A Blind-Test Comparison of the Reliability of Using External Morphology and Echolocation-Call Structure to Differentiate Between the Little Brown Bat (Myotis lucifugus) and Yuma Myotis (Myotis yumanensis)

Abstract

Abstract Species that overlap in their morphologies are sometimes difficult to distinguish from one another, which can complicate species’ conservation and management. The Little Brown Bat (Myotis lucifugus) and Yuma Myotis (Myotis yumanensis) are sympatric in parts of their range in western North America, and they overlap in morphology, making them difficult to tell apart in the hand in some areas, such as the Pacific Northwest. We compared various methods of distinguishing between M. lucifugus and M. yumanensis to genetic results, using a blind test approach to remove observer bias. Using multiple independent observers, we used external morphology and echolocation-call structure to classify bats from a maternity colony consisting of both species. Genetic analysis confirmed 13 M. lucifugus and 40 M. yumanensis. Minimum echolocation-call frequency separated 100% of M. lucifugus from M. yumanensis using a cut-off of 43 kHz. All M. lucifugus had a minimum echolocation-call frequency ≤42.8 kHz, whereas M. yu...