As the sensor industry has matured we've seen the spread of sensors through the various manufacturing industries and into the goods and products we buy and use. Sensors are also making themselves useful in studying animals and birds, following their peregrinations and mapping their interactions. Whether it's motion-activated cameras, radio collars, or instrumented burrows, sensors provide tools for examining animals in their natural habitats.
New Caledonian crows are very, very bright birds, that can both use and make tools to aid their efforts to extract tasty, tasty insects from wherever they're hiding (the insects, not the crows). The question researchers from the University of St. Andrews and the University of Washington (UW) wanted to answer was how tool use spreads among the crows. The researchers used a special, very low-power wireless telemetry system developed at UW to map the birds' social interaction. Tiny proximity loggers on the birds record the date, time, and duration of a close encounter. Because the radio tags can both send and receive, signal strength was used to infer when two tagged birds were in close proximity. By collecting data on which birds were interacting with each other and for how long, the researchers could amass a large amount of data on the crows' social network. Turns out, New Caledonian crows are a pretty tight-knit bunch. (If you're interested in learning more about biologging, of which this is an example, read the paper "Biologging technologies: new tools for conservation. Introduction" by Steven Bograd, Barbara Block, Daniel Costa, and Brendan Godley in Endangered Species Research, published online in March 2010.)
Our previous example involved mobile tags communicating with fixed wireless gateways, but you can also use fixed systems that use acoustics to collect information on critters that make noise, such as mammals, birds, and frogs. By using microphone arrays you can, it turns out, track where an animal is within a monitored space by figuring out where their calls originate, and you don't have to catch and tag your creature of interest to do it. Canadian researchers published a paper on their field test of a wireless microphone array in the British Ecological Society's journal Methods in Ecology and Evolution (PDF). The equipment they field-tested is, they say, smaller, less expensive, and uses GPS to keep the microphones time-synchronized. Since few biology departments are awash in cash, cheaper and better equipment means more and better data for the researchers who rely on it.
It's not only the wild animals that are of interest, either. Consider, for example, the Danish researchers who used a wireless sensor network to monitor cows and the amount of time they spent in a pasture with a strip of new grass to munch. (The full paper published in 2008 in Computers and Electronics in Agriculture is available as a PDF here.) In their case, the goal was to monitor the grazing behavior in strip crop grazing, where the animals are presented with a fresh strip of pasture every few days.
In all of these applications people needed to collect data in challenging environments, and to do so without changing the behavior of the creatures being studied, whether those creatures were wild or domestic. That calls for a clever combination of both appropriate technologies and careful experimental design.