By Lucy Adlard

The Reproductive System of
☯ the Blue Whale ☯

☆Habitat and Environment☆

Blue whales are the largest creatures on earth. They inhabit all oceans in the world and prefer cold, deep waters.  Blue whales are mammals, but they spend their whole life in the water. This means they need to have a way to get oxygen and breathe without gills. The blue whale has many adaptations that allow it to survive in its environment. The blue whale not only has blubber for warmth, and a streamlined shape for swimming, it has a feature that does not allow it to sleep. If they slept, they would drown, so they only take short naps. Whales also have a way of reproducing in the water without laying eggs, unlike the majority of other aquatic creatures. The male blue whales' reproductive organs are enclosed inside the skin folds to protect them whilst swimming.

This image shows where Blue Whales are found, where the breed and where they migrate.

This Ted-Ed Video explains a little bit more about blue whales, their size and evolution.

☮ Fertilisation ☮

Blue whales cross fertilise internally, with another blue whale of the opposite sex. That means they reproduce sexually. A female blue whale produces eggs inside her ovaries and will release one into her fallopian tubes much like a human. When it meets with the male gamete (sperm) they fertilise and form a zygote which will burrow into the uterus of the female and begin to form into a baby whale. This process of fertilisation is very similar to a humans. Both blue whales and humans fertilise internally. Internal fertilisation is practical for whales as it means the embryo has more protection inside the mother's womb.

Development and Birth

Once fertilised, the zygote buries itself into the lining of the female blue whale uterus. It develops internally inside the womb for 11-13 months- Blue whales are viviparous. Sometimes mother whale will intentionally leave their baby inside for longer to be sure the calf is fully developed. Calves develop internally so they are protected and can get oxygen and nutrients, as even though they are aquatic mammals blue whales still need air. Similarly to humans, an umbilical cord connects the mother to the baby, providing it with the things it needs. When the calf is born it comes out tail first, and swims straight to the surface to breathe so it won't drown. The mother usually migrates to a warmer, shallower sea to give birth.

A mother blue whale and her calf

⚜ Parental Care ⚜

Once a male and female blue whale mate they stay together for the rest of their lives. The blue whale newborn is about 7 metres in length and weighs about 2.5 tonnes.  It eats nothing but it's mother's milk and gains about 91 kilograms every day for its first year. Usually only one calf is born at a time, but there have been reported cases of twins! The calf is looked after extensively by it's mother for 2-3 years, but the father does not contribute much to caring for the calf. Whales have been known to live up to 110 years old, and infant mortality is very rare, as the mothers protect their babies until they are old enough to fend for themselves. This is necessary because whales do not become sexually mature until they are 10 years old and need constant caring for until they are 2-3, so they have gathered enough skills and knowledge to survive without their mother and continue reproducing. Whales use K-Selection because they live in a relatively stable environment and they only produce one offspring that they care and look after for very well.

❀ Facts about Blue Whales ❀

  • The scientific name of the blue whale is Balaenoptera musculus.
  • Their average lifespan in the wild is 80-90 years, although some have been known to live for up to 110 years.
  • Blue whales are usually between 25 to 32 metres long.
  • Adults can eat 3.6 to 7.3 metric tonnes of krill per day.
  • They can weigh about 181,437 kilograms. That is more than 40 elephants!
  • Females are larger than males.
  • The blue whale's heart weighs as much as a small car.
  • Its tongue can weigh two to three tonnes.
  • When a blue whale exhales, the spray from its blowhole can reach nearly 9 metres into the air.

The blue whale in comparison to a bus and a gray whale


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