C-PODs - Cetacean and Porpoise Detector

Harbor porpoises orient themselves by echolocation using short, high-frequency, narrow-band clicks that are emitted almost continuously. These can be single clicks as well as click sequences consisting of several clicks emitted in succession. These acoustic sequences are recorded with harbor porpoise click detectors, so-called C-PODs, as part of passive acoustic monitoring.

How it works

The harbor porpoise detectors are autonomous recording devices that record these high-frequency echolocation sounds of harbor porpoises and other toothed whales using a built-in underwater microphone (hydrophone). Specifically, a C-POD consists of a hydrophone, an amplifier, frequency filters, two battery units, and a digital memory card housed in a pressure-resistant plastic case. The hydrophone omnidirectionally records all sound events with a click characteristic in a frequency range of 20 to 145 kHz or 160 kHz (depending on the C-POD version). This covers the typical frequency range of harbor porpoises from 100 to 140 kHz. After presetting different filters, the C-POD captures the physical characteristics of the registered sound events. Main frequency, frequency response, sound duration, sound pressure level (in 8 bit steps), frequency bandwidth and the envelope of the signal are stored digitally for each individual click on an SD card. The recorded sounds are later automatically searched for porpoise-specific signals using special software.

Areas and scopes of application

  • Click detectors can continuously record data on the presence and seasonal use of an area (habitat use) by harbor porpoises at a narrowly defined location
  • A spatio-temporal pattern of use is derived from these continuous ecological data sets
  • research and construction projects
  • IfAÖ deployed the first devices in 2008. The devices are used in Germany and abroad
  • On request, we also lend out equipment and/or provide advice on the analysis of the data
  • Together with the observation data from aircraft and vessel censuses and the DAISI surveys, they form the basis for environmental reports and research reports


Dr. rer. nat.
Bente Limmer

T +49 151 53837257
E b.limmer(at)ifaoe.de