Incubation refers to the process by which certain animals hatch from eggs. The length of incubation varies widely across different animal species. Some animals, like chickens, hatch in just a few weeks. Others, like elephants, can take up to 2 years to incubate!
So which animal has the longest incubation period? Let’s take a look at some of the contenders.
Elephants
Elephants have one of the longest gestation periods of any mammal. After mating, a female elephant is pregnant for an incredible 22 months, or about 660 days, before giving birth.
Baby elephants, called calves, weigh around 100 kg at birth. With such a long incubation and large size, elephant calves are relatively well developed and mobile from the moment they are born.
The African bush elephant specifically has an average incubation period of 645 days according to most sources. For the Asian elephant subspecies, gestation may last anywhere from 617 to 690 days on average.
Frigatebirds
Frigatebirds have the longest incubation period of any bird. There are five different species of frigatebirds, but they all have similarly lengthy incubations.
The great frigatebird has the longest incubation at around 56 days. Other frigatebird species incubate for 49 to 55 days typically.
These large seabirds have slow chick development overall. Frigatebird chicks take so long to fledge that they can spend up to 22 weeks in the nest before they are ready to fly.
Brown kiwi
Brown kiwis stand out for having one of the lengthiest incubation periods of any bird relative to their body size. On average, female brown kiwis incubate their eggs for around 70 to 84 days.
Since kiwis are flightless, they invest a lot of resources in their chicks. Kiwi chicks hatch fully feathered and are soon able to leave the nest.
Other kiwi species, like the great spotted kiwi, have shorter but still impressive incubation periods of 65 to 90 days.
Emperor penguin
The emperor penguin wins the prize for the longest incubation period of any bird. Female emperor penguins lay a single egg and then promptly leave it in the care of the male while she hunts for around two months.
Male emperor penguins cradle the egg on their feet and incubate it beneath a flap of skin known as the brood pouch. Incubation lasts for around 64 to 67 days until the chick hatches.
This extremely long incubation is essential to ensure the egg hatches during the brief Antarctic summer when food is abundant.
Leatherback sea turtle
Leatherback sea turtles have the longest incubation period of any reptile, averaging around 60 to 70 days. Larger leatherback clutches may incubate for up to 90 days.
The embryos develop more slowly because leatherback nests are dug deep in the sand where temperatures are cooler. This helps offset the nests being heated by the sun in tropical beach habitats.
Other sea turtle species have much shorter incubations of 45 to 60 days typically.
Pythons and anacondas
Some of the largest snake species have exceptionally long incubation periods. Reticulated pythons carry their eggs for around 90 days before they hatch.
Green anacondas seem to have the longest incubation of any snake. They’ve been observed incubating eggs for anywhere from 6 to 8 months in the wild!
Alpine salamander
The alpine salamander wins the record for the longest incubation period of any amphibian. Eggs may require 2.5 to 4 years of incubation before hatching.
Alpine salamander eggs develop very slowly due to the cold temperatures of the high altitude mountain environments where they are laid.
Most amphibians have relatively short incubations lasting several days or weeks. But cold adaptation allows alpine salamanders to push incubation to multi-year lengths.
Ocean quahog clam
When it comes to invertebrate animals, a species of clam called the ocean quahog has an extraordinarily slow incubation time.
Ocean quahogs are very long-lived clams found in the North Atlantic. They lay down growth rings on their shells and some specimens have been aged at over 500 years old!
In these clams, eggs take 10-12 months to fully develop before larvae hatch. Some other clam species incubate for 3-5 months.
Conclusion
Based on the longest verified incubation periods, the animal that takes the longest to incubate is the ocean quahog clam at 10-12 months.
Some snakes and salamanders may incubate eggs longer, but exact data for wild snakes is limited. Elephants also have remarkably lengthy incubations at up to 22 months.
Incubation gives embryos time to fully develop, especially in harsh environments like the deep ocean or ice-covered Antarctica. But the ocean quahog takes especially long, allowing their larvae ample time to mature within the shells.
Ultimately, incubation length is tied to an animal’s reproductive strategies and habitat. For the quahog clam, their extreme longevity selects for equally prolonged early development as part of their life history.
References
Elephant incubation
- African Bush Elephant. San Diego Zoo. https://animals.sandiegozoo.org/animals/elephant-african
- Asian Elephant. San Diego Zoo. https://animals.sandiegozoo.org/animals/asian-elephant
Frigatebird incubation
- Great Frigatebird. Audubon. https://www.audubon.org/field-guide/bird/great-frigatebird
- Magnificent Frigatebird. Audubon. https://www.audubon.org/field-guide/bird/magnificent-frigatebird
Kiwi incubation
- Brown Kiwi. San Diego Zoo. https://animals.sandiegozoo.org/animals/kiwi-brown
- Great Spotted Kiwi. San Diego Zoo. https://animals.sandiegozoo.org/animals/kiwi-great-spotted
Emperor penguin incubation
- Emperor Penguin. SeaWorld. https://seaworld.org/animals/all-about/emperor-penguin/
Leatherback sea turtle incubation
- Leatherback Sea Turtle. National Wildlife Federation. https://www.nwf.org/Educational-Resources/Wildlife-Guide/Reptiles/Leatherback-Sea-Turtle
Python and anaconda incubation
- Reticulated Python. National Geographic. https://www.nationalgeographic.com/animals/reptiles/facts/reticulated-python
- Green Anaconda. National Geographic. https://www.nationalgeographic.com/animals/reptiles/facts/green-anaconda
Alpine salamander incubation
- Alpine Salamander. AmphibiaWeb. https://amphibiaweb.org/cgi/amphib_query?where-genus=Salamandra&where-species=atra&account=amphibiaweb
Ocean quahog clam incubation
- Arctica islandica. Animal Diversity Web. https://animaldiversity.org/accounts/Arctica_islandica/