DTAG-2

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Deploying DTAG-2 on a Blainville’s beaked whale in the Canary Islands, Spain. Photo by University of La Laguna with permit from Canary Islands government. This animal is called Bertel! You can find more pictures of this individual by searching the code ‘MDH74’ in http://www.cetabase.info

The DTAG-2 was the first widely used version of the DTAG. Designed in 2001 at Woods Hole Oceanographic Institution by Johnson, Hurst and Shorter, it was first used in 2002 and devices are still in use. It is 21cm long and 10.5 cm wide. Versions have been made with one, two and four hydrophone channels, and with recording bandwidths up to 80 kHz. Up to 16 GB of memory is built-in giving the tag a recording duration of up to 20 hours depending on the sampling rate. The tag comprises an electronics unit and syntactic foam floation encased in a two-part polyethylene fairing. The electronics unit containing a rechargable Lithium battery, circuit boards and sensors is contained in a polyurethane bag filled with mineral oil for pressure compensation. The fairing is joined together by four 60 mm silicone suction cups in a square pattern. The tag dimensions are x by y and the weight in air is 330 g. The tag is about 20 g buoyant in water and so floats when it detaches from an animal. A nickel-chromium wire is used to vent the suction cups at a pre-programmed time to release the tag. A 148 MHz band (2 m) VHF beacon, embedded in the foam and powered by a separate non-rechargable battery, is used to track and recover the tag. Data is downloaded from the tag via an infra-red interface. The tag uses an early version of the X3 lossless audio compression algorithm to extend the recording time. In addition to sound, sensors in the tag include triaxial accelerometer, triaxial magnetometer, pressure, and temperature.