Poster Presentation Society for Freshwater Science 2025 Annual Meeting

Hungry, Hungry Snails: Importance of Hippo Dung in the Mara River, Kenya (118841)

Kevin Fuentes-Gonzalez 1 , Anna Reside 2 , Yimei Du 1 , Abigail McGuire 1 , Amanda Subalusky 3 , Christopher Dutton 3 , Emma Rosi 4 , David Post 5 , Therese Frauendorf 1
  1. Biology, Colgate University, Hamilton, New York, United States
  2. Biological Sciences, Idaho State University, Pocatello, Idaho, United States
  3. Biology, University of Florida, Gainesville, Florida, United States
  4. Cary Institute of Ecosystem Studies, Millbrook, New York, United States
  5. Ecology and Evolutionary Biology, Yale University, New Haven, Connecticut, United States

Hippopotami play an important role in the Mara River ecosystem, where they spend most of their lives in the water, adding high amounts of dung into the river. Previous research showed that aquatic invertebrate diversity and abundance benefit from hippo dung. With current hippo population declining, we want to understand why hippo dung is important to invertebrates and if the amount of hippo dung matters. Twenty experimental streams contained one of three types of hippo dung: blended dung (to determine if dung was an important food source for invertebrates), boiled dung (to determine if hippo dung was structurally important for invertebrates), or unprocessed dung (food and structure). The amount of dung in each stream ranged from 0g to 240g for each dung type. These amounts reflected concentrations observed in the Mara River, except the 240g concentration. This high concentration of dung helped us determine if overloading of dung can be a problem. After 3 weeks, invertebrates were collected from each stream and we identified, counted, and measured them. Across treatments, the abundance of invertebrates increased as the amount of dung increased. However, concentrations of hippo dung higher than what has been documented in the Mara River showed declines in invertebrate abundance. Snails (Physidae & Planorbidae), which are algal grazers, had the highest abundance in all samples across all treatments. Finally, our results showed that hippo dung is important not only as a food source but also as a habitat, providing safety against abiotic (flooding) and biotic (predators) factors.