The Whale Gestation Period: Discover How Long Whales Are Pregnant

Have you ever wondered how long whales are pregnant? With the massive size of whale babies, it comes as no surprise that whales have long gestation periods. Dive in to find out how long whales are pregnant and learn what makes whale pregnancies different. Plus, we’ll compare the different whale species to see which one has the longest gestation period of all.

How Long Are Whales Pregnant?

Whales are the largest creatures in the ocean, so it makes sense that they have some of the longest gestation times. However, the exact gestation period of a whale depends on the species. The average times range between 10 and 18 months.

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 generally take a different approach. Mammals tend to spend more time caring for their children before sending them off on their own. As such, the success rates for mammalian children are much higher than those of clownfish or starfish, for example.

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

Why Do Whales Have Such Long Gestation Periods?

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 longer time in the womb to develop them. Whales are some of the smartest animals in the world, so consequently, they have long gestation periods. One of the smartest members of the whale/dolphin family, the orca, has one of the longest gestation periods of 15 to 18 months.

Another animal with a high level of brain development when they are born is the elephant. Elephants are well-known to be some of the smartest animals to walk the earth, and they have a gestation period of 18-22 months. Humans have it rough at around 9-10 months, but elephant mamas may have to carry their babies for nearly two years.

How Big Are Whale Babies When They Are Born?

As you may have guessed, the exact size of a whale baby depends on the species. Calf size, however, varies widely. The largest whale on the planet, the blue whale, gives birth to calves that are around 23 feet long and weigh between 5,000 and 6,000 pounds. As soon as they are born, they are larger than nearly every other animal on Earth.

Humpback whale calves are about 10 to 15 feet in length and weigh around 3,000 pounds. Minke whales give birth to calves that are 8 to 11.5 feet in length and weigh between 700 and 1,000 pounds. Beluga whale calves are about 5 feet long at birth and weigh between 90 and 130 pounds. The smallest whale species, the dwarf sperm whale, gives birth to calves that measure about 3.3 feet long and weigh only around 30 pounds.

Whale Gestation by Species

Gestation times for some of the most common whale species are listed in the chart below.

How Long Does It Take for Whale Babies to Become Adults?

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. The age at which whales become sexually mature varies widely by species. Many baleen whales, such as humpback whales, mature between 5 and 10 years old, but some species, like the bowhead whale, do not reach sexual maturity until around 20-25 years of age. During this time, whales can reproduce, but they probably aren’t fully grown yet.

In fact, the longest-living marine mammal in the entire world is the bowhead whale. Many scientists believe that the bowhead whale lives upwards of 200 years, meaning that there may be some bowhead whales alive who were around during the first expeditions along the Oregon Trail. Since these whales have such long lifespans, it naturally takes longer for them to mature. Bowhead whales also have the longest gestation period of any whale species. Recent research found that these whales can be pregnant for as long as 23 months.