Georgia Southern University
During the first quarter of 2019, my spring semester Field Biology class and I officially launched the SInGS (Singing Insects of Georgia Southern) project. During the initial phase, students learned basic GPS skills, how to describe habitats, and how to set up and install Song Meters. We identified five sites on the Statesboro campus that represented different habitat types (woodland, wetland, sand hill, disturbed, and urban (Fig. 1), and installed one Song Meter at each site on February 21 (Fig. 2). We set the meters to record five minutes every hour at a sample rate of 44,1000 Hz. We also set up a schedule to swap out the batteries and SD cards on a monthly basis (Fig. 3).
In the classroom, students learned the mechanisms and functions of sound production in animals, how to describe and analyze animal sounds, and how to use the Open Source audio analysis software Audacity to facilitate the location and characterization of insect calls. An earlier class surveyed the University of Florida’s “Singing Insects of North America” website and constructed a list of 92 species of orthopterans (44 crickets and 48 katydids).
This semester's class had the formidable task of characterizing the songs of each of these species (trills, ticks, chirps; peak frequencies, duration, complexity, variability, etc.) and assembling this information into a novel, spreadsheet-based identification aid. We engaged in a trial run of this Audacity-spreadsheet approach to audio identification by having the entire class attempt to identify two species of orthopterans in the same five-minute file.
Based on the outcomes of this trial run, we tweaked the identification protocols as well as the guide itself. In late April students will each work through 24-25 files, identifying any singing insects they hear/see and identifying patterns of change over time (during a day, across the season) and differences among the five sites. During the April maintenance visit to each site, students collected specimens using sweep nets, beater trays, and pitfall traps to compare and contrast with the audio surveys.
During the second quarter of 2019, my spring semester Field Biology class maintained the five Song Meters installed in different habitats across campus as part of the SInGS (Singing Insects of Georgia Southern) project. Each month they replaced the batteries, swapped out the SD cards, and downloaded the thousands of files for later inspection. They also sampled habitats with sweep nets, beating trays, and pitfall traps (figs. 1-3). Curiously, although we heard (adult) insects singing, nearly all of the orthopterans collected by these methods were nymphs. In late April, students were assigned 24 or 25 five-minute files, selected to allow them to evaluate one of four questions concerning singing insect activity:
How does activity vary at one site over a single 24-hour interval?
How does activity vary at one site over a 90-day interval (from mid-February through mid-April) over five time intervals?
How does activity vary across all five sites over five time intervals on the same day?
How does activity vary across all five sites at the same time over five different days during a 90-day interval?
Their task was to keep track of and attempt to identify any singing insects they hear (or see, using Audacity) in these files, using the skills they acquired in class and the audio identification guide the class produced. Not surprisingly, some students were better at this task than others, although overall they were reasonably accurate in their identifications. The high diversity of unfamiliar sounds (they had nearly 100 species of crickets and katydids to choose from) definitely complicated their ability to efficiently identify and learn species and thus efficiently process dozens of files. Unfortunately, we started this phase of the project too late in the semester, and class ended before we could really explore their results in depth.
For the current crop of Field Biology students (Fall 2019), I have made a couple of adjustments: first, we entered the acoustic portion of the class within the first few weeks, and second, we are focusing on cicadas (14 potential species) rather than singing orthopterans (98 potential species). They have been familiarizing themselves with the calls, and will hopefully start listening to Song Meter files in the next couple of weeks.
Fig. 1: Five Song Meter installation sites on the Georgia Southern University Statesboro campus. A: disturbed (woodland bush-hogged, leaving a clearing with rapid-growing brambles and other early succession plants. B: sand hill. C: pine woodland. D: wetland. E: urban campus.
Fig. 2: Field Biology students and professor finish attaching a Song Meter to a tree adjacent to a pond (offscreen) in the wetland site. Pictured from left to right: Courtney Weekley, Kayla Dunn (obscured), Kianna Reed, and Alan Harvey. Photo by Kensley Depenhart.
Figure 3: Field Biology students replacing batteries and SD card during monthly maintenance of Song Meters. Pictured from left to right: Dillon Hernandez and Brandon Jarvis. Photo by Alan Harvey.