Rough-toothed dolphins leaping off the island of Hawai‘i. Photo by Robin Baird. Rough-toothed dolphins (Steno bredanensis) are the fifth-most frequently encountered species of toothed whale in our study, representing 10% of all odontocete sightings from 2000 through 2009. Rough-toothed dolphins are typically found in deeper parts of our study area, so off the island of Hawaii, where we spend more than half our time surveying in depths > 1,000 m, they are the third-most frequently encountered species.
Rough-toothed dolphin group. Photo by Greg Schorr. Although we occasionally find lone individual rough-toothed dolphins, we have documented one group of over 100 individuals (off of Ni‘ihau). The most frequently encountered group size is three individuals, although the median group size is seven. Individual rough-toothed dolphins can be identified both by the notches on the trailing edge of the dorsal fin, but also by pigmentation patterns visible in the photo above, that remain virtually unchanged for years.
Rough-toothed dolphin leaping. Photo by Robin Baird. The numerous scars on the belly of this individual are caused by cookie-cutter sharks.
A juvenile rough-toothed dolphin. Photo by Jessica Aschettino. The gently sloping rostrum, or beak, is characteristic of the species.
A rough-toothed dolphin leaping. Photo by Robin Baird. This individual has a number of small remoras on the back, and may be leaping in an attempt to dislodge them. Note the very large pectoral flippers, characteristic of this species. As well as photo-identifying individuals to examine movements and social organization, we are also collecting biopsy samples of this species for contribution to genetic studies of stock structure.
For more information on rough-toothed dolphins see the following publication:
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