Risso’s Dolphin

Grampus griseus

Renowned for their heavily scarred appearance and significant size.

Risso’s dolphin, named after Antoine Risso, a naturalist whose work led to the formal description of the species by Georges Cuvier, is a distinctive member of the Delphinidae family. This species stands out due to its robust body, especially in front of the dorsal fin, and a bulbous, squarish head with an indistinct beak, traits that differentiate it from other cetaceans. The dolphin’s skin, ranging from dark to pale grey and often covered in white scratches and blotches, tells a story of its life beneath the waves, including interactions with both conspecifics and prey such as squid, evident from the scars and markings. Its tall, erect dorsal fin, one of the tallest in proportion to body length among cetaceans, and long, pointed flippers add to its unique silhouette in the marine landscape.

Risso’s dolphins exhibit a fascinating array of behaviors and physical characteristics that set them apart in the oceanic realm. Their coloration and the extent of scarring become more pronounced with age, especially in males, leading to a predominantly white appearance in older individuals. This coloration, alongside the distinct vertical crease on the melon, contributes to their unique identification. Their presence across various marine environments, from tropical to cool temperate waters, highlights their adaptability and the broad range of habitats they occupy.

Quick facts

Length

Male: 3,8m

Female: 3,8m

Calf: 1,5m

Weight

Adults: 500 kg

Calves: 30 kg

Habits

Dive Time

<10min

Dive Depth

<460m

Reproduction

40-50 years

Life Span:

13-14mth

Gestation period:

Physical characteristics

Group Structure

Risso’s dolphins form groups typically numbering 5–30, but can aggregate into much larger gatherings, sometimes reaching up to 4,000, particularly off California. These groups exhibit a stratified structure, with clusters formed based on age and sex classes. Males form highly stable social units, while females create stable nurseries during calving seasons. Young dolphins often stay near their natal groups for years after weaning, eventually forming bachelor pods around the ages of 6–8.

Dive sequence

@Georgina Cabayol

Behavior

Socializing +

Risso’s dolphins engage in various aerial activities such as breaching, spyhopping, and lobtailing as part of their socializing behavior. These activities likely serve communication and social bonding purposes within their groups.

Resting +

During the daytime, Risso’s dolphins are observed resting, along with engaging in social activities and traveling. Resting behaviors may include reduced activity levels and slower movements, allowing the dolphins to conserve energy.

Foraging & Diet +

Risso’s dolphins primarily feed on deepwater squid and octopuses, with occasional consumption of cuttlefish and krill. They typically forage during late afternoon and night, taking advantage of nocturnal migrations of their prey. Cooperative feeding behaviors are observed, likely aiding in capturing elusive prey in the deep ocean environment.

Predators

Risso’s dolphins face predation threats from sharks and killer whales, as indicated by wounds from attacks observed on their bodies. These predators may target Risso’s dolphins opportunistically, especially during vulnerable times such as foraging or resting, posing a risk to individual dolphins and potentially impacting population dynamics.

https://uk.whales.org/whales-dolphins/species-guide/rissos-dolphin/

Distribution & Movements

This species has a wide distribution, found from tropical to cool temperate waters between approximately 64°N and 46°S. They prefer mid-temperate waters, continental shelves, and slopes, showing seasonal movements in some regions. Their distribution is also influenced by oceanographic conditions and prey availability.

Reproduction & Life History

Sexual maturity

8-12 years
Females 8–10 years, males 10–12 years

Gestation period

13–14 months

Number of calves

Typically one calf

Suckling period

12-24 months
Males about 12 months, females about 20–24 months

Nursing

Calves are nursed and weaned at different intervals based on gender

Lifespan

Estimated at 40–50 years

Mating strategy

Promiscuous
Likely promiscuous with sperm competition, extensive scarring as a possible indicator of ‘quality’ among individuals.

Species in the Azores

Specimen that you can see in Azores sea

Blue Whale

Balaenoptera musculus

Blue whales are the largest animals in the world and can easily be detected from a great distance.

Blue Whale

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Sperm Whale

Physeter macrocephalus

Sperm whales hold the title of largest predator on Earth eating mostly giant squids from the deep oceans.

Sperm Whale

Physeter macrocephalus

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Bryde’s Whale

Balaenoptera edeni

The Bryde's whale live in the tropical waters, are agile filter feeders and love to perform acrobatic displays.

Bryde’s Whale

Balaenoptera edeni

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Fin Whale

Balaenoptera physalus

The second-largest whales, swift and streamlined ocean roamers.

Fin Whale

Balaenoptera physalus

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Minke Whale

Balaenoptera acutorostrata

Agile mid-sized baleen whales, known for their elusive nature.

Minke Whale

Balaenoptera acutorostrata

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Nothern Bottlenose Whale

Hyperoodon ampullatus

Nothern Bottlenose Whale

Hyperoodon ampullatus

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Pilot Whale (Long & Short-finned)

Globicephala melas | Globicephala macrorhynchus

Highly social, intelligent & deep divers.

Pilot Whale (Long & Short-finned)

Globicephala melas | Globicephala macrorhynchus

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Blainville’s Beaked Whale

Mesoplodon densirostris

Elusive deep-divers known for their unique foraging behavior.

Blainville’s Beaked Whale

Mesoplodon densirostris

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Sei Whale

Balaenoptera borealis

Third-largest whale species on Earth, fast swimmers and deep-divers.

Sei Whale

Balaenoptera borealis

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Cuvier’s Beaked Whale

Ziphius cavirostris

Noted for extraordinary deep-diving, setting mammalian records in depth and duration

Cuvier’s Beaked Whale

Ziphius cavirostris

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Humpback Whale

Megaptera novaeangliae

Melodic giants with acrobatic displays, known for their haunting songs and intricate social behaviors. Know more!

Humpback Whale

Megaptera novaeangliae

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Atlantic Spotted Dolphin

Stenella Frontalis

Highly social, with distinct spots and a wide range of complex behaviors and vocalizations.

Atlantic Spotted Dolphin

Stenella Frontalis

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Striped Dolphin

Stenella coeruleoalba

Notable for their striking body patterns and acrobatic prowess.

Striped Dolphin

Stenella coeruleoalba

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Bottlenose Dolphin

Tursiops truncatus

Bottlenose Dolphins are highly intelligent and social creatures, famous for their playful behavior and remarkable cognitive abilities.

Bottlenose Dolphin

Tursiops truncatus

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Orca (Killer Whale)

Orcinus orca

Orcas are the apex predators of the marine world, known for their distinctive black and white coloring and complex social structures.

Orca (Killer Whale)

Orcinus orca

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Common Dolphin

Delphinus delphis

Large groups of common dolphins, whipping the ocean's surface into a froth, are a familiar and thrilling sight in many parts of the world.

Common Dolphin

Delphinus delphis

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False Killer Whale

Pseudorca crassidens

Despite its name, the false killer whale belongs taxonomically to the dolphin family and it often behaves more like one of its energetic and sprightly smaller relatives.

False Killer Whale

Pseudorca crassidens

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Sowerby’s Beaked Whale

Mesoplodon bidens

Sowerby’s Beaked Whales are elusive denizens of the North Atlantic, recognized by their slender beaks and distinctive forehead bulges.

Sowerby’s Beaked Whale

Mesoplodon bidens

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Risso’s Dolphin

Grampus griseus

Risso's dolphin is renowned for its heavily scarred appearance and significant size among species referred to as dolphins.

Risso’s Dolphin

Grampus griseus

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Dragoeiro

Dracaena draco

Dragoeiro

Dracaena draco

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Atlantic Spotted Dolphin

Stenella Frontalis

Highly social, with distinct spots and a wide range of complex behaviors and vocalizations.

Atlantic Spotted Dolphin

Stenella Frontalis

View profile

Blainville’s Beaked Whale

Mesoplodon densirostris

Elusive deep-divers known for their unique foraging behavior.

Blainville’s Beaked Whale

Mesoplodon densirostris

View profile

Bottlenose Dolphin

Tursiops truncatus

Bottlenose Dolphins are highly intelligent and social creatures, famous for their playful behavior and remarkable cognitive abilities.

Bottlenose Dolphin

Tursiops truncatus

View profile

Common Dolphin

Delphinus delphis

Large groups of common dolphins, whipping the ocean's surface into a froth, are a familiar and thrilling sight in many parts of the world.

Common Dolphin

Delphinus delphis

View profile

Cuvier’s Beaked Whale

Ziphius cavirostris

Noted for extraordinary deep-diving, setting mammalian records in depth and duration

Cuvier’s Beaked Whale

Ziphius cavirostris

View profile

False Killer Whale

Pseudorca crassidens

Despite its name, the false killer whale belongs taxonomically to the dolphin family and it often behaves more like one of its energetic and sprightly smaller relatives.

False Killer Whale

Pseudorca crassidens

View profile

Nothern Bottlenose Whale

Hyperoodon ampullatus

Nothern Bottlenose Whale

Hyperoodon ampullatus

View profile

Orca (Killer Whale)

Orcinus orca

Orcas are the apex predators of the marine world, known for their distinctive black and white coloring and complex social structures.

Orca (Killer Whale)

Orcinus orca

View profile

Pilot Whale (Long & Short-finned)

Globicephala melas | Globicephala macrorhynchus

Highly social, intelligent & deep divers.

Pilot Whale (Long & Short-finned)

Globicephala melas | Globicephala macrorhynchus

View profile

Risso’s Dolphin

Grampus griseus

Risso's dolphin is renowned for its heavily scarred appearance and significant size among species referred to as dolphins.

Risso’s Dolphin

Grampus griseus

View profile

Blue Whale

Balaenoptera musculus

Blue whales are the largest animals in the world and can easily be detected from a great distance.

Blue Whale

Balaenoptera musculus

View profile

Bryde’s Whale

Balaenoptera edeni

The Bryde's whale live in the tropical waters, are agile filter feeders and love to perform acrobatic displays.

Bryde’s Whale

Balaenoptera edeni

View profile

Fin Whale

Balaenoptera physalus

The second-largest whales, swift and streamlined ocean roamers.

Fin Whale

Balaenoptera physalus

View profile

Humpback Whale

Megaptera novaeangliae

Melodic giants with acrobatic displays, known for their haunting songs and intricate social behaviors. Know more!

Humpback Whale

Megaptera novaeangliae

View profile

Minke Whale

Balaenoptera acutorostrata

Agile mid-sized baleen whales, known for their elusive nature.

Minke Whale

Balaenoptera acutorostrata

View profile

Sei Whale

Balaenoptera borealis

Third-largest whale species on Earth, fast swimmers and deep-divers.

Sei Whale

Balaenoptera borealis

View profile

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Risso’s Dolphin

Grampus griseus

Renowned for their heavily scarred appearance and significant size.

Quick facts

Length

Weight

Habits

Reproduction

Reproduction

IUCN RED LIST STATUS: Least Concern <img class="graphics-design-i" src="/wp-content/uploads/2024/01/tooltip-more-info-futurismo.svg"> Common and widespread, low vulnerability.

Physical characteristics

Group Structure

Dive sequence

Behavior

Predators

Distribution & Movements

Reproduction & Life History

Sexual maturity

Gestation period

Number of calves

Suckling period

Nursing

Lifespan

Mating strategy

Species in the Azores

Sighting frequency

Sighting frequency

BY SPECIES

Sighting frequency

BY SPECIES

Species

Departure Points

Dates

Related Scientific Articles

Sardà, C. et al (2011): AzoresPhotoID: First Results from an Open-Access Photo-Identification Catalog

Martins, R. et al (2019): Residency Patterns of Risso’s Dolphins off São Miguel and Inter-Island Matches with Pico Island

Martins, R. et al (2018): Discovering a Resident Family of Risso’s Dolphins off São Miguel

Sousa, A. et al (2021): Climate change vulnerability of cetaceans in Macaronesia

Martins, R. (2021): Developing a photo-ID app to identify Risso’s dolphins off São Miguel, Azores

González, L. (2018): Spatio-temporal distribution of the order Cetacea in the Azores: relationship between biotic and abiotic variables

Specimen that you can see in Azores sea

Blue Whale

Balaenoptera musculus

Blue Whale

Balaenoptera musculus

Sperm Whale

Physeter macrocephalus

Sperm Whale

Physeter macrocephalus

Bryde’s Whale

Balaenoptera edeni

Bryde’s Whale

Balaenoptera edeni

Fin Whale

Balaenoptera physalus

Fin Whale

Balaenoptera physalus

Minke Whale

Balaenoptera acutorostrata

Minke Whale

Balaenoptera acutorostrata

Nothern Bottlenose Whale

Hyperoodon ampullatus

Nothern Bottlenose Whale

Hyperoodon ampullatus

Pilot Whale (Long & Short-finned)

Globicephala melas | Globicephala macrorhynchus

Pilot Whale (Long & Short-finned)

Globicephala melas | Globicephala macrorhynchus

Blainville’s Beaked Whale

Mesoplodon densirostris

IUCN RED LIST STATUS: Least Concern

Common and widespread, low vulnerability.