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Biology major Joe Coolidge ’24, from Hamilton, N.Y., describes his summer research into the effects of hippo dung on invertebrate species in sub-Saharan Africa.

This summer, I worked in the lab of Assistant Professor of Biology Therese Frauendorf, researching the effects of hippo dung on invertebrate species in the Mara River in sub-Saharan Africa.

Invertebrates are ecologically important in river ecosystems globally, and the Mara River is a crucial water source in East Africa. Little is known about food-web dynamics in this river. Hippos spend a lot of time in the Mara River, and we want to understand their dung’s role in the river food web as a significant nutrient input. I am interested in understanding hippos’ impact on their habitat to guide conservation efforts for these animals.

For the first portion of this project, I extracted microscopic invertebrates from samples that were collected from experimental streams at the University of Florida. The experiment tested whether invertebrate species use hippo dung as food, shelter, or both. I removed more than 4,000 invertebrates from hippo dung that was either blended (food only), boiled (shelter only), or left untreated (both) and measured their biomass. From this, I can learn why hippo dung is important for river invertebrate communities.

For the second portion of this project, I am using ImageJ software to analyze photos of the gut contents of invertebrates collected from the Mara River. Invertebrates were sampled during the dry and wet seasons from different sites of the river along a gradient of hippo dung input. I have measured and identified over 100 food particles from each invertebrate so far, to see how the diet of different invertebrate species changes with the seasons and the level of hippo activity.

So far, I have found that seasonal changes have different effects on specific groups of invertebrate species. In particular, as I continue with this portion of the project, I hope to learn how the inputs of hippo dung interact with seasonal changes to influence the diet of these same invertebrate species groups.

After this summer, I hope to continue with research in ecology. I love learning about the complex systems through which life thrives on Earth, and I want to use research to support environmental protection. Along with the knowledge I have gleaned from my experience this summer, I have gained several new research skills from collecting data to presenting results. This summer experience has bolstered my interest in ecological research and set me up for future success in a research career.