Sei whales can be broken down into two sub species: the northern sei whale and the southern sei whale.
These whales are the third largest known whales in existence reaching lengths of up to 60 feet.
They are also one of the fastest.
These whales can reach speeds in excess of 30 miles per hour for short bursts/periods of time.
Physical Characteristics and Appearance
Adult male sei whales usually grow to be 40 – 50 feet long and weigh as much as 100,000 pounds, while female whales generally grow to be a bit larger than their male counterparts.
These whales have a dark bluish-gray appearance with a lighter pale under-body.
Their skin is often covered in scars that become apparent after healing from being attacked or injured.
The dorsal fin is tall and located near the rear end of the whale about 2/3 down its back.
These whales have 300 – 400 baleen plates on each side of its mouth which measure about 19 inches long per plate.
Diet and Hunting Methods
Sei whales are filter feeders and attack their prey by opening its mouth and swimming towards its prey with its mouth open.
Once its prey is captured it then pushes the water out of its mouth while keeping its food trapped in the baleen plates.
They are big eaters and are able to consume as much as 2,000 pounds of food per day.
During feeding periods these whales may dive for up to 20 minutes while searching for food.
Habitat and Migration
The sei whale can be found swimming in all of the worlds major oceans, however certain populations may be more abundant than others.
Most sei whales appear to prefer living in moderate temperate cool to warm waters rather then in the freezing polar or hottest tropical regions of the world.
Migration for the sei whale typically involves traveling to cooler waters during the warmer summer months in order to obtain food and build up their supply of blubber.
During the colder winter months these whales will travel towards the warmer tropical/sub tropical environments where they and mate and give birth to their offspring.
Previously before the whaling era these marine mammals were a much more abundant species throughout the world, however extensive hunting has caused significant decreases in certain sei whale populations.
Social Structure and Communication
Sei whales are largely solitary animals although they may be seen swimming in small pods of up to 6 at times and on rare occasions may increase to around 50 or more during certain feeding periods.
These whales are known for creating very loud low-pitched sounds.
As of current not much is known about why these sounds are created.
Little is known about the social structure of sei whales or their relationships to one another regarding whether or not they bond or develop long-term relationships.
Reproduction and Lifespan
The mating season for these marine mammals occurs during the winter months where they spend several months mating and giving birth to offspring.
During their reproductive cycle the average gestation period (the period from conception to birth) for sei whales lasts 11 – 13 months.
Female sei whales bare a single offspring once every 2 – 3 years and on rare occasions twins may be born.
Once born the mother will nurse her child and look after it and may continue to feed the calf milk for up to 9 months.
Maturity is typically reached at around 7 – 11 years which is when these whales can begin mating and reproducing, however they do not reach full maturity until .
The average lifespan for sei whales is 50 – 70 years.
Due to their large size and relatively wide distribution these marine mammals may face a number of possible thetas.
In highly commercialized areas these whales may be threatened by potential collisions with large ships or boats.
In areas where commercial fishing is extremely competitive over fishing causing some populations to relocate or face difficulties maintaining their food supply.
Water pollution can also be a major concern in certain areas.
Oil spills, toxic chemicals and garbage can either affect the whales health directly or through the sources of food they eat.
While these marine mammals are a protected species they may face occasional threats from whalers or poachers.
In regards to natural threats the only marine mammals known to hunt these large whales is a pod of killer whales.
Note: When a sei whale feels threatened or startled it is estimated that they can reach speeds of up to 35 mph for short periods of time in order to escape a life threatening situation, however some estimates claim speeds of up to 40 mph.
10 Intriguing sei whale facts
1) The sei whale is the 3rd largest living animal on this planet after the blue whale and fin whale.
2) Because the sei whale is a marine mammal it is warm-blooded, produces milk, gives birth and breathes air.
3) The scientific name for the sei whale is, “Balaenoptera borealis”.
4) These marine mammals make up one of around 80 known species of cetacea (cetaceans include all species of whale, dolphin and porpoise).
5) The sei whale can be found in all of the worlds major oceans, however they tend to avoid extremely cold/hot climates near the polar and tropical regions of the world.
6) Due to extensive whaling efforts during the whaling era these marine mammals are now considered an endangered and protected species. (It is estimated that nearly 2/3 of their population was decimated due to whaling).
7) The only known potential natural predators of the sei whale is a pack of killer whale.
8) Aside from natural predators sei whales also face threats from collisions with ships, accidental catches in fishing nets and hazards with other fishing gear.
9) Because the sei whale is a baleen whale it is born with two blowholes and lacks teeth, which are instead replaced with up to 400 baleen plates packed with bristles that are used to filter their prey from the water.
10) The sei whale has been recorded holding its breath for up to 20 minutes, however their maximum underwater time is unknown.