Giant panda (Ailuropoda melanoleuca) bleats signal the caller’s identity at distances of up to 20 metres and their sex at distances of up to 10 metres, according to a study in Scientific Reports. Cues about the identity and sex of the caller contained in bleats may provide important information for pandas interacting at close range in dense bamboo thickets where there is limited opportunity for visual contact.

Giant pandas are solitary animals. Therefore, effective communication is likely to be crucial for locating mates and avoiding potentially aggressive competitors. Male giant pandas are known to bleat at high rates when they encounter females on heat, suggesting that these calls are important for coordinating mating activities. However, the information disclosed in bleats cannot be useful to giant pandas unless it is reliably transmitted in the bamboo forest environment they live in.

Benjamin Charlton and colleagues played back 100 bleats (10 from each of 10 adult giant pandas) and re-recorded them at distances of 10, 20, 30 and 40 metres from the playback speaker. The playback and re-recordings were carried out in a mixed bamboo plantation at San Diego Zoo Safari Park, California, where the bamboo density is similar to that in natural panda habitats. The results show that the acoustic structure of giant panda bleats remains distinctive over distances of up to 20 metres in a bamboo forest environment, but that giant pandas would be unable to use bleats to tell males and females apart over distances greater than 10 metres.

By identifying the likely range over which bleats relating to mating are distinguishable to pandas, the study sheds new light on giant panda reproductive strategies.