The relevance of acoustics for giraffe behavior and ecology

Vocal communication is a crucial component for information exchange in species living in fission-fusion social systems, in which groups merge of and split into subunits such as in African elephants, spotted hyenas and dolphins. Despite the fact that giraffes live in such dynamic societies, the role of vocal signals for mediating social interactions or regulating group compositions remains a largely underexplored aspect of giraffe behavior and ecology. Although it has been demonstrated that giraffes produce various audible non-vocal and tonal sounds, interpretations on how and when they utilize vocalizations still derive mainly from opportunistic observations and untested assumptions. For instance, it is assumed that giraffes, like elephants, use infrasound for long-distance communication, and make use of a different sound production mechanism. Instead of vocal fold vibrations that most mammals use for sound production, it has been suggested that giraffes use neck and head throws to generate infrasonic frequencies. Colleagues and I characterized an entirely new vocalization in zoo-kept giraffes, termed hum, a tonal low- frequency call. The fact that the hum was recorded only at night suggests that giraffes might be more vocal in the absence of visual communication cues. Further, its acoustic structure provides important indications on the vocal production mechanism and the potential functional relevance of this particular vocalization to convey biological information to receivers. To date, no experimental research approaches were undertaken to understand the function of acoustic signals in giraffes. The overarching goal of the proposed research project is to quantify and qualify the giraffes vocal communication system, and to improve our understanding of sound production, auditory perception and social use of vocalizations in this iconic and vulnerable animal species. The proposed project aims to combine classic bioacoustics and behavioral research tools and sophisticated experimental designs by using a zoo- and field-based research in tandem. Acoustic recordings with behavioral observations will shed light into the giraffes vocal behavior and vocal activity both under controlled and natural conditions. Additional acoustic playback experiments will be used to evaluate the giraffes perceptual abilities by investigating whether they are able to identify conspecifics and are capable of assessing the degree of predation risk based solely on vocalizations. The results in the proposed directions will gain considerable knowledge about giraffe vocal communication and create substantial interest in the research community.