The rough-toothed dolphin (Steno bredanensis) has a sloping head and long beak, and has been described as looking "reptilian" in appearance. Despite having a fairly large population size, these dolphins, which prefer deep waters in the open ocean and around oceanic islands, are not very well-studied.
Rough-toothed dolphins are relatively small, reaching a maximum length of 8.5 feet and weight of 350 pounds. Males are longer than females.They have a stocky body, long beak (rostrum), large dorsal fin and long flippers. Their coloration ranges from dark gray to black on the back to medium-gray sides and a white underside. They have a dark "cape" on their back that starts at the top of the head and runs behind the dorsal fin. They may also have which spots or patches, which are scars from cookie-cutter sharks.
These dolphins have ridges and wrinkles on the enamel of their teeth, which earned them their name. They have 20-27 teeth on each side of their upper and lower jaw.
- Kingdom: Animalia
- Class: Mammalia
- Order: Cetacea
- Suborder: Odontoceti
- Family: Delphinidae
- Genus: Steno
- Species: bredanensis
Habitat and Distribution
Rough-toothed dolphins often travel in groups of 10-20 animals, although they may gather in groups of several hundred individuals. They also associate with other species, including pilot whales, bottlenose dolphins, spinner dolphins, and pantropical spotted dolphins. They are sometimes slow swimmers, and often swim along the water surface with their chin and head above the water.
Rough-toothed dolphins are found in deep, warm temperate and tropical waters around the globe (click here for a range map). In the U.S., they are found primarily off Hawaii and in the Gulf of Mexico. They frequent the open ocean and areas around oceanic islands.
Diet and Feeding
Rough-toothed dolphins are thought to feed primarily on squid and fish, and are capable of diving deeply when foraging for prey.
Rough-toothed dolphins are sexually mature at 10-14 years of age. As with other cetacean species, reproduction is sexual, with internal fertilization. The length of gestation is unknown. Calves are about 3-4 feet long at birth.
Their maximum lifespan is thought to be about 32 years.
In 2012, the IUCN stated that rough-toothed dolphins are widespread and abundant, with current population estimates around 150,000, although research should be encouraged to learn more about the species. They are listed as "Least Concern" on the IUCN Red List.
Threats to these dolphins include drive fisheries for their meat, in Japan, Sri Lanka, Indonesia, the Solomon Islands and Papua New Guinea, although relatively few dolphins are taken. They also may be captured as bycatch in fishing gear. They are displayed in marine parks/aquariums in some areas.
References and Further Information
- ARKive. Rough-toothed Dolphin. Accessed November 18, 2013.
- Baird, R., et. al. 2008. Site ﬁdelity and association patterns in a deep-water dolphin: Rough-toothed dolphins (Steno bredanensis) in the Hawaiian Archipelago. Marine Mammal Science, 24(3): 535–553 (July 2008). Accessed online November 18, 2013.
- Cascadia Research. Rough-toothed Dolphins in Hawai'i (Note: there are great images on this page!). Accessed November 18, 2013.
- Department of the Environment. 2013. Steno bredanensis in Species Profile and Threats Database, Department of the Environment, Canberra. Available from: http://www.environment.gov.au/sprat. Accessed November 18, 2013.
- Hammond, P.S., Bearzi, G., Bjørge, A., Forney, K.A., Karkzmarski, L., Kasuya, T., Perrin, W.F., Scott, M.D., Wang, J.Y. , Wells, R.S. & Wilson, B. 2012. Steno bredanensis. In: IUCN 2013. IUCN Red List of Threatened Species. Version 2013.1. Accessed November 18, 2013.
- Museum Victoria. Rough-toothed Dolphin (Video, prior to a necropsy). Accessed November 18, 2013.
- NOAA Fisheries. Rough-toothed Dolphin (Steno bredanensis). 2012. Accessed November 18, 2013.