Hippos in South America? It’s More Likely Than You Think
By Darcy LaCosse
Colombia has a huge invasive species problem: literally. The Magdalena River has become home to a growing population of hippopotamuses, and ecologists are worried about the effect this non-native species will have on the important river habitat.
Hippo 101
Hippopotamus amphibius, or the common hippo, is one of the world’s largest land animals by mass. They are native to Africa, where they spend their days relaxing in the water or wallowing in the mud to stay cool and lumbering ashore to feed on grasses after the sun sets. Hippos live in a variety of habitats, only requiring the availability of enough water to submerge in and grasses to eat. As ecosystem engineers, their dung provides valuable nutrients to the aquatic environments. Lions and Nile crocodiles often prey on baby hippo calves, but can rarely take down a full-grown adult, since hippos are quite aggressive. This aggression also manifests in conflicts with African people: hippos kill an average of 500 people per year, making them one of the most dangerous animals on Earth.
How in The World Did They Get to Colombia?
In the late 1970’s, Colombian drug lord Pablo Escobar purchased four hippos from New Orleans for his mansion’s private zoo. Upon his death in 1993, most of the animals were relocated to various zoos. However, the hippos were deemed too difficult to move and were simply left on the estate. Fast forward to the late 2000’s and this small population had increased to 16–27 hippos, many of whom had escaped the estate and were being sighted up to 55 miles away in the Magdalena wetlands. At this point, the Colombian government instated a culling plan, but after a picture of a dead hippo went viral, backlash from animal rights groups put the hippos under protection. The government then shifted strategies to sterilization: capturing hippos and giving them a contraceptive to stop their ability to reproduce. Fast forward to the present, and the current population is estimated to be around 100, demonstrating the insignificant impact the sterilization is having, which in addition is very expensive. Recently in 2020, a farmer was chased and injured by a hippo, prompting investigations into the population’s expected growth.
Modeling the Hippos: Here’s What Scientists Have Found
In order to look into the expected population growth and invasive potential, a team of scientists created a series of models to predict how the hippo population might change over the next several decades. First, the team modeled the population growth under a variety of scenarios, including differing rates of sterilization as well as extraction (either relocating or killing the hippos). In addition, the team also used climate models to simulate the possible changes in the Colombian environment due to climate change, and how these changes could affect the amount of area the hippos could spread to.
They found that without any management, the hippo population will undergo exponential growth before plateauing in 2039 with around 1400 hippos. In addition, almost all of their simulated scenarios for both the sterilization and the extraction strategies showed the same exponential growth and plateau — most methods just delayed the time the 1400 hippo plateau was expected to occur. Regarding the hippo’s invasive potential, the team’s climate simulations showed that in the coming decades, climate change will likely alter the surrounding habitats of the Magdalenian wetlands in a way that is hippo-friendly, which will probably allow the hippos to expand their range into a much broader area. Using the single scenario where numbers decreased, the team recommended extraction of 30 hippos per year, which would deplete the entire population by 2033.
Implications for Colombian Ecosystems
Despite their invasive label, many have advocated for the hippos to be left to flourish in the Magdalenian wetlands. Hippos are quite a charismatic species, and locals have gotten quite attached to the big guys. Arguments for letting the hippos stay range from ecotourism potential for disadvantaged people to claims that the hippos are filling an available niche in the ecosystem for aquatic mammals. However, the scientific team’s paper argues that the costs far outweigh the benefits of keeping the hippos around.
The habitat that the hippos occupy in Colombia is similar to their native African with one glaring exception: the Magdalenian wetlands experience far less drought than African habitats. Along with predation, drought help keep the hippo population within reasonable numbers. But because the Colombian equivalents of African predators (jaguars and caimans/crocodiles) are not preying on them, the only thing limiting the growth and expansion of the hippos is the availability of high-quality habitat… Which is literally all around them and projected to spread even farther according to the team’s models. This means that the hippos have the potential to spread across the ecosystem rapidly, which could spell disaster for the native species that live there. Some species of concern are the endangered Antillean manatee and two turtle species, the latter of which are critically endangered and mostly restricted to the Magdalenian wetlands. The fast colonization could change the physical and chemical standard of the wetlands too fast for native species to adapt and threaten or endanger native fish and plants.
There is also a concern for the people in the area. Many of them are disadvantaged and depend on the river for their livelihood. For example, if fish decline, this could pose a significant threat to a source of food and income for these people. Hippos can also be attracted to crop fields, eating and/or trampling farmers’ hard work. And hippos are dangerous — one of the world’s deadliest animals. Luckily, no one has been killed yet, but incidents like the one in 2020 show that it is only a matter of time.
In Conclusion
The paper recommends that Colombia takes decisive action against the hippos and demonstrates the possible consequences of failing to do so. We should heed this warning, and work to extract these hippos before it’s too late.
Works Cited
Castelblanco-Martínez, D. N. et. al. (2021). A hippo in the room: Predicting the persistence and dispersion of an invasive mega-vertebrate in Colombia, South America. Biological Conservation, 108923. Retrieved January 26 2022 from https://www.sciencedirect.com/science/article/pii/S0006320720309812?casa_token=oH6nUubG7bUAAAAA:yiAttOzlzFzs1cCK8EOqNqcR1jzw_vQ25MMsEK4eLPGYnrTdW0hAX01eJ1qMAX2FAPKKs2OS#bb0235
Edwards, J. (2021, October 18). Drug lord Pablo Escobar smuggled hippos into Colombia. Officials are now sterilizing the invasive species. The Washington Post. Retrieved January 26 2022 from https://www.washingtonpost.com/nation/2021/10/18/pablo-escobar-colombian-hippos-sterilization/
Nagvekar, R. (2017, March 8). Zoo gone wild: After Escobar, Colombia faces his hippos. The Politic. Retrieved January 26 2022 from https://thepolitic.org/zoo-gone-wild-after-escobar-colombia-faces-his-hippos/
