EFFECTS OF INTERINDIVIDUAL VARIATION IN ECHOLOCATION CALLS ON IDENTIFICATION OF BIG BROWN AND SILVER-HAIRED BATS

Identifying bat species from their calls is a common technique in stud ies of habitat use. I tested the hypotheses that significant interindi vidual intraspecific variation exists in the echolocation calls of bat s as detected by frequency-divide ultrasonic detectors, and that such variation could greatly affect die accuracy of species identification. I restricted analysis to 2 species that have similar but reportedly d istinguishable calls. There was significant intraspecific variation in 6 variables for each species, and frequency distributions of the 2 sp ecies overlapped greatly for all 6 variables; hence, univariate analys is was ineffective at differentiating between species. The best of 4 e xperienced human observers correctly identified the species for only 7 0% of 47 call sequences compared to >95% correct classification by dis criminant function analysis. Alterations in current methodology can im prove accuracy of identification and thus the value of habitat studies and manage ment decisions that rely on such identification.