Climate fluctuations as a cause of rarity in fairy armadillos

Despite having a moderately large distributional area, both the pink fairy armadillo (Chlamyphorus truncatus) and particularly the Chacoan fairy armadillo (Calyptophractus retusus), which are among the least known xenarthrans, appear to be rare or patchily distributed. Although low density in species with large range sizes has been associated with large body size, this is not the case for fairy armadillos. We propose that past climate variations may have caused their current low densities, and evaluate retractions and expansions of suitable areas of fairy armadillos by extrapolating the consensus of habitat suitability models fitted with current climatic conditions to past conditions. We found great variation in suitable area along time in both species, with a drastic reduction in the Last Interglacial (LIG) period when compared with current situation. Both the variations and the reduction during LIG were more pronounced in Calyptophractus than in Chlamyphorus. We postulate that past extreme reductions in suitable areas could cause a delay in the recovery of the populations, resulting in low densities despite climatic conditions during more benign times allowing a more widespread distribution.