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What instruments do scientists use to study marine mammals?

Scientists use instruments to collect data about the location and behavior of marine mammals.  The development of these instruments is practically a science by itself.  Luckily, as computer (and other) technologies advance, the instruments used to study marine mammal behavior improve.   Some of the instruments used to study marine mammals are:

Radio Transmitters

These instruments give out a signal that can be heard on a radio receiver, that can be connected to a computer to record the data. Radio transmitters can be used to indicate presence or absence at a colony. The signal can be heard when the animal is on land, and is absent when the animal is at sea.  Or may be used to indicate if the animal is at the water's surface or underwater. This helps to correct counts of animals that are often not visible. An animal with a radio transmitter can also be tracked at sea by researchers following the animal in a boat.

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Jim Lerczak readies his pole, attaches a suction-cup radio-tag to a passing beluga whale, and is then able to listen to the newly attached radio-tag. 

Time-depth Recorders

These instruments record how deep marine mammals dive while they are at sea, and allow scientists to look at differences in diving behavior between males and female animals, young and adult animals, and different species. The instrument records this information electronically, and the data can be transferred to a computer after the instrument is retrieved from the animal.  

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A Northern sea lion gets a time-depth recorder attached.

Geographic Location Time-depth Recorders  

These instruments are time-depth recorders that record light levels and surface water temperature when the animal is at the surface between dives.  They take advantage of new technology by using very accurate, yet small, clocks.  The light level recordings allow scientists to estimate the time of sunrise, noon, and sunset.   From these times, the longitude location of the animal can be calculated. The latitude of the location can be calculated from the estimated day length and the sea surface temperature measurements.  

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This male elephant seal was tracked with a geographic location time-depth recorder.   Find out more about this seal's travels!

Satellite-linked Transmitters

These instruments allow scientists to track animals at sea over a long period. The animal's location and dive information are retrieved from the instrument via satellite. This means that after the instrument is put on the animal, the scientist does not have to recapture to retrieve the instrument to get the information. This is very useful in remote areas where it is difficult to do research (a good example of this is Antarctica).


These instruments are passive listening devices that have actually been used for decades by the military to detect the presence of vessels (for example, submarines).   Because most marine mammals have species specific, underwater vocalizations, hydrophones are used to detect the presence and abundance of a particular species to determine when animals have started their annual migration.

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