Predicted range expansion of Desert Mule Deer under future climate scenarios

The desert mule deer (Odocoileus hemionus crooki) is distributed throughout the southern United States and northern Mexico. As a large herbivore, this subspecies plays a crucial role in maintaining ecological balance. While its distribution is closely linked to water availability and vegetation type, climate change is increasingly altering these factors and shifting potential habitats. This study aimed to model the current potential distribution of O. h. crooki and predict distribution changes for the 2021–2040 period in relation to bioclimatic factors. Presence data were compiled from multiple sources, including GBIF, nocturnal sightings, pellet counts, and camera traps. These records were correlated with 19 bioclimatic variables from WorldClim. We utilized 164 presence points, partitioned into 50% (82 points) for model training and 50% for testing. Ecological niche modeling was performed using the kuenm R package, which provides a robust framework for MaxEnt development. Among the selected variables, BIO 9 (mean temperature of the driest quarter) exhibited the highest contribution to the model, given its high permutation value. Under the future climate scenario of extreme warming (BCC-CSM2-MR model, SSP5-8.5 scenario), the potential distribution of the desert mule deer is predicted to increase by 48.51% in the United States and 45.52% in Mexico. However, actual expansion into these newly suitable areas will likely be constrained by human-dimension factors overlooked by macroclimatic models, including transboundary border infrastructure, urban growth, and novel competitive interactions, emphasizing the need to integrate bioclimatic forecasts with regional land-use and adaptation policies.