Hippopotamus (Hippopotamus amphibius) & Pygmy Hippopotamus (Choerpsis liberiensis) Fact Sheet: Reproduction & Development

• Possession of a territory pre-requisite to mating
  • Bulls controlling the most desirable territories have most reproductive success
  • Non-territorial bulls (90%) are excluded from reproducing
• Females seasonally polyestrous (lasts 3 days). Males show no evidence of sexual fluctuations
• Mating peaks during dry spells (population most concentrated)
• Mating in water for both species; Pygmy Hippos also mate on land
• Copulation lasts up to one half hour. Female is fully submerged (raises her nose above water periodically)
• Courtship often accompanied by male's wheeze-honking sound

Reproductive rate

• Under good conditions, females can produce a calf each year
• Comparatively high for such a large animal

Gestation

• Common Hippos: 227-240 days
• Pygmy Hippos: 188 days

Birth

• Birth Weight
• Common Hippo: 25-55 kg (55-121 lb)
• Pygmy Hippos: 5.73 kg (12.7 lb)
• Litter Size: one, twins rare
• Female aggressive prior to giving birth
  • Leaves herd
  • Returns in 10-14 days after calf has imprinted on her
  • Imprinting phase also common in other ungulates such as horses and zebras
• Common Hippo birth occurs on land or in shallow water, usually in October or April (during rains)
• Pygmy Hippos born on land throughout year
• Birth occurs hind legs first
  • Common Hippo calf may have to push off from bottom and come to surface for its first breath
  • Adaptations for underwater nursing: ears automatically fold and nostrils close (even when nursing on land).
  • Frequently surface to breathe
    

Young of the year (< 1 year old)

• Calves remain in water when mother leaves to forage; mother returns periodically to let calf nurse
• Infants can remain underwater only about 2 minutes
• Normally breathe about every 30 seconds
• Indirect evidence that during poor environmental conditions, nursing period is extended and calves suckle more than one cow
• Lactation lasts approximately 1 year
• Grazing begins at 1 month; substantial grazing at 5 months
• Weaned at 6-8 months for both species
• In wild, occasional infanticide by adult or juvenile males

 Juveniles

• Until about one year, calves vulnerable to Nile Crocodile attacks
• Young remain with mother for several years

 Adults

• Sexual maturity in managed care much younger than reported for wild
  • In managed care: 3-4 years
  • In the wild: males 6-13 yrs.; females 7-15yrs.
  • It is unlikely that young bulls are allowed to breed effectively until much older
• Fertility doesn't' decrease much with declining age
  • Many females still can reproduce in 30s and 40s
• Psychological maturity in the wild is probably about 20 years

Managed care

• Common hippo
  • Median life expectancy
    • 36.6 years (AZA 2023)
• Pygmy hippo
  • Median life expectancy
    • 27.6 years for females (AZA 2023)

• Vulnerable to predation by Nile crocodiles, hyenas, and lions while young and small

Young hippo calves are able to dive for about two minutes.

Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Kingdon (1979)
Klingel (1991)
Nowak (1991)
Smuts & Whyte (1981)