• dry tropical forest;
  • Formicidae;
  • neotropical ant guilds;
  • open-pit coal mine

Open-pit coal mining causes strong negative impacts on biodiversity because this activity completely removes thick layers of soil. Focusing on ants as functional agents responding to mine site rehabilitation has proven useful in improving restoration practices. This study sought to evaluate the success of the 20-year-old ecological rehabilitation program at El Cerrejón, one of the world's largest open-pit coal mining operation located in a vulnerable dry tropical forest region of Colombia. This study compared ant assemblages in 13 sites classified along a gradient of rehabilitation sites aged 0–14 years, as well as in three forest reference areas. Two sampling methods (pitfall traps and visual search) were conducted during three sampling periods. Seed removal by ants was also quantified at seven of the 13 sites using seed bait from native plants. Eighty-two ant species, belonging to 29 genera, were found. The highest number of ant species were found inside the forests. Ant species richness increased with rehabilitation age of sites, along with higher canopy cover and milder soil temperature. Rehabilitation actions enhancing these ecological factors might, therefore, favor the presence of wild fauna such as ants. The oldest area (14 years) was the most similar to the forests, both in terms of functional ant groups (guilds) and dominant species. Seed movement was highest in the 14-year-old restored area and was similar to that of the forests, suggesting that this ecological function has been partially restored and that the movement of seed dispersal agents across the landscape would be enhanced.