Rats damage crops, foul human food, eat through wiring causing electrical outages and fires in buildings, gnaw through wiring harnesses in motor vehicles, consume the eggs of endangered birds and reptiles, and spread infection. All told, the cost to the U S. economy is estimated at $19 billion annually. And with 75 percent of the world’s human population expected to live in urban environments by the year 2050, the impact of rats is expected to get worse.
Yet, little is known about rat behavior, because rats are hard to track. GPS devices and other radio transmitters used on animals to understand feeding and social and migratory behavior don’t work on rats, because the rodents often spend a lot time in buildings, pipes and below-ground areas where signals cannot be received.
Two researchers at Hofstra University, in Hempstead, N.Y., are working to change that by RFID-tagging New York City rats. Ronald J. Sarno, an associate professor of biology, and Michael H. Parsons, a chemical ecologist, tagged 13 rats (nine males and four females) with Trovan ID-100US Universal Series implantable transponders. The low-frequency devices are roughly the size of a grain of rice and have a read range of approximately 7 inches. Sarno and Parsons used soiled rat bedding to attract the rats to an RFID reader with an antenna, a camera trap and a scale, to record their presence and weight.
Seven of eight rats that were caught and released within 10 meters (33 feet) of the reader returned to the reader at least once (the RFID tag dislodged from the other animal). All told, the rats visited the reader 397 times. No animals captured and released 20 meters to 50 meters from the antenna returned to the antenna. The researchers found that some rats were active throughout the day, rather than nocturnal as popularly portrayed, and they tended to stay in one area as long as food and harborage was available.
The goal of the research, Parsons says, was “to overcome the barriers holding back urban rat research by handling wild rats in a manner that was safe for the researchers [and rats], and by using remote sensing to identify individual animals and gain insights into their private lives.” The researchers plan to continue their studies into the behavior and ecology of rats, and believe they may have opened a new avenue for others.
When we have a better understanding of rats’ behavior, Sarno says, “the pest-control professionals will be able to control [rats] more effectively, and the urban environment will ultimately be safer.”