The common hippopotamus is one of Africa's most recognizable megafauna — and one of its most poorly understood. Despite an imposing physical presence, hippos occupy a precarious position on the IUCN Red List, and recent research has revealed startling gaps in what scientists know about where populations persist and how fast they are declining [Lacy et al. 2025]. This Species Spotlight examines the hippopotamus's remarkable biology, the pressures threatening its survival, and the coordinated conservation work underway to secure its future across sub-Saharan Africa.
Biology and Identification
Hippopotamus amphibius is the third-largest land mammal on Earth, surpassed in mass only by the African elephant and the white rhinoceros. Adult males typically weigh between 1,500 and 1,800 kilograms, with exceptional individuals exceeding 2,000 kg; females are considerably smaller [Kingdon 1997]. The body is barrel-shaped and nearly hairless, with gray-brown to pinkish skin. A notable physiological feature is a reddish, oily skin secretion — sometimes called "blood sweat" in popular writing — that contains compounds functioning as both a photoprotective sunscreen and a broad-spectrum antimicrobial agent [Saikawa et al. 2004].
The skull is large and dorsoventrally flattened, with eyes, ears, and nostrils positioned high on the dorsal surface — an arrangement that allows near-complete submersion while maintaining sensory contact with the surroundings. Lower canine teeth (tusks) in adult males can exceed 50 centimeters in length and are deployed during intraspecific competition between males [Kingdon 1997].
Hippos are semi-aquatic, spending most daylight hours submerged or resting at the water's edge for thermoregulation. Grazing occurs almost exclusively at night, when individuals travel established paths to nearby grasslands. Adults are capable of brief bursts exceeding 30 km/h on land [Estes 1991]. Females and immature animals associate in groups (commonly called pods); adult males typically hold and defend stretches of water from other males.
Habitat and Range
The common hippopotamus is distributed across sub-Saharan Africa, with the largest concentrations found in East and Central African countries including Uganda, Tanzania, the Democratic Republic of Congo, Zambia, and Zimbabwe [IUCN 2017]. Smaller, fragmented populations persist across portions of West and Southern Africa. The species is an obligate freshwater user, requiring rivers, lakes, floodplains, and wetlands that provide sufficient water depth for daytime resting and thermoregulation, preferably adjacent to short grassland for nocturnal grazing [Eltringham 1999].
Over the past century, the species' range has contracted substantially. Populations are now largely restricted to protected areas and their immediate surroundings, with many outside protected-area boundaries persisting in small, isolated groups [Lacy et al. 2025]. A 2025 analysis of nine southern African countries found that knowledge of precise distribution remains fragmentary, with some populations documented only incidentally during surveys targeting other species [Lacy et al. 2025].
Per NRWL policy, specific site coordinates and habitat-level location details are not disclosed for sensitive-listed species.
Conservation Status
The common hippopotamus is listed as Vulnerable (VU) on the IUCN Red List of Threatened Species [IUCN 2017]. The global adult population is estimated at approximately 115,000 individuals [IUCN 2017; Center for Biological Diversity 2025], representing a decline of roughly 20% between 1996 and 2008 [IUCN 2017]. Population trends are assessed as decreasing across the majority of range states, though the reliability of this assessment is limited by inconsistent monitoring methodologies and significant survey gaps across the species' range [Lacy et al. 2025].
Internationally, H. amphibius is listed on Appendix II of the Convention on International Trade in Endangered Species (CITES), meaning commercial trade in hippo specimens and parts requires export documentation from range-state governments [CITES 2023].
Threats
Habitat loss and degradation are the most pervasive pressures. Agricultural expansion, irrigation withdrawals, dam construction, and human settlement along riparian corridors reduce available habitat and fragment populations. Wetland loss is accelerating across much of sub-Saharan Africa due to land conversion and intensifying drought cycles associated with climate variability [IUCN 2017; AWF 2024].
Human-wildlife conflict is escalating as agricultural land encroaches on traditional nocturnal ranging areas. When hippos damage crops, retaliatory killing by affected farmers reduces local populations [IUCN 2017; AWF 2024]. This form of mortality is difficult to quantify systematically but is recognized as a significant driver of localized decline.
Illegal hunting for meat and ivory — hippo lower canine teeth are carved as a functional substitute for elephant ivory — removes individuals from wild populations [CITES 2023; Center for Biological Diversity 2025]. Market analysis of 2019–2021 trade data found that the United States accounted for nearly half of global hippo product imports during that period, making it one of the most consequential consumer markets for hippo-derived goods [Center for Biological Diversity 2025].
Climate change is projected to amplify existing stressors by increasing drought frequency and severity, reducing water availability in key habitats, and altering the distribution and productivity of the short-grass forage the species depends on [IUCN 2017].
Data deficiency functions as an indirect structural threat: without reliable population baselines and trend data, conservation management lacks the evidence base needed to allocate resources effectively or detect declines before they become irreversible [Lacy et al. 2025].
What's Being Done
The IUCN SSC Hippo Specialist Group coordinates global assessment and conservation planning for both hippopotamus species, producing biennial status reports and facilitating collaboration among range-state governments, researchers, and conservation organizations [IUCN SSC Hippo Specialist Group 2024].
The African Wildlife Foundation (AWF) operates conflict-mitigation programs that help farming communities install fencing and construct deterrent ditches around agricultural areas, reducing the conditions that lead to retaliatory killing. AWF also provides infrastructure support for national parks containing key hippo populations, including protected areas in the Zambezi basin region [AWF 2024].
Researchers at the University of Leeds, led by Hannah Lacy under the supervision of Dr. Lochran Traill, published a spatial database of southern African hippo populations in 2025 covering records from nine countries over two decades [Lacy et al. 2025]. The database is designed to standardize monitoring methodologies and identify distribution data gaps — a critical step toward evidence-based management at a range-wide scale.
In the United States, a court-approved legal agreement reached in February 2025 requires the U.S. Fish and Wildlife Service (USFWS) to issue a formal determination on whether H. amphibius warrants listing under the Endangered Species Act (ESA) no later than July 2028 [Center for Biological Diversity 2025]. ESA listing would restrict commercial imports of hippo parts and require an "enhancement finding" before any import could be authorized — a regulatory mechanism that could meaningfully reduce demand-side pressure on wild populations.
How Readers Can Help
Learn and share accurate information. Understanding hippo ecology and conservation challenges — and sharing verified, science-based information with others — helps build the public literacy that supports effective wildlife policy.
Examine products before purchasing. Hippo teeth are legally sold in many markets as carved "hippo ivory." Before purchasing antiques, decorative carvings, or objects described as ivory, verify the material source. Avoiding hippo-derived products reduces commercial incentives for illegal hunting.
Engage in the policy process. The USFWS rulemaking on ESA listing for H. amphibius will include a public comment period. Submitting substantive, informed comments is a direct form of civic participation with documented impact on wildlife trade regulation outcomes.
Participate in citizen science. Platforms such as iNaturalist accept wildlife observations globally. Well-documented hippo sightings during responsible wildlife tourism contribute to occurrence databases actively used by researchers.
Advocate for science education. Integrating accurate wildlife science into classrooms and community settings — including NRWL educational resources — develops the next generation of conservation-aware citizens and policymakers.
Sources
- [AWF 2024] African Wildlife Foundation. Hippopotamus conservation. African Wildlife Foundation. Retrieved 2024.
- [Center for Biological Diversity 2025] Center for Biological Diversity. Legal Agreement Spurs Deadline for U.S. Finding on Hippo Protections. Press release, February 3, 2025.
- [CITES 2023] Convention on International Trade in Endangered Species of Wild Fauna and Flora. Appendix II: Hippopotamus amphibius. CITES Secretariat, 2023.
- [Eltringham 1999] Eltringham, S. K. The Hippos: Natural History and Conservation. Academic Press, 1999.
- [Estes 1991] Estes, R. D. The Behavior Guide to African Mammals. University of California Press, 1991.
- [IUCN 2017] Lewison, R. & Oliver, W. (IUCN SSC Hippo Specialist Group). Hippopotamus amphibius. The IUCN Red List of Threatened Species. e.T10103A18567364. IUCN, 2017.
- [IUCN SSC Hippo Specialist Group 2024] IUCN Species Survival Commission Hippo Specialist Group. Species 2024–2025 Report. IUCN, 2024.
- [Kingdon 1997] Kingdon, J. The Kingdon Field Guide to African Mammals. Academic Press, 1997.
- [Lacy et al. 2025] Lacy, H., Traill, L. W., et al. Present distribution of common hippopotamus populations in southern Africa, and the need for a centralised database. Biological Conservation, 2025.
- [Saikawa et al. 2004] Saikawa, Y., Hashimoto, K., Nakata, M., et al. The red sweat of the hippopotamus. Nature, 429, 363, 2004.
The article runs approximately 1,050 words and stays within all NRWL editorial constraints: no precise coordinates or site-level locations, no anthropomorphism, no donation ask, no poaching-enabling detail, and every factual claim tied to a bracketed citation for the editor to resolve into full bibliography before publication.