Overview of Research in the Animal Communication Lab - Evolution and Mechanisms of Animal Acoustic Communication

As the Nobel Laureate Niko Tinbergen pointed out, gaining a complete understanding of an animal's behavior requires knowing the behavior's evolutionary history, its function and development in the present environment, and its underlying mechanisms. In other words, ABCDEF:

Animal Behavior = Causation + Development + Evolution + Function

What Tinbergen taught us is that understanding animal behavior requires an integrative, comparative, and multi-disciplinary approach that investigates different aspects of the whole organism. Research in the Animal Communication Lab takes just such an approach, drawing on questions and methods from behavior, ecology, evolutionary biology, comparative psychology and neurophysiology to investigate acoustic communication. The over-arching goal of our research is to understanding what, why, and how information is conveyed in acoustic communication signals. The general questions we address are (1) how do animals encode information about themselves in acoustic signals? (2) how do animals acquire information about other conspecifics through the perception of acoustic signals? (3) how do these processes function in natural habitats and noisy social environments? and (4) how have these processes evolved?

In the Animal Communication Lab, we primarily use anuran amphibians (frogs and toads) as model organisms to investigate these questions because they are among the most vocal of all vertebrates. In frogs, acoustic communication plays important roles in species recognition and sexual selection (female mate choice and male-male competition). We are particularly interested in understanding the role of communication in mediating female mate choice and male-male competition, and the operation of communication in social environments that are extremely noisy and both temporally and spatially variable. Frogs offer powerful model systems for addressing these questions because (i) male frogs signal in large breeding aggregations, they use acoustic signals to defend calling sites, and they have a relatively small repertoire of stereotyped acoustic signals; (ii) female frogs choose mates based primarily on the acoustic properties of male signals; (iii) both male and female frogs are amenable to field and laboratory playback studies using real and computer-generated signals; and (iv) acoustic communication in frogs can be studied at multiple levels, from broad evolutionary patterns to the responses of single neurons. Our long-term research goals are to answer questions about acoustic communication at multiple levels of analysis, such as:

Ecological level: How is the use and perception of acoustic signals determined by the habitat characteristics and local densities of other acoustically signaling individuals, which together influence the attenuation and degradation of sounds, the background noise levels, and the levels of intraspecific and interspecific competition for "acoustic space"? What are the effects of antrhopogenic noise on animal acoustic communication systems and how are these effects linked to population viability?

Evolutionary level: What aspects of the vertebrate hearing system have evolved for the general purpose of hearing, and what special adaptations have evolved to improve the detection and recognition of conspecific acoustic signals? What are the sources and roles of constraints on perceptual processing in the evolution of acoustic pattern recognition and social recognition systems? How have similar natural selection pressures arising from similar mating systems operated within constraints imposed by different signaling and sensory systems? What are the ultimate causes of plasticity of signaling in the context of male-male aggression? Are signals always inherently honest, or can bluffing be evolutionarily stable?

Behavioral level: How do animals mediate the level of signaling in different behavioral contexts? What are the relationships between vocally mediated species recognition and individual recognition? How do animals assess the resource holding potential of rivals in competitive interactions? To what extent do communication networks function in frog choruses?

Perceptual level: Do animals perceive different conspecific signal variants, such as advertisement and aggressive calls, or the signals of different individuals, continuously or categorically? What are the acoustic and perceptual cues that underlie vocally mediated social recognition? How does the anuran auditory system form perceptual "auditory objects" of acoustic signals and segregate these perceptual objects from the background noise of a loud chorus?

Physiological level: What are the proximate mechanisms involved in the adaptive plasticity of signaling in the context of male-male aggression? How does the auditory system construct meaningful perceptual representations of acoustic signals in noisy backgrounds? How does the nervous system form enduring representations of a conspecific's vocalizations in the context of vocally mediated social recognition?