Rough-toothed dolphins are named after their peculiar teeth. Each tooth is ridged or wrinkled and has scratch marks on the surface.
Rough-toothed dolphins have a distinctive appearance; they look like primitive dolphins; almost reptilian.
Other names: slopehead; steno
IUCN conservation status: Least Concern
What do rough-toothed dolphins look like?
Rough-toothed dolphins are unusual looking dolphins as their overall appearance is quite primitive, a bit like a prehistoric dolphin. They have a small head and are the only long-beaked dolphins without a noticeable crease between their beak and forehead. They have a long, white-coloured beak that smoothly blends into the sloping forehead. The body is black to dark grey on the back and light grey and white on the belly, sometimes tinged with pink. The body is dotted with white, uneven splotches and white, circular scars left by cookiecutter shark bites.
The flippers are fairly long and large and the dorsal fin is tall and only slightly ‘hooked’ or curved.
What’s life like for a rough-toothed dolphin?
Rough-toothed dolphins are generally found in tight-knit groups of 10 to 20 with seemingly strong social structure. Rough-toothed dolphins have large brains and are believed to be one of the most intelligent dolphin species. Groups as large as 140 to 160 have been seen near Hawaii and in the Mediterranean. They are highly sociable dolphins and frequently mix and travel with other oceanic dolphins including bottlenose dolphins, pantropical spotted dolphins, Fraser’s dolphins, spinner dolphins and short-finned pilot whales.
Rough-toothed dolphins do not swim as quickly as other types of dolphins. They swim at slow to moderate speeds and skim along the surface, keeping very close together in tight formation and making a distinctive splash. Most of their daytime activities appear to be related to travelling and hunting. Their movement patterns are dictated by prey availability. Rough-toothed dolphins are not as agile as other dolphins but they do leap and ride bow waves.
They are able to dive underwater for at least 15 minutes at a time.
What do rough-toothed dolphins eat?
Like other dolphins, rough-toothed dolphins have a flexible diet, but seem to particularly like eating large fish such as mahi-mahi (or dorado) that live at the surface. They have also been known to eat houndfish, smelt, squids and octopuses.
Where do rough-toothed dolphins live?
Rough-toothed dolphins live in deep oceanic, tropical and warm-temperate waters in the Atlantic, Pacific and Indian Oceans (all the world’s major oceans). They prefer areas with lots of available prey and are usually found offshore usually beyond the continental shelf; but in some areas they live in shallow coastal waters such as Brazil and Honduras.
Mystery of the white dolphin
An all-white rough-toothed dolphin was photographed off Gabon, West Africa, but researchers were unable to determine whether this white colouration was due to albinism or simply lack of pigmentation. Piebald rough-toothed dolphins have also occasionally been seen; they have larger than normal patches of white on their black skin.
Rough-toothed dolphins need your help
The main threats...
- Entanglement in nets - The main threat to rough-toothed dolphins is injury and death due to entanglement in fishing nets and equipment such as gillnets and long-lines. They are known to take bait from fishermen’s hooks in Hawaii and some become entangled and die.
- Hunting - Although not the main target species, rough-toothed dolphins have been killed in direct fisheries in Taiwan, Japan, Sri Lanka, Indonesia, Papua New Guinea, the Solomon Islands, West Africa, and the Caribbean Sea.
- Noise pollution - Underwater noise pollution interrupts the normal behaviour of rough-toothed dolphins, which rely on sound to communicate and echolocate. Noise disturbance from boats and ships, as well as industrial and military activities, impacts rough-toothed dolphins’ ability to successfully hunt, communicate and navigate.
- Captivity - Rough-toothed dolphins have been held in captivity in Hawaii for example and this is unusual as oceanic dolphins do not generally survive in captivity.