Ultrasonic alarm call of Mongolian gerbils (Meriones ungiuculatus) in the wild and in captivity: a potential tool for detecting inhabited colonies during population depression

In this study, we describe the acoustic structure of ultrasonic alarm calls of Mongolian gerbils Meriones unguiculatus in the wild and verify these calls as belonging to Mongolian gerbils by comparison of their acoustic parameters with alarm calls recorded in captivity. Both in captivity and in the wild, the alarm calls of Mongolian gerbils represented prolonged calls with an average duration of 118 ms and a flat contour and an average maximum fundamental frequency of 26.84 kHz. We found that alarm calls of captive Mongolian gerbils were shorter and higher in fundamental frequency and followed in a quicker succession than in the wild. Although the dataset size is not sufficient to determine significant acoustic variation between the populations, we discuss the potential reasons of the acoustic differences between the ultrasonic alarm calls produced in the wild and in captivity in our study and between the alarm calls reported in literature for different captive populations. We propose a method for non-invasive estimation of occupancy of the burrows by Mongolian gerbils in fragmented colonies at very low population density, by presence of the ultrasonic alarm calls.