Leaping into the Future: PDAs as Frogloggers
July 2004
If a frog calls and there's no one to hear it, does it still make a sound? The answer is yes!
The development of automated recording systems, or "frogloggers," by Charles Peterson and Michael Dorcas in the early 1990s greatly enhanced the ability of researchers to monitor populations of calling anuran (frog and toad) amphibians. Automated recording permits continuous, 24-hour sampling and can be used to monitor several sites simultaneously. Thus, frogloggers are particularly useful for monitoring rare species that may be missed during field visits, and enable extended monitoring of calling anuran
communities in remote habitats that are difficult to access.
In 2001, the ARMI team at the USGS National Wetlands Research Center
(NWRC) in Lafayette, Louisiana, began improving the analog Peterson-Dorcas
frogloggers. NWRC used a series of electronic timers in the circuitry board to trigger hourly recordings and simultaneously register a voice time stamp. They added a 24-hour timer that allowed selection of recording times, and an auto-reversing variable-speed tape recorder to enable longer periods of recording time.
While the analog models opened many doors to monitoring amphibians, even the NWRC-improved devices still had several weaknesses. They were difficult to construct and maintain, cumbersome to carry in the field, and used analog tapes that can stretch, bleed, and break, and are difficult to store. To overcome these challenges, in the spring and summer of 2003 NWRC developed and tested a digital froglogger model. It consisted of a Palm-OS-based handheld computer (PDA) that was operated by proprietary software and included an internal microphone. The benefits of this digital froglogger are that the PDA requires no construction and is lightweight, and the calls are digitally recorded as .wav files, which can be directly uploaded to a computer for review and archiving. When tested in the field, the PDA frogloggers detected calls identifiably at distances at least 10m further than the analog frogloggers.
NWRC continues to explore improvements to the digital froglogger. They have been developing and testing customized software on PDAs with external microphone capabilities. They also have been pursuing a more modestly priced option of the
Peterson-Dorcas froglogger as a means to increase the affordability of frogloggers for everyone who wishes to monitor calling anurans.
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