Understanding the functional mechanisms and evolutionary origins of animal communication through substrate borne vibration is an important problem in behavioral ecology. The availability of technologies such as portable laser Doppler vibrometers, highly sensitive piezoelectric films and transducers, and portable neurophysiology preparations allow investigators to address a broad array of questions associated with vibrational communication. This research tests hypotheses regarding the form, function, fitness implications, ontogeny, and phylogeny of vibrational communication among the extant New Zealand Deinacrida. This work addresses the following questions with respect to each of the eleven species of New Zealand giant weta: 1) Does the species produce vibrational signals for the purpose of intraspecific communication, and if so what are the spectral and temporal characteristics of the signals? 2) What is the neurophysiological range of response to seismic stimuli in the species? 3) Under what social contexts are the signals produced, and does signal character change with context? 4) What are the fitness related implications for vibrational signaling in the species (assessment benefits in inter male contests, female assessment of mate condition)? 5) How does the use of vibration change over the course of development in the species (predator avoidance to reproductive function)? 6) How do the form and function of vibrational signals compare between species? , and 7) Is there a relationship between vibrational signaling and ecological niche?
In the last two decades there has been a growing interest in understanding the functional mechanisms and evolutionary origins of animal communication. New technologies such as portable laser Doppler vibrometers allow investigators to address a broad array of questions associated with vibrational communication in insects. This work will improve understanding of the selective pressures and evolutionary patterns that have resulted in the prevalence of vibrational signaling for communication. Using laser Doppler vibrometry in the field, extracellular electrophysiology in the laboratory, together with sound and high-speed video analysis of the New Zealand giant weta, key hypotheses in vibrative communication will be tested. Data collection and analysis will be performed by undergraduate research students from Augustana College and by students of Maori descent enrolled at Victoria University of Wellington.
In this NSF Research Starter Grant, the awardee Dr. Daniel R. Howard leveraged the support of the award to establish the technical infrastructure and support travel to study the functional mechanisms underlying the evolution of vibrational communication in a group of primitive, flightless insects (giant weta) found only in New Zealand. The scientific community has become increasingly aware of the prevalence of this cryptic or "private" channel of communication in animals as our ability to reliably detect and record these signals has improved, but it remains unclear how vibrational communication evolves across different ecological settings, and how vibration may compliment other communication modalities. In this study Dr. Howard involved undergraduate research students from Augustana College, Sioux Falls, South Dakota in conducting field and laboratory studies with local stakeholders on Maori-owned lands in New Zealand that resulted in new discoveries in animal behavior. Findings show that in one species, the Cook Strait giant weta, males competing for the attention of a mate will use vibrational signals to settle rivalry bouts with other males with little to no physical altercation. In another alpine species that lives in rocky scree fields and does not use vibration, fighting between rival males typically escalates into violent confrontations. Thus the nocturnal giant weta, a group that lacks wings and thus cannot produce sound like other related Orthopterans, appear to use vibrational communication under the cover of darkness as a silent mechanism to lower the cost of conflict. Students involved in the research were trained in how to conduct behavioral experiments, collect and analyze vibrational recordings, and conduct vibrational playback experiments. They have submitted for publication a first-authored scientific paper that describe these results, have presented their findings at multiple scientific meetings, and the research has set the stage for future domestic and international studies that seek to expand our understanding of how animals use vibration to solve a myriad of life challenges.
