Response of endemic lizard populations to attempted eradication of invasive predators on a Galápagos island

Invasive mammalian predators are principal drivers of biodiversity loss on islands, and eradications are a powerful tool to address this threat. However, the demographic responses of ecologically important reptiles to such interventions remain poorly quantified, despite reptiles regularly functioning as key prey and seed dispersers in island ecosystems.

We conducted a 5‐year Before–After study on Floreana Island, Galápagos, to evaluate changes in the abundance of endemic lava lizards ( Microlophus grayii ) and geckos ( Phyllodactylus spp.) following a multi‐species eradication attempt. Lizard transect surveys were performed for 3 years before and 2 years after toxicant application, with additional monitoring at three untreated control islands.

Following treatment, detections of feral cats ( Felis catus ) and rats ( Rattus rattus ) ceased in survey areas, while mice ( Mus musculus ) remained and likely increased in later months. In less than 2 years post‐treatment, gecko relative abundance tripled and lava lizard relative abundance increased eight‐fold, whereas no increases were observed on the control islands.

Habitat suitability based on surrounding vegetation and ground cover emerged as a strong independent predictor of lizard abundance, highlighting the importance of accounting for habitat heterogeneity when interpreting population responses to eradication. Our findings provide the first empirical evidence of small lizard recovery in the Galápagos following an invasive predator eradication attempt and demonstrate that responses can be rapid when predation and competition pressure are reduced.

Synthesis and applications Integrating reptile monitoring into invasive predator eradication programmes can reveal rapid responses in ecologically important, yet frequently overlooked, components of island ecosystems. Accounting for habitat variation alongside changes in predator communities will improve interpretation of post‐eradication population responses and inform subsequent restoration actions, including native species reintroductions. More broadly, understanding how reptile populations respond to predator removal can help anticipate changes in trophic interactions and ecosystem processes as island restoration progresses.