Dept. of Behavioral and Cognitive Biology, Faculty of Life Sciences, University of Vienna

1. Rhythmic entrainment and timing in elephants

In the last decade clear evidence has accumulated that elephants are capable of vocal production learning. Examples of vocal imitation are documented in African (Loxodonta africana) and Asian (Elephas maximus) elephants (reviewed in 1), but little is known about the function of vocal learning within the natural communication systems of either species. We are also just starting to identify the neural basis of elephant vocalizations. The African elephant diencephalon and brainstem possess specializations related to aspects of neural information processing in the motor system (affecting the timing and learning of trunk movements) and the auditory and vocalization system (1). The vocal learning and rhythmical entrainment hypothesis raised by Patel (2) suggests that a direct connection between the auditory centers and the motor planning regions (typical for vocal learners) is a prerequisite for the ability to synchronize with an auditory beat. This implies that only vocal learning species should be capable of rhythmical entrainment. Following this idea, elephants should, in theory, be capable of rhythmical entrainment. So far, an Asian elephant has been observed drumming a stable beat (3), and elephants in Asian tourist shows move rhythmically to music. Nonetheless, it remains unclear how much training was involved, whether the elephants spontaneously match their movements to the beat, or whether the accompanying music was chosen advantageously.

Within the frame of the proposed PhD project, elephants of both species will be tested on their abilities to synchronize their movements to rhythmic sounds.
Much of the group coordination in elephants - splitting up and reuniting which is typical for the fission- fusion society of elephants - is done via vocalizations (4), but little is known about timing abilities of elephants in the vocal domain. Therefore, timing and turn taking in communicative events (like in chorusing, and antiphonal contact calling) will further be investigated. Untangling the evolutionarily relationship between vocal learning, rhythmical entrainment and timing abilities (accurate timing is crucial in human speech and music) requires testing multiple species including non-vocal learners, however, equally important is investigating whether all vocal learners indeed possess the ability for rhythmical entrainment.

2. Cheetah sexual communication

In most mammals, vocal communication plays an important role during mating and reproduction. In several species, vocal signals have been shown to convey aspects of male quality used to attract females (1,2). Here, acoustic cues to the caller's physical attributes such as size, maturity or hormonal state are likely to be important but acoustic cues strongly vary depending on the mating system (3). Also, the importance and relevance of acoustic signals in relation to other modalities varies among species. Felidae are a highly vocal but considerably little studied mammalian family in terms of vocal behavior in general, and sexual communication in particular.

The aim of this project is to gain a better understanding of how vocal signaling mediates reproduction in Felidae with a focus on a highly endangered species, the cheetah (Acinonyx jubatus). Cheetahs produce a variety of vocalizations in a broad range of contexts (4), however, only little is known about the significance and the information conveyed by these signals. Cheetahs (as other cat species) produce vocalizations via two different laryngeal sound producing mechanisms, (1) via myoelastic-aerodynamic vocal fold vibration and vocal fold vibration via active muscle contractions ('purring'). Cheetahs particularly combine these mechanisms, which results in structurally complex transitional calls and combinations (4). Specifically in the mating context, both males and females do vocalize a lot, and males also constantly vocalize when encountering female odors. Thus, vocal displays seem a key factor for mate choice and also seem to initiate (perhaps even initiate estrous) and mediate mating behavior.
The proposed PhD thesis will take a broad bioacoustics and behavioral research approach by investigating and describing mating behavior and analyzing the structure and variation, the information content and the functional significance of male and female mating calls. Research will be conducted in zoological institutions in Europe and breeding sanctuaries in Southern Africa applying a multi-level methodological approach (including acoustic recordings, behavioral observations, taking physical measurements of trained cheetahs, fecal sampling for androgen / estrogen level analysis as well as conducting scent, and maybe, playback experiments).
In captive breeding programs, conservation managers intuitively use male vocalizations as an indicator of female receptiveness (pers. comm), however, females are extremely choosy and artificial insemination often is still the only way to successful reproduction. The findings of this PhD thesis shall improve knowledge of cheetahs' sexual communication in order to progress non-invasive assessment methods for breeding introductions leading to successful copulations.