Biogeography of body size in the common vampire bat (Desmodus rotundus, Chiroptera) in Colombia

Biogeography can illuminate spatial patterns of intraspecific morphological variation along environmental gradients. We evaluated whether body size in the common vampire bat (Desmodus rotundus) varies with climate and elevation across Colombia using 1076 museum and field specimens (1921-2023). Field specimens originated from diverse environmental conditions, including sites with mean annual temperatures ranging from 8.94 to 28.94 °C, annual precipitations from 515 to 7132 mm, and elevations from 4.6 to 3476 m a.s.l. Forearm length, a proxy for body size, was analysed with regression models, including Colombian department as a random effect. Linear models showed that forearm length decreased with mean annual temperature (females: R ² = .023, β = -.143, P = .006; males: R ² = .044, β = -.173, P = 1.03 × 10^-5) and increased with elevation (females: R ² = .038, β = .001, P = 3.66 × 10^-4; males: R ² = .039, β = .001, P = 3.35 × 10^-5), with an overall decrease of .19 mm per 1°C across all individuals. In contrast, linear mixed-effects models found no significant effects of temperature, elevation, precipitation, or latitude. These contrasting results suggest data limitations and that patterns detected by simpler models disappear when accounting for the spatial structure of the sampling. We argue that temperature is not a robust predictor of body size in D. rotundus. Our findings advance the biogeography of D. rotundus and provide a foundation for the uncertainty of climate change effects on bat morphology.