Sei Whale

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

Sei Whales, characterized by their streamlined bodies and prominent dorsal fins, predominantly inhabit deep offshore waters. Unlike other baleen whales, they exhibit a unique blend of features, including a distinctive dorsal fin shape and specialized feeding habits that set them apart. These whales are adapted to a life in both sub-tropical to sub-polar offshore waters globally, exhibiting flexibility in habitat preference. They thrive in waters that span a wide range of depths, from intermediate to deep oceanic regions, and exhibit a preference for environments that are away from continental shelf waters.

Sei Whale distribution extends to areas with steeply sloping regions around seamounts and deep submarine canyons, showcasing their adaptability to various marine environments. Sei Whales can occasionally be found in waters as deep as 5,000 meters or as shallow as 320 meters, indicating their remarkable versatility and wide-ranging habitat preferences within the world’s oceans.

Quick facts

Length

Male: 15m

Female: 16m

Calf: 4,6m

Weight

Adults: 27 tons

Calves: 700 kg

Habits

Dive Time

<40mins

Dive Depth

+1000m

Reproduction

50-60 (74 max)

Life Span:

11-13mth

Gestation period:

Dive sequence

@Georgina Cabayol

Behavior

Socializing +

Sei Whales are one of the faster rorquals, capable of speeds up to 25km/h, though they typically cruise at 3.7-7.4km/h. They rarely breach, but instances of “belly-flop” jumps may occur. Their social behavior is marked by low-frequency vocalizations, primarily below 1kHz, with more vocal activity observed during daylight hours. This suggests a pattern of social interaction and communication that aligns with their diurnal activities.

Resting +

Information on resting specifically for Sei Whales wasn’t directly extracted from the provided sections of the book. However, like many cetaceans, they may engage in periods of rest that involve slow movements or floating at the surface, possibly utilizing this time for low-energy activities and social bonding within their groups.

Foraging & Diet +

Sei Whales exhibit diverse feeding strategies, including “skimming” near the surface and “lunging and gulping” to capture prey. They adapt their foraging depth based on the time of day, correlating with the vertical migration patterns of their prey, which includes schooling fish, krill, and squid. Dive sequences indicate a methodical approach to surfacing and submerging, with the dorsal fin and blowholes often visible simultaneously, showcasing their adapted feeding and diving techniques to optimize prey capture.

https://wwhandbook.iwc.int/en/species/sei-whale

Distribution & Movements

Sei whales are found in nearly all waters of the world, including polar regions where they feed during the summer. In the Azores they are encountered during the spring months on a regular basis as they complete their northerly migration. Sei whales are the least predictable of the baleen whales, and their migrations are not as extensive. They are known to be fast swimmers; in fact, one individual traveled around 4.100km in just 10 days from the Azores to the Labrador Sea.

Reproduction & Life History

Sexual maturity

Around 8 years of age.
This is a critical period in their life cycle when they become capable of reproduction, contributing to the population’s sustainability.

Gestation period

The gestation period ranges from 10.5 to 12.5 months.
This extended gestation is indicative of the significant investment Sei Whales make in each offspring, ensuring they are well-developed and ready for life in the ocean.

Number of calves

Females typically give birth every 2 to 3 years, allowing them significant time to nurse and wean their calf before reproducing again. This interval helps maintain the health of both the mother and her calf, emphasizing the species’ K-selected reproductive strategy.

Suckling period & Nursing

Calves are weaned after 6 to 8 months, during which they rely entirely on their mother’s milk for nutrition. This period is crucial for calf development, providing them with the necessary fat and nutrients to thrive.

Lifespan

Sei Whales have a potential lifespan of 50 to 60 years, with the oldest recorded individual reaching 74 years. This longevity reflects their slow growth and late maturity, typical of large whale species.

Mating strategy

While specific details of their mating strategy are less documented, the gestation and calving data suggest a complex social structure and reproductive behavior designed to maximize the survival of each calf in the open ocean’s challenging environment.

Specimen that you can see in Azores sea

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Balaenoptera musculus

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Bryde’s Whale

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Balaenoptera physalus

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Minke Whale

Balaenoptera acutorostrata

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

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Pilot Whale (Long & Short-finned)

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Highly social, intelligent & deep divers.

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Blainville’s Beaked Whale

Mesoplodon densirostris

Elusive deep-divers known for their unique foraging behavior.

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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

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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

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Stenella coeruleoalba

Notable for their striking body patterns and acrobatic prowess.

Striped Dolphin

Stenella coeruleoalba

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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.

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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.

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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.

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Mesoplodon bidens

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Grampus griseus

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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

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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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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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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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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

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Nothern Bottlenose Whale

Hyperoodon ampullatus

Nothern Bottlenose Whale

Hyperoodon ampullatus

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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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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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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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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

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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

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Whale Watching in Ponta Delgada

Whale Watching in Rabo de Peixe

Van Tour to Furnas

Jeep Tour Sete Cidades & Lagoa do Fogo

Kayak Rental in Sete Cidades (double)

Bike Rental in Sete Cidades

Whale Watching in Lajes do Pico

Pico Island Van Tour

Hiking Unesco Heritage

Sei Whale

Balaenoptera borealis

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

Quick facts

Length

Weight

Habits

Reproduction

Reproduction

IUCN RED LIST STATUS: Endangered High risk of extinction. Critical conservation required.

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

González García, L. et al (2022): Sympatric baleen whales choose different habitat conditions in São Miguel

Sardà, C. et al (2013): Temporal Distribution of the Most Sighted Baleen Whales in Azores: Fin Whales and Sei Whales

Ojeda, V. et al (2018): Complex Temporal Distribution of Fin Whales and Sei Whales

Ojeda, V. et al. (2019): Baleen Whale Faeces in the Azores: Insights from Whale-Watching Platforms

Borba, M. (2013): Analysis of the spatial intelligence of the presence of mysticetes with oceanic fronts

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

Leal, M. (2021): Photo identification and habitat preferences of a migrant ocean traveller in São Miguel, Azores

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: Endangered

High risk of extinction. Critical conservation required.