What kinds of dolphins do we normally see off the coast of the Big Island?
Of the 33 to maybe 57 species of dolphins in the world (researchers don’t agree on the number), only 13 species are found off Hawaiian waters, and of those 13, just 4 are commonly seen here: Spinners, Spotted, Rough Tooth, and Bottlenose.
What’s the difference between dolphins, porpoises and whales?
All these animals are members of the order Cetacea, and the sub-order Odontocete, which means all of these animals are toothed whales. The word ”dolphin“ typically refers to animals who have pronounced beaks, falcate (curved like a boomerang) dorsal fins, and conical shape teeth. ”Porpoises“ are animals with a blunt face, spatula shaped teeth (i.e. flat - like your own front teeth) and triangular dorsal fins. ”Whales“ are just really big cetaceans. To confuse the subject even more, a lot of local people here refer to the mahi-mahi fish as a dolphin, and to the smaller toothed whales as porpoises. That’s why researchers prefer to use all these animals’ Latin names for identification.
So, what’s the Latin genus and species name for the Spinner Dolphin? And what’s the Hawaiian name?
The Latin name is Stenella longirostris. Stenella comes from a Greek word that means “narrow“ and longirostrus means “long snout“. Hawaiians call almost all dolphins ”Nai’a” - though the name ”Kiko“ is used for the Spotted Dolphins (”kiko“ means spot or dot).
How did these dolphins get the common name “Spinner” ?
Watch these dolphins for a few minutes, and it’s pretty obvious. Spinners are really active on the surface!
Why do they exert so much energy jumping out of the water?
Although it may look like it’s simply a lot of fun, researchers believe that spinning is part of a dolphin’s job. Spinners spin most often at night, when the pod is more spread out and active. Reentry also creates a huge bubble plume which may make it easier for other dolphins to echolocate. So spinning is a way to keep track of where everyone is in the dark. Another popular theory explaining spinning behavior is that dolphins often have hitchhikers on their bodies (a fish called a remora, and a shark called a ”cookie-cutter“ shark). Jumping out of the water and landing with a big splash can get rid of those animals pretty quickly!
Do dolphins play with each other?
It sure looks like they do! We’ve seen them pick up debris like leaves or discarded line in the ocean and pass it to each other, balancing it on their pectoral fins.
What are all those sounds that I hear the dolphins making, and why are they so noisy?
Every dolphin has his own distinct whistle and everyone in the pod recognizes whose it is (even calves recognize their Mom’s whistle soon after birth). They make these sounds by moving air around in their nasal sacs, and the chambers behind their melons (their big foreheads). They can use sound to keep track of each other, but they also use it to find prey (biosonar).
Tell me about the life cycle of a Spinner dolphin.
Ok. After about a 10 ½ month gestation period a Spinner is born tail first. We believe his Mom will lift him to the surface for his first breath, but he’s immediately able to swim and suckle. At birth, he’s somewhere around 1 ½ feet to 2 ½ feet long. He’ll nurse on milk from his Mom that’s almost 40% fat (human milk contains about 4% fat). The calf isn’t weaned until he’s somewhere between 12 and 24 months, but he’ll stay in association with his Mom for longer (several years). If the calf is a female, she’ll reach sexual maturity around age 5-7, and if he’s male, he’ll reach sexual maturity around age 10. A fully grown Spinner is pretty small - males average 7 feet long and about 180 pounds and females are slightly smaller. Though a female will calve on average every 2-3 years (and almost always to a single baby - fewer than 1% were observed with twins), we have observed much more frequent mating behaviors. Both males and females mate socially (the female doesn’t have to be in estrus - in heat - for mating to occur) which is unusual in the animal kingdom. Spinners live an average of 20 years.
