Unusual use of two types of alarm call by the long-tailed ground squirrel (Spermophilus undulatus, Rodentia, Sciuridae)
Alarm call of long-tailed ground squirrel (Spermophilus undulatus (Pallas 1778)) was tape recorded in the field and its time-frequency characteristics were analyzed. It is known there are two types of signal, the first one is a short (0.05-0.08 s) broad frequency chat while another is a longer (0.13 s) descending narrow frequency whistle. Previously, it was thought that two signals are discrete and reflect the nature of hazard: broad frequency chat is given upon the approach of a ground predator and narrow frequency whistle is given upon the approach of an aerial predator (Nikolski, Wallschlager, 1982). Further observations showed that both types of signal could be issued upon both ground and aerial predators. Stimuli that cause applying of some type of signal remains unclear.