What do you call an adult female crustacean with a tiny computer strapped to its back?
Robo-crab.
Scientists hope the backpack-toting animals will provide crucial insights into the life cycle of the Chesapeake Bay's female blue crabs and a boost to a population struggling to rebound after decades of overharvesting.
Specifically, the robo-crabs are answering what seem like two simple questions: After female crabs mate in the upper Chesapeake Bay, when do they start heading south? And how do they travel?
Finding that information - which could lead to adjustments in fishing sanctuaries for spawning females - has required more than a bit of creativity: The live, adult females are transformed into robo-crabs by strapping miniature computers to their backs. The 4-centimeter devices, built in a lab at North Carolina State University, contain instruments that record such data as water temperature, salinity and depth.
That's what happens every six minutes as the females make the long journey from the mating waters of Maryland to the spawning grounds of Virginia.
"With just $30 of parts, we can collect a wealth of information," said Thomas G. Wolcott, a professor of marine, earth and atmospheric sciences at North Carolina State. "We can take the data and basically re-create the path they take as they migrate down the bay."
The robo-crabs - a term Wolcott disavows but was coined by other scientists at the Smithsonian Environmental Research Center and National Oceanic & Atmospheric Administration - represent something of a technical compromise between the two most common methods of tracking animals.
Most of the time, scientists fix simple identifying tags to hundreds of animals, and the tags are returned when the animals are caught. Scientists rely on fishermen to record where they tags were recovered, and usually offer a few bucks for each tag to make it worthwhile for the fishermen. It's a low-cost, low-tech way to track population movement and size with three pieces of information: where the animal was released, where it was caught and how long it was loose.
For minute-by-minute records of animal activities, scientists use radio tracking devices, a process known as biotelemetry. But the gadgets are expensive, and for small marine animals, scientists often have to stay nearby on boats to keep a running log of data. Larger, more powerful transmitters that send data through satellites aren't feasible for most crab experiments.
