For humans, the gestation period can last forty weeks. There are cramps, morning sickness, strange food cravings, increasing discomfort, and a multitude of other effects. And the nine months of pregnancy is often just a prelude to the real drama. All this pain and suffering is for a good reason though.
Scientists are still learning more about when live birth evolved, but one fossil discovery in the South China Sea revealed a 250 million-year-old creature with an embryo in its ribcage. The Dinocephalosaurus fossil was an archosauromorph, a group that includes dinosaurs and modern-day birds and crocodiles. Today, birds and crocodiles just lay eggs. But most mammals aside from the platypus and some snakes, lizards, fish, and amphibians give live birth.
An examination of some of these species’ gestation periods reveals that human mothers don’t necessarily have it the worst out there. Some sharks and even a salamander retain their fetuses for years sometimes before giving birth. So, what animal has the longest gestation period? Here are the 5 longest periods in the animal kingdom.
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1. Golden Alpine Salamander Gestation Period: 3 Years
Golden alpine salamanders live in cold climates in mountainous parts of Switzerland. They hold the Guinness World Record for the longest gestation period among amphibians. Mothers usually harbor their young for about three years before giving birth, though in some cases, post-term for these creatures can mean a whole extra year.
The species adapted to give live birth during the Ices Ages, when warmer water to lay eggs wasn’t as easy to come by, says Antonio Romero, a biologist with Italy’s National Research Council who studies the species.
“The long gestation and viviparity of [the alpine salamander] are closely linked to historical glaciations because these adaptations provided survival advantages in cold, harsh environments,” Romero says. The cold also meant everything slowed down.
“Alpine salamanders evolved a multi-year gestation because slow metabolism reduces energy demands, making it possible to sustain developing embryos for years,” he says.
This doesn’t always mean a relaxed, nurturing environment to develop though. Romero says that there are initially several embryos inside the mother, but some will consume the others for nutrition during gestation, leaving only one or two to fully develop. Other amphibians including fire salamanders, Lanza’s alpine salamanders, hellbenders, Anderson’s salamanders and the olm can all have gestation periods longer than humans as well, depending on the weather, he says.
Read More: How Pregnancy Tests Have Evolved Throughout History
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2. Frilled Shark Gestation Period: Almost 3 Years
Several shark species have evolved to give live birth, and the gestation period of some of these can last exceptionally long. The frilled shark, also known as the lizard shark, has a gestation period of at least three years.
With their many gill slits, strangely shaped mouth and eel-like shape, deep-sea sharks are something of a relic from a past era — “It is assumed to represent an ancient morphotype of sharks,” stated Faviel López-Romero and his coauthors in a study on the embryos of the species.
But this research found that some of the strange looks of these sharks happen in the late stage of the embryonic development. The position of the jaws may not be leftover traits from a bygone era, but a more recent adaptation, evolutionarily speaking.
This species isn’t the only shark with long pregnancies. The spiny dogfish’s gestation period lasts about two years.
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3. Elephant Gestation Period: 22 Months
Elephants may be the champion mothers of the land-walking mammals. Elephant embryos gestate for 22 months, time enough to help them grow into young giants — elephants weigh around 240 pounds at birth. It also gives them a head start in the brains department, as elephant newborns have relatively good cognitive skills.
This long gestation period may happen in elephants because they have something that other mammals lack. All mammals have a corpus luteum, a temporary gland that remains after an egg follicle is released during menstrual cycles. These glands stick around for a while during pregnancy, releasing important hormones that help the embryo develop. While most mammals only have one of these open at a time, elephants can have as many as 12 open during their pregnancies, according to research published in Biological Sciences.
They increase in size as the embryo develops, after a slow beginning. “Our findings demonstrate a highly successful reproductive solution, different from currently described mammalian models,” the authors of the study stated.
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4. Orca Gestation Period: 15-16 Months
Many of the other long-gestating mammals are marine-based rather than land-based. Walruses gestate for 15 months to 16 months, while several species of whales have pregnancies that last more than a year. Orcas are among the longest carrying whale mothers, with gestation periods that last around 17 months to 18 months.
In terms of weight, orcas get more done than elephants in a shorter time, producing calves that weigh about 400 pounds. This long gestation makes for a lot of time for things to go wrong, at least in some orca populations.
Hormone work has revealed that more than two-thirds of southern resident orca pregnancies in the Pacific Northwest fail — many late in gestation or right after birth — though this may be due in part to food stress because of drops in the salmon population.
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5. Lizard and Snake Gestation Periods: 12 Months
Most snakes don’t have long gestation periods, but northern copperheads can be pregnant for up to nine months, and could give birth to up to 10 offspring. Some species of lizards, on the other hand, can go a little longer.
The Mabuya skink of Brazil, for example, can gestate for up to 12 months. Females carry between two and nine embryos. Other skinks may also have similarly long pregnancies, but the stumpy-tailed lizard in Australia may have one of the most uncomfortable pregnancies. Their embryos grow until they are about a third the size of their mothers — roughly like human mothers giving birth to a six-year-old.
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Joshua Rapp Learn is an award-winning D.C.-based science writer. An expat Albertan, he contributes to a number of science publications like National Geographic, The New York Times, The Guardian, New Scientist, Hakai, and others.
