Alarm call responsivity of mallard ducklings: II. Perceptual specificity along an acoustical dimension affecting...

Mallard ducklings (Anas platyrhynchos) inhibit their vocal and locomotor behavior upon hearing the maternal alarm call. An important acoustic feature of the call that affects such inhibition is the slow repetition rate of the notes. This study assesses the range of repetition rates that affect behavioral inhibition in 1-day-old domestic mallard (Peking) ducklings. Four hundred and fifty maternally naive ducklings were tested in groups of 30 to repetition rates ranging from .2 to 3.0 notes/sec in 2/10-sec increments. Various behavioral measures (i.e., incidence of inhibition, latency and duration of inhibition) revealed that the optimal range of repetition rates affecting inhibition extends from .8 to 1.8 notes/sec. Within this range, 1.0 and 1.6 notes/sec are particularly effective. The efficacy of these particular 2 rates may reflect their correspondence with the rates of the modal alarm call and certain kinds of self-produced embryonic vocalizations, respectively. Unexpectedly, very slow repetition rates (.2 and .4 notes/sec) are not as effective as faster rates in promoting inhibition. Thus, the inhibitory response exhibited by ducklings upon hearing the alarm call reflects auditory perceptual specificity to a range of moderately slow repetition rates that are characteristic of normally occurring sounds of the perinatal environment.