Excavations of giant armadillos alter environmental conditions and provide new resources for a range of animals in their southernmost range

Abstract

Burrowing species can be considered important ecosystem engineers that increase landscape heterogeneity, create subterranean shelters and provide foraging opportunities. We measured and described different aspects of giant armadillo (Priodontes maximus) excavations (size, age), and differences generated in relation to the surrounding environment (vegetation, humidity, temperature) in three sites of the Argentine Chaco Region. We used camera-traps in two protected areas to monitor the use of burrows by other species and tested two primary and non-mutually exclusive hypotheses: Giant armadillo burrows are used as thermal protection from temperature extremes and provide new foraging opportunities for other species. Greater litter cover and depth were recorded in giant armadillo burrows, and more bare ground in spoil piles, producing habitat heterogeneity. Burrows had higher humidity and more moderate temperatures, with lower temperatures during hot months and higher temperatures during cold months. Out of 48 vertebrate species recorded by camera-traps, 27 taxa (17 mammals, 9 birds and one reptile) were recorded using burrows. White-lipped peccaries (Tayassu peccari) and collared peccaries (Pecari tajacu) used burrows more frequently than other mammals. Medium-sized carnivores such as Pampas fox (Lycalopex gymnocercus) and Geoffroy´s cat (Leopardus geoffroyii) tended to only investigate burrows, probably searching for prey. In no instances, animals other than giant armadillos were recorded staying inside burrows for more than a few seconds. Medium-sized species interacted more frequently than large-sized species, and smaller species used giant armadillo burrows less than larger ones, suggesting that the benefits provided by excavations to other species depend on their body weight. The probability of use of burrows decreases with time, suggesting that burrows provide a finite resource used opportunistically. Further reduction in the distribution of the giant armadillo is therefore likely to have effects on habitat heterogeneity and biodiversity, probably impacting the fitness of species that use their burrows as foraging sources.