Acoustic properties of male advertisement and their impact on female responsiveness in little penguins Eudyptula minor

We examined the relationship between acoustic properties of male advertising calls, male body size and female responses in little penguins Eudyptula minor . Larger males produced calls of lower frequency. Playback experiments indicated that females were more likely to respond to low or medium pitched calls, than to high ones (although only 28% of females responded vocally to playback). This may reflect the interest of unmated females in large to medium sized senders as potential mates, or indicate a stronger territorial response to large intruders.