Unlike most dolphins, Risso's has no prominent beak — just a blunt, rounded snout with a distinctive vertical crease down the forehead. Adults become increasingly white with age as scar tissue accumulates from encounters with squid and other Risso's Dolphins.
Risso's Dolphins rely heavily on echolocation for squid hunting in deep, dark water. Their echolocation clicks are particularly adapted for squid detection.
Risso's Dolphins produce clicks and burst-pulse sounds for echolocation and social communication.
Deep divers, regularly reaching depths of 1,000–1,600 feet in pursuit of squid. Dive times can exceed 30 minutes. They locate individual squid by echolocation.
Gestation
13–14 months. Females give birth every 2–3 years.
Birth
Calves are approximately 47 inches long and weigh around 44 lbs at birth. Born uniformly dark grey — very different from adults.
Calves
Calves nurse for 12–18 months. Calves gradually develop the adult scarred pattern through their first 5–10 years.
Females reach sexual maturity at 8–10 years; males at 10–12 years.
Typically found in groups of 10–50. Larger aggregations of several hundred can occur when food is concentrated.
Risso's Dolphins are capable of impressive breaches and tail slaps. Deep dives of 30+ minutes are routine.
The white scar-covered appearance of old Risso's Dolphins is unique among cetaceans. The more scars, the older and more experienced the animal.
30–40 years. Threats include deep-water longline bycatch, noise pollution from military sonar, marine debris ingestion, and organochlorine contamination.
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