Field studies of animals involve observing and documenting their behaviors. However, many animals are a challenge to study because they are secretive or because they live in environments too dangerous or inhospitable for humans. Over the last ten years many scientists have increasingly turned to devices called accelerometers that allow them to exhaustively document what an animal is doing, even if the nearest human is miles away.
Accelerometers are small devices, typically weighing less than an ounce, which can detect changes in orientation. If you own a smartphone, camera, or tablet, there is a good chance you own an accelerometer as well. They allow your device to detect when it has been turned on its side so that your screen can be displayed correctly.
When slightly more sophisticated accelerometers are attached to animals, they can simultaneously detect and record front-to-back, side-to-side, and up-and-down motion as the animal goes about its normal activities. Importantly, different activities generate distinct patterns of measurements. Simple behaviors like walking, running, or trotting can be easily distinguished from one another with minimal effort. However some behaviors like eating, may not be as easy to pick out from the raw data. In such cases, scientists can match their direct observations of behaviors with corresponding accelerometer measurements, and then use these paired observations to train software to recognize similar patterns elsewhere in the data set. This approach can be used to reconstruct what animals were doing while no one was around to watch.
In addition to tracking behavior, accelerometers are also capable of measuring how much energy animals use. Energy expenditure is important to biologists because it is closely tied to survival and reproduction. Before accelerometers, tracking energy expenditure in wild animals was both invasive and costly, making it impractical for many projects. Accelerometer data on energy use has already provided new insights into how animals make decisions concerning where to move. For example, imperial cormorants (Phalacrocorax atriceps) are birds that form colonies on land but forage in the ocean. One study that used accelerometers to track their energy expenditure found that they prefer to search for food in areas that require them to spend the least amount of energy. This probably allows them to maximize the energy they gain from their food and explains why certain individuals might travel several kilometers to feed rather than stay closer to home.
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- R. P. Wilson, F. Quintana, V. J. Hobson, Construction of energy landscapes can clarify the movement and distribution of foraging animals. Proceedings. Biological sciences / The Royal Society 279, 975-980 (2012).
- D. D. Brown, R. Kays, M. Wikelski, R. Wilson, A. P. Klimley, Observing the unwatchable through acceleration logging of animal behavior. Animal Biotelemetry 1, 1-20 (2013).
- R. P. Wilson et al., Moving towards acceleration for estimates of activity-specific metabolic rate in free-living animals: the case of the cormorant. Journal of Animal Ecology 75, 1081-1090 (2006).
- R. Nathan et al., Using tri-axial acceleration data to identify behavioral modes of free-ranging animals: general concepts and tools illustrated for griffon vultures. The Journal of Experimental Biology 215, 986-996 (2012).