Figure 4 From: Knee-clicks and visual traits indicate fighting ability in eland antelopes: multiple messages and back-up signals Narrow-band spectrograms (window length = 0.03 s, band width = 43 Hz, Gaussian window shape) of knee-clicks from the same bull recorded in two consecutive years. Note the drop in knee-click frequency between years compared with the constancy over the short term.Back to article page