Sei Whale

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:

Physical characteristics

Group Structure

Sei Whales exhibit a flexible social structure that varies with their environmental context and food availability. They are typically observed traveling alone or in small, fluid groups ranging from 2 to 5 members, but in areas rich in food, they can form larger congregations. These larger groups, though rare, can consist of loosely associated individuals numbering in the tens and occasionally engage in coordinated behaviors possibly related to feeding or social interactions.

The formation of these aggregations suggests a complex social dynamic that allows for temporary alliances in response to ecological conditions, highlighting the adaptability and social intelligence of Sei Whales. This behavior underscores their capacity for both solitary and social living, adapting their group structures in response to their immediate environment and the availability of prey.

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.

Predators

Killer whales are identified as the primary predators of Sei Whales, with many individuals bearing scars from such attacks, indicating encounters that are not uncommon. Additionally, large sharks are known to prey on the calves, suggesting a vulnerability among the younger members of the species to predation. This predation risk underscores the survival challenges Sei Whales face in their natural habitats, particularly for the younger, more vulnerable calves. The presence of these scars not only provides evidence of the interactions between Sei Whales and their natural predators but also highlights the resilience and survival strategies these majestic creatures employ in the face of such threats.

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.

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

Balaenoptera musculus

View profile

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

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

Minke Whale

Balaenoptera acutorostrata

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

Minke Whale

Balaenoptera acutorostrata

View profile

Nothern Bottlenose Whale

Hyperoodon ampullatus

Nothern Bottlenose Whale

Hyperoodon ampullatus

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

Blainville’s Beaked Whale

Mesoplodon densirostris

Elusive deep-divers known for their unique foraging behavior.

Blainville’s Beaked Whale

Mesoplodon densirostris

View profile

Sei Whale

Balaenoptera borealis

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

Sei Whale

Balaenoptera borealis

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

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

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

Striped Dolphin

Stenella coeruleoalba

Notable for their striking body patterns and acrobatic prowess.

Striped Dolphin

Stenella coeruleoalba

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

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

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

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

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

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

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

Whale Watching Azores Essentials

Explore, Love, and Protect: Unveiling the essence of Whale Watching in the Azores

More information

Explore Azores

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

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

González, 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

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

Blainville’s Beaked Whale

Mesoplodon densirostris

Sei Whale

Balaenoptera borealis

Sei Whale

Balaenoptera borealis

Cuvier’s Beaked Whale

Ziphius cavirostris

Cuvier’s Beaked Whale

IUCN RED LIST STATUS: Endangered

High risk of extinction. Critical conservation required.