Hawaii's Spinner Dolphin(referenced from Kenneth S. Norris's Dolphin Days and Peter G. H. Evan's The Natural History of Whales and Dolphins)
What: Stenella Longisrostris the Latin name meaning long-snouted Spinner dolphin. The Hawaiian Spinner is considered one of 4 species of Spinner dolphins that live around the Hawaiian Islands.
What do Spinners look like? The slim spinner dolphin averages between 5-7 feet and its weight ranges between 110-160 pounds. There are three parts that make up the color pattern of the spinner; a dark back, pearl-gray side panels, and pure white belly. Their long, slim, blackish beaks are lined with 180 or more delicate interlocking conical teeth.
Where: Spinner dolphins can always be found in dolphin schools ranging from four to over 250 individuals in shore. The "school" is where dolphins give birth, raise and instruct their young, find and catch food, sleep; and schools of dolphins never stop moving, even during rest.
What is echolocation? Echolocation is how dolphins send and receive back as echoes. The form of echoes, including their loudness, can inform a dolphin of the size, shape and surface characteristics and movement of the object. The time lapse between emitting the signal and receiving the echo indicates how far away an object is.
So what, if dolphins echolocate? Because of echolocation, dolphins are able to search for, chase and catch fast swimming prey in total darkness. In captivity, a blindfolded dolphin can not only swim round a pool without ever hitting the walls but also can distinguish, for example, between balls of slightly different sizes or between, for example, between balls of slightly different sizes or between a hollow and a solid ball of the same size at 400 feet away. If you swim with a wild population of spinner's they know how much you weigh, if you're male or female, and if you're pregnant.
Why do Spinner dolphins spin? The dolphins who spin are letting the rest of the dolphin school know exactly where they are and in turn, serve as a local "geographical markers" and in group, mark out the dimensions of the school. Before spinning, a dolphin will produce a barking like sound well below the surface of the water thus, informing other dolphins when and where a spin is about to take place. With a listening dolphin's attention focused in the proper direction by the barks, the re-entry slap confirms that it was indeed a spin, and the bubble plume makes an excellent echolocation target, providing range and bearing for an echo locating school member.
How can you tell the difference between male and female spinner dolphins? Male spinners have deep muscular tails and are usually larger than the females. Males also have a peculiar ventral hump of tissue that looks like a radar dome, set just behind the anus. The curious post anal hump, marks the sex, and to a degree the age of the spinner dolphins that bears it. Big, old males have the largest humps.
What do they eat? Spinners eat a lot of very small food items: two-inch, bioluminescent lantern fish, deep-sea shrimp, and thumb-sized squids. Some of these squids never venture closer than 500 feet to the surface of the water. Spinners can dive to almost 1000 feet hunting for food.
Where and when do they have their babies? On average, newborn dolphins are most abundant in the late spring and summer, pregnancy lasts about 10.5 months and the babies are born within the school of dolphins. It is speculated that sexual behavior in these dolphins might be cued chemically probably by taste during mating season (late spring and summer). Females cycle through very brief peaks of sexual readiness (females who just ovulated), lasting just days. The male hormone patterns are quite different and they are sexually active throughout much of the mating season.
Can dolphins have twins? Yes, they can have twins but less than 1% have twins. Other adult females within the dolphin school will take care and feed the baby.
How long do the Spinner dolphins live? On the average, 20 years of age.
Loaded Gun Theory: Dolphins using their sonar to create "bullets" made out of sound. They direct their sound "bullets" in unison, at their prey. They can actually kill their prey with sound. Thus large school of dolphins, sometimes numbering in the thousands, in the open ocean represents a powerful hunting group. This theory has been documented with captive bottle nose dolphins using nose dolphins using their sound to kill anchovy.
Which whale or dolphins dives the deepest? The sperm whale which has been spotted off shore of shore of the Hawaiian Islands will dive over 12,000 feet (over 2 miles) for squid and can hold its breath up to 3 hours.
Dolphins are awake 24 hours a day. Dolphins alternate their brain halves when they sleep. In other words only one side of their brain is sleeping while the other side is wide awake. Then they alternate brain halves. Dolphins are conscious breathers and have to "remember" to come to the surface of the water to breath and they need to be able to respond to any danger signals i.e. sharks.
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