Hippopotamus Gestation Calculator
This hippopotamus gestation calculator finds the expected birth date instantly. Select your species and enter the mating date to calculate the gestation period and view key milestones.
Quick Answer
Hippopotamus gestation is 240 days — approximately 34.3 weeks or 7.9 months. Hippo calves are typically born underwater. Enter your mating date above for an exact expected birth date.
Hippopotamus Gestation Calculator
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Birth Underwater
Hippo calves are typically born underwater, and the newborn must instinctively swim to the surface for its very first breath within moments of birth. This underwater birth is a striking adaptation to a species that spends the vast majority of its life submerged in rivers and lakes, only emerging at night to graze on land.
Most Dangerous Animal in Africa
By most measures, hippos are responsible for more human deaths in Africa annually than lions or crocodiles, despite being herbivores. Their aggressive territoriality, enormous size, surprising speed on land, and powerful bite make encounters with humans — particularly boaters crossing hippo-occupied waterways — extremely dangerous.
Closer to Whales Than Pigs
Genetic and fossil evidence shows hippos are the closest living land relatives of whales and dolphins, sharing a common semi-aquatic ancestor roughly 55 million years ago. This makes hippos far more closely related to cetaceans than to pigs, despite superficial resemblance to other large land mammals — one of the more surprising facts in mammalian evolutionary biology.
"Blood Sweat" Explained
Despite the nickname, hippo "blood sweat" isn't blood at all — it's a thick, red-tinted oily secretion produced by glands in the skin that acts as a natural sunscreen and has documented antibiotic and antimicrobial properties. This unique substance helps protect hippos' sensitive, mostly hairless skin during time spent out of water under the African sun.
Hippo calves can nurse while fully submerged by closing their nostrils and ears to keep water out, allowing them to suckle from their mother even while she remains partly or fully underwater — an adaptation few other mammals share to this degree.
Social Structure
A dominant male typically controls a section of river or waterway and mates with the females that live within it, while females often form nursery groups (sometimes called pods or bloats) to protect calves collectively from crocodiles and other threats. Male hippos will fiercely defend their territory, sometimes fatally, against rival males.
Gestation by Hippo Species
| Species | Avg. Gestation |
|---|---|
| Common Hippopotamus | 240 days |
| Pygmy Hippopotamus | 188 days |
How Hippo Gestation Compares to Other Large Mammals
| Species | Avg. Days | Vs. Hippo |
|---|---|---|
| Elephant | 645 days | 405 days longer |
| Rhinoceros | 462 days | 222 days longer |
| Giraffe | 457 days | 217 days longer |
| Hippopotamus | 240 days | — |
See our rhinoceros gestation calculator.
How We Calculate Hippo Gestation
The hippopotamus gestation calculator uses the formula: Birth Date = Mating Date + selected species' average gestation days, drawn from published wildlife biology and zoo husbandry research.
Frequently Asked Questions
How long are hippos pregnant?
Hippos are pregnant for approximately 240 days on average, with a normal range of 225–257 days. Pygmy hippos, a much smaller and more solitary relative, have a notably shorter gestation of around 188 days.
Do hippos really give birth underwater?
Yes — hippo calves are typically born underwater, and the newborn must instinctively swim to the surface for its very first breath within moments of birth. This underwater birth is a striking adaptation to a species that spends the vast majority of its life submerged in rivers and lakes.
Are hippos the most dangerous animal in Africa?
By most measures, yes — hippos are responsible for more human deaths in Africa annually than lions or crocodiles, despite being herbivores. Their aggressive territoriality, enormous size, surprising speed on land, and powerful bite make encounters with humans, particularly boaters, extremely dangerous.
Are hippos related to whales?
Remarkably, yes. Genetic and fossil evidence shows hippos are the closest living land relatives of whales and dolphins, sharing a common semi-aquatic ancestor roughly 55 million years ago. This makes hippos far more closely related to cetaceans than to pigs, despite superficial resemblance to other large land mammals.
What is hippo 'blood sweat'?
Despite the nickname, hippo 'blood sweat' isn't blood at all — it's a thick, red-tinted oily secretion produced by glands in the skin that acts as a natural sunscreen and has documented antibiotic and antimicrobial properties. This unique substance helps protect hippos' sensitive, mostly hairless skin during time spent out of water under the African sun.
How do hippo calves nurse underwater?
Hippo calves can nurse while fully submerged by closing their nostrils and ears to keep water out, allowing them to suckle from their mother even while she remains partly or fully underwater — an adaptation few other mammals share to this degree.
How does hippo social structure work?
A dominant male typically controls a section of river or waterway and mates with the females that live within it, while females often form nursery groups (sometimes called pods or bloats) to protect calves collectively from crocodiles and other threats. Male hippos will fiercely defend their territory, sometimes fatally, against rival males.
How does hippo gestation compare to other large mammals?
At 240 days, hippo gestation is far shorter than the rhino's 462 days, the giraffe's 457 days, and the elephant's 645 days — despite hippos being among the largest living land mammals themselves, their gestation is surprisingly brief by comparison.
Sources & References
- IUCN Red List — Hippopotamus conservation status
- Merck Veterinary Manual — Ungulate reproduction
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Kanika
Researched and reviewed by Kanika, founder of GestationCalc. All gestation data is verified against primary veterinary and agricultural sources before publication.
Last reviewed: September 4, 2026