The definitive answer to whether hippos exist in South America is yes, but they are not native. An established population of hippopotamuses in Colombia represents the world’s largest invasive megafauna species. Their presence is a direct result of human action, creating a complex environmental problem with profound implications for local ecology and management.
The Origins of Colombia’s Wild Hippos
The unexpected presence of hippos in Colombia traces back to the private menagerie of notorious drug trafficker Pablo Escobar. In the late 1970s or early 1980s, Escobar illegally imported four hippopotamuses—one male and three females—for his sprawling estate, Hacienda Nápoles. This ranch, located about 100 kilometers east of Medellín, served as his personal zoo, housing various exotic animals from around the world.
Following Escobar’s death in a 1993 shootout, the government seized the estate, and most of the exotic animals were relocated to legitimate zoos. However, the hippos were abandoned on the unattended property due to the immense logistical challenge and cost of transporting such large, aggressive animals. The four initial animals were left to roam the artificial lakes and surrounding wetlands, where they quickly adapted to the favorable tropical conditions.
Current Population and Geographic Range
The founder population of four hippos began reproducing successfully, unchecked by the natural predators, diseases, or droughts that regulate their numbers in Africa. This lack of environmental constraints has led to a rapid population growth rate, estimated to be between 9.6% and 14.5% per year. This rate is significantly higher than the reproductive rate observed in their native African habitat.
Scientists estimate the population has grown to between 181 and 215 individuals as of 2023, though precise tracking is difficult. The hippos have spread beyond Hacienda Nápoles, moving across the Magdalena River basin, Colombia’s most important river system. Their range now extends hundreds of kilometers from the original estate, making containment nearly impossible. Population models predict that if the current growth rate continues without intervention, the number of hippos will exceed 1,000 by 2050.
Ecosystem Changes Caused by the Invasion
The hippos’ size and behavior are causing significant disruptions to local aquatic ecosystems, classifying them as “ecosystem engineers.” They spend their days submerged in water and graze on land at night, a process that moves massive amounts of terrestrial organic matter into the waterways. This transfer occurs through defecation, with a single hippo producing up to 13 pounds of waste daily.
The introduction of this waste material leads to eutrophication, or nutrient loading, which drastically alters the water chemistry. The excess nutrients, particularly carbon and nitrogen, fuel rapid growth of algae. When the algae die and decompose, they consume large amounts of dissolved oxygen. This creates hypoxic conditions, or “dead zones,” which are detrimental to native fish and other aquatic species and can lead to mass fish kills.
The hippos’ constant wallowing physically alters the riverbanks, causing soil erosion and changing the hydrological structure of the wetlands. Their presence introduces competition for resources with native megafauna, such as the endangered manatee and the capybara, displacing them from feeding and resting areas. Wild hippos can also carry pathogens like Brucella and Leptospira, posing a risk of disease transmission to local wildlife, livestock, and humans.
Legal Classification and Management Strategies
The ecological crisis prompted the Colombian government to take formal action concerning the non-native species. In March 2022, the hippos were officially declared an invasive species by the Ministry of Environment and Sustainable Development. This legal classification provides the framework for implementing control strategies aimed at reducing their numbers and mitigating environmental impact.
Management efforts are complicated by public sentiment and the high cost of intervention, especially since a judicial ruling banned culling after a hippo killing in 2009. Current strategies focus on fertility control, including surgical sterilization and the use of the chemical contraceptive GonaCon. These methods are expensive, logistically challenging, and slow to have a widespread effect, with sterilization costing tens of thousands of dollars per animal.
The government is exploring translocating hippos to international sanctuaries in countries like India and Mexico, but this process is costly and requires specialized facilities. Without a rapid and effective management plan, the population is projected to continue its exponential growth, narrowing the window for cost-effective control.