins have evolved a method of breathing without surfacing from the water. they blow a bubble when near the water surface and then quickly draw breath in when the bubble forms a bridge between the blowhole and the air, through the water. a dolphin may empty and refill its lungs in less than a fifth of second. as the dolphin breathes the air leaves the blowhole at speeds of over 100 miles per hour. to sleep, a dolphin "shuts down" only half of its brain, as its breathing is under voluntary control.
this helps to explain...
how do dolphins sleep?
in order to live most of their lives underwater, dolphins are conscious breathers: they think about when to breathe (probably as much as we think about walking). therefore, in order to breathe, they have to be conscious. so what if they don't wake up in time? dolphins cope with this by putting one half of the brain to sleep at a time (literally sleeping with one eye open). in this way, the animal is never completely unconscious, but it still gets the rest it needs. the two hemispheres "take turns" cycling up and down for a few hours. this also keeps the dolphins from losing body heat and getting too cold (taking up energy to keep warm). think how you get cold when you sleep, even when the temperature hasn't changed.
spinner dolphins' pectoral flippers are used to steer them through the water, they also use them to stroke one another, increasing and affirming social bonds. dolphin "friends" may swim along, touching flippers and stroking each other. dolphins that appear to be closely bonded may swim in synchrony, twisting, turning and swimming in perfect harmony together.
vocalization and sonar (echolocation)
spinner dolphins can be very noisy under and above water, click here for underwater video and audio of spinner dolphins vocalizing and a signature whistle. echolocation enables dolphins to track objects in dim or dark water, in effect to "see" much further than their eyes alone will allow. their complex array of whistle sounds are the way that dolphins talk to one another. the spinners also identify themselves with sounds they make while trailing bubbles from their blowholes sounds called signature whistles.
the ability to determine which direction a sound is coming from underwater (directional hearing) is vital for dolphins and other toothed whales. they pinpoint their prey through echolocation, in which some of the click train sent out bounces off an object and returns to them in hologram form. dolphins then interpret this returning echo to determine the object's distance, shape and other characteristics.
expertly using the pressure wave off the bow, the dolphins get an effortless
exhilarating ride... surfing sideways and even upside-down in the