Note: This is an archive of my old Froglogger page. Some info may be out of date.
Automated Digital Recording Systems
I wanted to use a Froglogger to determine the highest periods of activity during the night for Eleutherodactylus frogs in Puerto Rico. However, I wanted to replace the tape recorder with a digital recorder to transfer easily the recordings to a computer for analysis and filtering. This was necessary because the most common frog in the island, E. coqui, occurs at high densities and its call is very loud, masking other species calls. Since most of the rest species of Eleutherodactylus in the island are endangered, it is imperative to find new populations to study and protect. Using software it is very easy to filter out E. coqui and listen for other species. A similar approach can be used in many areas around the world and in many situations.
Wildlife Acoustics have an automated recorder, the Song Meter.
The Bioacoustics Research Program of the Cornell Lab of Ornithology have Autonomous Recording Units, which seem to be based on an embedded computer. They have not released the details of their system but recently started leasing them.
The original Froglogger
The system described by Peterson & Dorcas (1994), and now commonly known as a Froglogger, enables the researcher to records audio without supervision for later analysis. This enables the monitoring of animal calls during intervals and long periods of time that would be impossible for a person or too expensive. For example, you can record a few minutes every hour during several days or weeks.
As an example of the important and valuable information that can be obtained only by using a Froglogger is the paper by Bridges and Dorcas (2000). They found that Rana sphenocephala, which was described previously as calling during early spring and early fall, was also very active calling during the summer, but between 2:00 and 5:00.
The name can be misleading, the Froglogger has many applications not only for frogs and toads, but also for many other animals that call, like insects, birds and mammals (including marine mammals using a hydrophone).
Acknowledgments – I want to thank the NSF-EPSCoR Graduate Fellowship for their support during initial development. Also S. Brandes who pointed me the recording capabilities of the Nomad 3 MP3 player. P. Bright wrote the first version of the program and built the prototype controller. My graduate advisor, John Thomlinson for his enthusiasm for these systems and Mitch Aide for his constant input of ideas and “challenges” to improve the systems.
- Bridges, A. S. and M. E. Dorcas. 2000. Temporal variation in anuran calling behavior: implications for surveys and monitoring programs. Copeia 2000: 587-592.
- Peterson, C. R., and M. E. Dorcas. 1994. Automated data acquisition. Pp. 47-57. In: Heyer, W. R., M. A. Donnelly, R. W. McDiarmid, L. C. Hayek, and M. S. Foster (eds.). Measuring and monitoring biological diversity: Standard methods for amphibians. Smithsonian Institution Press, Washington, D.C.
Frequently Asked Questions (FAQ)
- How do these systems work? These systems are very simple. The controller triggers the signals necessary for the recorder to start and stop recording according to the desired sampling periods. For the digital recorders these signals are transmitter to the recorder’s remote jack, while for cassette recorders the controller provides power during the desired sampling period.
- What other digital recorders can be used? To keep it as simple as possible, the recorder needs two qualities: record in uncompressed format and have some way to control it. Many MP3 players can record, but only in compressed formats (mp3, wma…), which removes information from the sound. If the recorder has a wired/infrared remote, it may be adapted as a Digital Froglogger. Just let me know if you know of any such models and I’ll look into it.
- Why there is no iPod Froglogger? No iPod has a microphone or line input. The only option I know is an add-on for an older generation iPod that had a small microphone, but this only recorded using a sampling rate of 8kHz, which makes it useful only to record voice notes.