Duet structure provides information about pair identity in the red-crowned crane (Grus japonensis)

We studied the acoustic features of the endangered red-crowned crane (Grus japonensis), and, specifically, whether or not the duets carry information about a mating pair identity. The population of this species in the wild is only approximately 2,000 individuals. In 2003–2006, we recorded 343 duets from eight captive and two wild pairs. All of the duets contained an introduction, an unordered alternation of pair mate calls, followed by the main part, representing the regular sequence of syllables, containing 1–2 male and 1–4 female calls per syllable. We subdivided the syllables into five types, by the number of male and female calls per syllable, and analyzed the occurrence of the different syllable types in the duets of the ten pairs. The analysis showed the sustainable pair-specific use of particular syllable types through the years. The discriminant analysis standard procedure, based on seven frequency and temporal parameters of male and female calls, showed 97.7% correct assignment to the pair, which is significantly higher than random values. The high pair specificity of the duet acoustic structures provides the basis for call-based censuses. This would enable the monitoring of the red-crowned crane mating pairs in their natural habitat.