Accelerometers are devices that measure changes in acceleration relative to an inertial frame of reference. Measured acceleration can be static (the force of gravity), or dynamic (the forces moving the device itself). Measuring static acceleration allows us to ascertain the orientation of the device in relation to its pull to the earth. Determining dynamic acceleration involves the detection of the physical movements of the device in various axes of acceleration outside the inertial constant of gravity.
Accelerometers exist in many forms and are utilised in a range of fields including engineering, industry, navigation, medicine and biology.
Accelerometer with transmitter attached
Within the field of biology, accelerometers are revolutionising the study of animal behaviour and bioenergetics. High frequency data recording (>10Hz) with the use of bi-axial and tri-axial accelerometers allow for the discrimination of behavioural patterns and metabolic performance in animals. Such studies include birds, fish, amphibians and mammals as their subject. Studying animals that occupy the aquatic realm of our planet has proven challenging, due to the naturally concealing nature of their environment. Accelerometry studies have flourished in this area as tools to overcome this obstacle.
To date, accelerometers have been employed in aquatic studies to identify mating events in sharks, feeding behaviours in seals, swimming kinematics in penguins and metabolic rate in fish, to list just a few examples. As accelerometer technology progresses in tandem with the development of applications in the field, they could easily become the key to unlocking many more mysteries in the animal world.
Accelerometer attached to the dorsal fin
Accelerometer attached to a juvenile
lemon shark (Negaprion brevirostris)
Here in Bimini we are using tri-axial accelerometers in research projects to assess the fine-scale natural behavioural patterns of, and attain a field metabolic rate for, the resident lemon shark population (see current research page for more info). Accelerometer tags are appended to the sharks 1st dorsal fin using monofilament and crimps. Sharks are then released back into the wild and are observed behaving naturally for 5 days, during which time the tag archives all acceleration data. Sharks are then re-captured, the accelerometers recovered and downloaded, and the data analysed.