A hippo in the room: Predicting the persistence and dispersion of an invasive mega-vertebrate in Colombia, South America

Abstract

Biological invasions are a big concern due to their potential to impact ecosystems, as well as local people. The hippo Hippopotamus amphibius, native to Africa, has invaded extensive areas of the Magdalena River basin (Colombia) over the past decades, and has been considered the largest invasive animal in the world. Here, we propose the use of two approaches of predictive modeling, in order to guide recommendations for the management of this biological invasion. First, we developed a population viability analysis (PVA) to simulate a hypothetical population growth under different management scenarios. Next, we explored the potential invasion area under future climate change scenarios throughout ecological niche modeling analyses. PVA models predicted that in the absence of an intense culling/hunting pressure, the population size will continue to steadily increase, which is consistent with the population growth observed during the last 20 years. Furthermore, our static and dynamic habitat suitability projections suggested that without dispersal limiting factors, potential colonization habitat for hippos may become very extensive across the landscape and can be favored by climate change in the future. Therefore, our findings show the urgent need of taking critical management decisions by the Colombian authorities, which should be focused on limiting the hippos' population growth and expansion. Ignoring cost-benefit considerations for the control of this invasive species may have unexpected and long-term social and ecological implications. However, the proposal of a course of action can become controversial when the species has a charismatic value for the society, regardless of its ecological or social impact.