Influence of Acoustic Signals on Reproduction, Including Infrasound and Ultrasound in Mammals

The novel research field of sensory ecology examines how animal communication relates to ecology, physiology, social dynamics, and reproductive success. In developing new techniques to examine animal vocalizations, scientists in the Behavioral Biology Division of CRES can obtain a better understanding of how animals perceive their surroundings and one another.

Many animals use their sense of sound and smell preferentially over visual cues for communication, and these sensory modalities need to be understood in order to aid the advancement of conservation biology. The Behavioral Biology Division's primary goal is to assemble a collection of calls or vocal repertoires from key focal species within the Zoological Society of San Diego's collection in order to examine the behavioral context of acoustic signals. Indeed, research in bio-acoustic communication could be one key to improving managed care and breeding of rare and endangered species. Techniques developed within the laboratory will be used in the field to augment pre-existing research projects.

The specific aim of this project is to record and study vocalizations in species that utilize a wide frequency range within their calls. Such communication includes frequencies that are within the normal audible range of humans and also sounds that are either too high (ultrasound) or too low (infrasound) for us to hear. Calls at the extremes of the auditory spectrum are understudied but are extremely important to understand. They are believed to relate to how individuals recognize potential mates, influence fecundity, and maintain mother-infant bonds. By using very sensitive microphones and associated computer software we can examine the full vocal range of each respective species to ascertain behavioral meaning and any subsequent effects upon endocrine response and reproductive success.

The initial focal species in the collection that commonly utilize infrasound include elephants, giraffes, and okapis. Ultrasound is to be studied in slender lorises, who are thought to use high pitched vocalizations during the first 120 days of infant development when the baby is isolated visually from the mother, and in dholes, which utilize such frequencies in relation to cooperative breeding.