Aliens on the menu: high prevalence of introduced ants in the diet of Galápagos lava lizards, Microlophus spp.

The Galápagos Archipelago, a unique and ever-changing natural experiment, has seen an increase in introduced species due to increased human mobility. Among these, introduced ants represent a significant concern given their potential to reach high densities and displace native fauna. This study analyzed the diet of six Galápagos lava lizard species (Microlophus spp.) through the examination of 177 fecal pellets collected over two seasons. We identified 7084 food items across 39 categories, with ants predominating, making up 65% of occurrences and 90% of the total abundance. Notably, introduced ants constituted 57.1% of these occurrences and 79.4% of the total abundance, indicating a significant prevalence of introduced prey. This finding suggests a substantial shift in the islands’ ecological dynamics away from their natural state (i.e., without introduced ants). We also explore the dietary breadth of each lizard species and their similarity. Finally, we discuss the possible direct and indirect effects of the high prevalence of ants in the diet of Galápagos lava lizards, report interesting findings in their diet, and advocate for the use of feces as a non-invasive method to monitor for invasive ants. Our study highlights the ecological changes underway on these islands, underscoring the need for targeted conservation strategies to mitigate the impact of invasive species and preserve Galápagos biodiversity.