Fig. 4. Hearing thresholds (mean ± S.D.) of five species of Neoconocephalus relative to the highest sensitivity. Absolute sensitivity at this point ranged between 27.5 dB SPL and 31.8 dB SPL. The peak frequency (vertical lines) and the -3 dB band (horizontal lines) of the low-frequency component of the calls are indicated by vertical lines. N. robustus, N=14 in nine animals; N. bivocatus, N=19 in 11 animals; N. nebrascensis, N=18 in 12 animals; N. ensiger, N=12 in seven animals; N. retusus, N=19 in 10 animals.