The information content of giant panda, Ailuropoda melanoleuca, bleats: acoustic cues to sex, age and size

The acoustic structure of mammal vocalizations often encodes information on different phenotypic traits of the caller that is potentially available to receivers. Here we used a source–filter theory approach to investigate, in light of their biophysical modes of production, which acoustic features of male and female giant panda bleats have the potential to convey information on the caller's sex, age and body size. Our results revealed that both source- and filter-related acoustic features of giant panda bleats provided reliable information on a caller's sex, age and body size. However, when we considered both sexes separately we found that male and female giant panda bleats differed in their potential to signal information on the caller's age and body size: only male bleats contained reliable information on the caller's body size while female bleats were more predictive of the caller's age. We go on to discuss the anatomical basis for our findings, consider the potential functional relevance of signalling this type of information in giant panda sexual communication, and suggest future empirical investigations that should better enable us to understand this species' mating behaviour.