Spinner Dolphin

Spinner dolphins were named for their unique behavior of leaping and spinning. These spins can involve more than four body revolutions.

Identification

Spinner dolphins are medium-sized dolphins with long, slender beaks. Coloration varies depending on where they live. They often have a striped appearance with a dark gray back, gray flanks and white underside. In some adult males, the dorsal fin looks as if has been stuck on backwards.

These animals may associate with other marine life, including humpback whales, spotted dolphins and yellowfin tuna.

Classification

There are 4 subspecies of spinner dolphin:

• Gray's spinner dolphin (Stenella longirostris longirostris)
• Eastern spinner dolphin (S. l. orientalis)
• Central American spinner dolphin (S.l. centroamericana)
• Dwarf spinner dolphin (S.l. roseiventris)

Habitat and Distribution

Spinner dolphins are found in warm tropical and subtropical waters in the Pacific, Atlantic and Indian Oceans.

Different spinner dolphin subspecies may prefer different habitats depending on where they live. In Hawaii, they live in shallow, sheltered bays, in the Eastern Tropical Pacific, they live on the high seas far from land and often associate with yellowfin tuna, birds and pantropical spotted dolphins. Dwarf spinner dolphins live in areas with shallow coral reefs, where they feed during the day on fish and invertebrates. Click here for a sighting map for spinner dolphins.

Feeding

Most spinner dolphins rest during the day and feed at night. Their preferred prey are fish and squid, which they find using echolocation. During echolocation, the dolphin emits high-frequency sound pulses from an organ (the melon) in its head. The sound waves bounce off objects around it and are received back into the dolphin's lower jaw. They are then transmitted to the inner ear and interpreted to determine the size, shape, location and distance of prey.

Reproduction

The spinner dolphin has a year-round breeding season After mating, the female's gestation period is about 10 to 11 months, after which a single calf about two and a half feet long is born. Calves nurse for one to two years.

The lifespan for spinner dolphins is estimated at about 20 to 25 years.

Conservation

The spinner dolphin is listed as "data deficient" on the IUCN Red List.

Spinner dolphins in the Eastern Tropical Pacific were caught by the thousands in purse seine nets targeting tuna, although their populations are slowly recovering due to restrictions placed on those fisheries.

Other threats include entanglement or bycatch in fishing gear, targeted hunts in the Caribbean, Sri Lanka, and the Philippines, and coastal development which affects the sheltered bays that these dolphins inhabit in some areas during the day.

Sources and Further Information

• American Cetacean Society. Spinner Dolphin: . Accessed April 30, 2012.Stenella longirostris (Short-Beaked) and Delphinus capensis (Long-Beaked)
• Culik, B. 2010. Odontocetes. The toothed whales: "Stenella longirostris". UNEP/CMS Secretariat, Bonn, Germany. Accessed April 30, 2012.
• Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K., Karczmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y., Wells, R.S. & Wilson, B. 2008. Stenella longirostris. IUCN 2011. IUCN Red List of Threatened Species. Version 2011.2. Accessed April 30, 2012.
• Nelson, B. 2011. Why Does This Dolphin Have Its Fin On Backwards?. Mother Nature Network, Accessed April 30, 2012.
• NOAA Fisheries: Office of Protected Resources. Spinner Dolphin (. Accessed April 30, 2012.Stenella longirostris)
• OBIS SEAMAP. Spinner Dolphin (. Accessed April 30, 2012.Stenella longirostris)
• Perrin, W. 2012. Stenella longirostris (Gray, 1828). In: Perrin, W.F. World Cetacea Database. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=137109 on April 30, 2012.
• The Mammals of Texas. Spinner Dolphin. Accessed April 30, 2012.