Whale Gestation Period: How Long Are Whales Pregnant?

humpback whale
© Imagine Earth Photography/Shutterstock.com

Written by Colby Maxwell

Published: September 29, 2022

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Whales aren’t just big creatures, they have gestation periods much longer than a human! With the massive size of whale babies, it definitely makes sense. Let’s dive into how long whales are pregnant and learn what makes them special. Plus, let’s compare the different species of whales and see which one has the longest gestation period of all! Let’s get started.

How Long are Whales Pregnant?

mother and baby humpback whale swimming together

Mother and baby

humpback whale

swimming together

©Imagine Earth Photography/Shutterstock.com

The exact gestation period of a whale depends on the species, but the average times are anywhere between 10 and 18 months.

Whales are the largest creatures in the ocean, so it makes sense that they have some of the longest gestation times! Part of what makes whales so special is that they are marine mammals, not fish. Fish lay lots of eggs and hope that a few of them survive to adulthood. Mammals usually take a different approach. Instead of “shotgunning” their kids into the world, mammals spend a lot more time caring for and developing their children before sending them off on their own. As such, the success rates for mammal children are much higher than that of clownfish or starfish, for example.

Additionally, mammals carry their young for much, much longer than creatures who lay eggs. In the case of whales, carrying their young is an especially long process. When a whale mother does give birth, however, it’s to a fully functioning whale baby, albeit a small one.

Why do whales have such a long gestation period?

Whale Gestation Period: How Long Are Whales Pregnant?

Whales are large and have advanced brains, both of which require a longer gestation period.

©CampCrazy Photography/Shutterstock.com

Part of the reason that whales, along with most mammals, have longer gestation periods is because of brain development. Overall, mammals have much more advanced brains and need a long time in the womb to develop them. Whales are some of the smartest animals in the world and consequently, have long gestation periods. Even more, potentially the smartest member of the whale/dolphin family, the orca, has the longest gestation of 15-18 months.

Other animals with a high level of brain development when they are born are creatures like elephants. Elephants are well-known to be some of the smartest animals to walk the earth and consequently, have a gestation period of 18-22 months. Humans have it rough (around 9 months), but elephant mamas have to carry their babies for nearly two years!

How big are whale babies when they are born?

Whale Gestation Period: How Long Are Whales Pregnant?

A Humpback Whale with her calf in the

Pacific Ocean

. A

humpback whale

baby is weaned at around seven months when it begins to eat small fish and other sea creatures.

©Imagine Earth Photography/Shutterstock.com

The exact size of a whale baby depends on the species. The largest whales on the planet, the blue whale, give birth to calves that are around 23 feet long. As soon as they are born, they are larger than nearly every animal on earth. The smallest species of whale, the dwarf sperm whale, is usually 9 feet long when it’s an adult, with their babies usually measuring 4 feet long and weighing 400-600 lbs.

Regardless of the whale, their babies are truly massive when born and all clear 400 lbs. The smallest whale babies are significantly larger than the largest humans! Even still, whale babies are at risk of predation when they are born. Only when they reach full size do they fully become the kings of the ocean.

Whale Gestation by Species

Let’s go over a few of the most common whales and their associated gestation times in the chart below.

Whale SpeciesGestation
Sperm whale14-16 months
Orca15-18 months
Humpback whale11 months
Beluga whale12-14 months
Blue whale10-12 months
Narwhal14 months
Fin whale11 months
Gray whale12 months
Common minke whale10 months
Dwarf sperm whale274 days
Short-finned pilot whale15 months
Southern right whale12 months
North Atlantic right whale12 months
Sei whale11 months
Baiji10 months
Long-finned pilot whale16 months
Northern bottlenose whale12 months
Sowerby’s beaked whale12 months
Baird’s beaked whale13 months

How long does it take for whale babies to become adults?

Whale Gestation Period: How Long Are Whales Pregnant?


bowhead whale

is the longest-lived marine mammal in the world.

©NOAA Photo Library / public domain – Original / License

As a general rule, the exact time that a whale takes to mature from birth depends on the species. Still, there are some averages we can look at.

On average, whales become sexually mature between 5-10 years. During this time the whales are able to reproduce, but they probably aren’t fully grown yet. Some species of whales take around 25 years to reach maturity, however. The longest-living marine mammal in the entire world, in fact, is the bowhead whale. Many scientists belive that the bowhead whale lives upwards of 200 years, meaning that there may be some bowheads alive who were around before Maine was a state and during the first expeditions along the Oregon Trail.

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About the Author

Colby is a writer at A-Z Animals primarily covering outdoors, unique animal stories, and science news. Colby has been writing about science news and animals for five years and holds a bachelor's degree from SEU. A resident of NYC, you can find him camping, exploring, and telling everyone about what birds he saw at his local birdfeeder.

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