Animal Gestation Period: Which Species Has the Longest Duration of Pregnancy?

In the animal kingdom, reproduction occurs in different ways. Some of them reproduce sexually, while others are capable of asexual reproduction through fragmentation, budding, or parthenogenesis.

The period between fertilization and birth is known as the gestation period or pregnancy, and it also varies across different animal species. Here are six animals with remarkably long gestation periods.

1. Walrus (Odobenus rosmarus)

The walrus is a large marine mammal distributed throughout the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. This huge, seal-like mammal has the longest gestation period of all pinnipeds, being pregnant for almost 16 months.

Since walruses dwell in the Arctic, they need a large amount of blubber to ensure the survival of their infants. Baby walruses have a high-fat percentage and lower metabolic rate, so they need a more extended gestation period.

2. Killer Whale (Orcinus orca)

These marine mammals give birth to one calf at a time, with a gestation period of about 17 months. They use this long gestation period to grow well before birth, at an average of 8 feet (244 centimeters) in length and 353 pounds (160 kilograms) in weight.

3. African bush elephant (Loxodonta africana)

This animal is considered the largest of all species of living elephants. With a gestation period of 22 months, these enormous creatures have the longest gestation period of any mammal.

Long developmental periods are commonly observed in highly intelligent animals. Since elephants are both the largest living and the biggest-brained land animals in the world, there is a lot of development for baby elephants to do in the womb.

4. Alpine Salamander (Salamandra atra)

The Alpine salamander is a shiny black salamander found in the French Alps and throughout mountainous regions in Europe. At 38 months, it holds the record for having the longest gestation period for amphibians and terrestrial vertebrates.

The average gestation period for this mountain-dwelling newt is two to three years. At higher elevations, however, gestation can extend up to four or even five years.

5. Eel-Like Frilled Shark (Chlamydoselachus anguineus)

The gestation period of Chlamydoselachus anguineus is the longest known for all vertebrates. A group of Japanese scientists discovered that this species' pregnancy may last as long as 42 months (three and a half years), with the embryos' growth rate at around 10-17 millimeters per month. This extended gestation period is believed to be due to the intense cold of its deep-sea habitat, which slows its metabolic processes.

6. Deep-Sea Octopus (Graneledone boreopacifica)

Experts from Monterey Bay Aquarium Research Institute in California spied on an adult female using a remotely operated vehicle. They monitored her as she brooded her hoard of 160 eggs on a rocky ledge 4,593 feet (1,400 meters) down the northern Pacific.

Within a few years, the vehicle returned to that location 18 times and discovered the same female, identified by her distinctive scars, in the same spot, with her arms protectively wrapped around her developing eggs.

As the brood grew stronger, the mother was found to grow weaker. On the final visit, the fully grown larvae had dispersed, and the dead female had floated into the abyss. The mother's marathon brood lasted 53 months (four and a half years), making it the longest brooding period or 'pregnancy' of any known animal.