Whales are marine mammals and share many of the same characteristics that are common among almost all mammals including, the need to breathe air (whales get their oxygen above the surface of the water), being warm-blooded (whales have thick layers of blubber to keep them warm), having hair (some species have hair at birth) and giving birth to their young (not laying eggs as most fish and amphibians do).
Regarding reproduction and length of pregnancy from conception to birth, female whales’ gestation period is very similar to human pregnancy in several ways. In fact, it is nearly identical to human birth, with the exception that a whale’s gestation period can last significantly longer than a human’s, depending on the whale’s species.
Average gestation period
So how long is the average gestation period for a whale? Depending on the whale species, the average gestation period can range anywhere from 10 – 18 months. While some species can mate throughout the year, the most common time of year for whales to mate/bear offspring is during the colder winter months when various species travel to the warmer tropical environments to mate and give birth.
During mating season, males will compete for the right to mate with the female. The aggression and dominance displayed by the whales will vary from one species to the next, with some males fighting one another or showing off while others appear fairly relaxed and carefree.
Some species will show their youthfulness by performing various acrobatic stunts, charging one another, and displaying dominance. Other species will sing to attract a mating partner or herd off the female so that competing males have less chance to mate with her.
In a single season, it isn’t uncommon for a female to mate with several males to maximize her chances of bearing a healthy child; in fact, some male species will attempt to wash the competing male’s sperm out by producing significant amounts of their own sperm.
Once the female becomes impregnated, she spends 9 – 18 months developing and carrying her child in her uterus (womb). After several mating months, these marine mammals will travel back to their feeding grounds until the next mating season.
Note: While numerous whale species migrate from one location to the other to give birth and feed, not all species are known for making long migration trips, and some whales will stay within their local habitat all year long.
During this time (when the female becomes impregnated), the female whale will go through a gestation period where her child develops in her uterus. As the child develops, it is given nutrient-rich blood through an umbilical cord until it is fully developed and ready to be born. Also, to provide the child with nutrients, the umbilical cord will help remove waste from the child to make sure the baby is growing healthily.
Once birth occurs, the umbilical cord is separated, leaving the baby whale with a belly button, just like in humans. After birth, the female whale feeds her young by producing milk from her mammary glands, which the young baby whale receives from the mother’s nipple.
Most baby whales will continue to receive nutrients from their mother’s milk nipple for 6 months to 2 years, depending on the species. This nursing period continues until the young whale can hunt for food independently.
In some situations, a young whale will continue to suckle from the mother’s nipple even when the mother stops lactating and producing milk. In these cases, young whales often form a psychological dependency that takes longer than average to grow out of; however, eventually, all young whales separate from this psychological bond.
After several years of hunting and living independently, the young whales reach sexual maturity and are ready to find other whales to mate with. The age of sexual maturity can range from 5 to 20 years for these marine mammals, depending on the whale’s species and sex.
After sexual maturity occurs, these whales will then repeat their parents’ process and begin mating and bearing their own offspring to pass along their genes to the next generation. Depending on the whale’s species, habitat, health, and social environment, a whale’s average lifespan can vary from 20 – 200 years.
Marine mammals that have been held in captivity are known to have significantly shorter lifespans than those in the wild due to a combination of their diet, small living space, and lack of social community. For example, the killer whale is known to have a lifespan of 40 – 70 years in the wild. However, those held in captivity usually don’t live past their 20’s.
Many whale species have been known to have lifespans of 30 – 80 years, with a few species living up to 100 years and one species, “the bowhead whale,” having a lifespan of up to 200. If you would like to learn more about whales’ average lifespan, check out: How long do whales live?
Gestation period comparisons
To give you a better idea of how long it takes for whales to reproduce once impregnated, here are the gestation periods of various whale species:
- Minke Whale: 10 months (females average 1 offspring about every 2 years).
- Narwhal Whale: 14 – 15 months (limited data suggests females bear 1 offspring every 3 years).
- Sperm Whale: 14 – 16 months (females reproduce every 3 – 6 years).
- Gray Whale: 13.5 months (data not available)
- humpback whale: 11 – 12 months (reproduction occurs every 2 – 3 years).
- Beluga Whale: 14 – 15 months (females give birth to a single calf every 3 years).
- Blue Whale: 11 – 12 months (females breed every 2 – 3 years).
- Killer whale: 15 – 18 months (average is about 17 months). Females give birth every 3 – 5 years.
Note: Killer whales are part of the dolphin family and are the largest among the dolphin species. They are not whales, as their name may suggest. As you can see, there is a large variation in terms of the gestation periods of different cetaceans.
While this may not be the case, it appears that whales who follow regular migrations from their mating grounds to their feeding grounds tend to have a gestation period of around 11 – 13 months, while species that do not have a particular mating location or live in the same environment throughout the year may have more sporadic gestation lengths.
This may make sense as whales that travel from cold environments to warm tropical areas between seasons need to maintain a seasonal gestation length to not give birth in an unnatural location for their reproductive needs.