The adaptive function of the cheetah’s contact chirp

We will study how cheetahs communicate, with focusing on their chirping sounds. This call is exceptionally high for an animal the size of a cheetah and amazingly alike the sound of a little bird. The chirp is used to keep contact between affiliated individuals, like male coalitions or between a mother and her cubs. The chirp is intriguing for two reasons: (1) it contradicts the "acoustic allometric hypothesis," which states that big animals emit lower-frequency sounds than small animals, and (2) it is unusual for an animal living in an open habitat to employ a high-pitched sound as a contact call. The auditory adaptation hypothesis states that low frequencies and longer call durations are better for transmitting sounds across long distances. However, the cheetah`s evolution has been influenced considerably by mortality due to competitive predation by, for example, lions. We intend to investigate the hypothesis that the high-pitched bird-like call is a type of auditory crypsis used as a defense strategy against eavesdropping competitors and/or to escape detection by prey. We specifically aim for the following goals: (1) explore the information communicated in cheetah contact chirps, (2) determine how far these calls propagate in the savanna, and (3) determine if competitors such as lions and prey species such as antelopes detect and discriminate cheetah chirps. We will conduct acoustic analysis of chirps from individuals of various ages and sexes, as well as playback experiments, to see how lions and ungulate species react to cheetah chirps in comparison to other cheetah calls, calls of competitors or predators (such as lions, hyenas, or wild dogs), and bird calls. By undertaking this research, we will learn more about the evolutionary pressures that determine how animals employ sound to communicate. Acoustic crypsis is an intriguing phenomenon that is likely one of the least researched surviving strategies, particularly in mammals. It might open the way for further research on other organisms that live in comparable environments (such as mammals that are both predators and prey), where similar adaptations may have been dismissed previously. By providing the framework for a new theory about how the frequency of an animal`s call changes as it adjusts to its environment, we will begin to fill a long-standing gap in mammalian bioacoustics. Angela Stoeger, Mammal Communication Group of the Biology Cluster of the Acoustic Research Institute, Austrian Academy of Sciences, will lead this study.