Morphometric and bio-acoustic profiling of Myotis aurascens (Chiroptera, Vespertilionidae) in east Asia: documenting range extension in China and elevational distribution

During a Chiroptera resource survey conducted in 2023 on the Pamir Plateau of China's Xinjiang Uygur Autonomous Region, two male bat specimens were captured. External morphology examination revealed small-sized individuals characterized by long, narrow ears with straight tragus structures tapering to sharp tips—features diagnostic of the genus Myotis . Echolocation call parameters were as follow: omitted signals exhibited a start frequency of 65.12 ± 2.12 kHz, end frequency of 42.78 ± 1.27 kHz, peak energy frequency of 47.41 ± 1.46 kHz, pulse duration of 2.52 ± 0.26 ms, and inter-pulse interval of 94.01 ± 31.41 ms. Integrated analyses incorporating mitochondrial cytochrome b (Cytb) gene sequencing, (skull) morphological traits, and bio-acoustic data conclusively identified the specimens as the steppe whiskered bat, Myotis aurascens . This discovery constitutes the first documented occurrence of M. aurascens in Xinjiang, thereby expanding the confirmed distribution range of this species in China. Notably, these specimens represent the highest-altitude record for the species at 3,200 m above sea level. Our study provides the inaugural comprehensive description of cranial morphology and echolocation signatures for this species in high-altitude habitats. These findings significantly enhance regional biodiversity inventories and contribute critical baseline data for plateau ecosystem research.