Oct 15, 2019A set of four RFID-enabled lures at a Brooklyn recycling site have provided new material for researchers regarding how rats behave in the wild, what scents they are attracted to and which scents they avoid. New York City colleges Fordham University and Columbia University, working with RFID technology company UID Identification Solutions, have spent more than a year tracking the behaviors of city rodents—not in captivity, but in their own environment—and have learned details about rats that simply couldn't be accessed in a lab.
The solution, which tracks how rats behave when they smell male and female rat scents, both in open and enclosed areas, has proven that rat research offers greater insight when the animals are taken out of labs and away from cages, says Michael H. Parsons, an urban environmentalist and visiting research scholar in Fordham's Department of Biological Sciences. "We felt that some of the results in the lab don't equate to what's in the field," he states.
While rat behavior has been conducted for years in controlled environments, Parsons explains, that's irrelevant to the behaviors of wild rats. Comparing lab rats to wild rats is like comparing a Chihuahua and a wolf, he says, adding that the behavior for any species would be different in a cage than in the wild. Because little research has taken place in rats' natural setting, he says, "No one understands the behavior of city rats, millions scurrying between our feet. No one knows what they're seeing."
When Parsons launched his rat-tracking project to understand the animals' reactions to scents, he was following up on similar research involving kangaroos in Australia. Several years ago, when he arrived in the United States, he began looking into one of cities' most ubiquitous animals. Rats are nocturnal, so their vision is limited and their sense of smell is heightened. That makes them highly responsive to scents, which could thus be used to control their behaviors, or to catch or sterilize them.
The researchers needed to track what individual rats do and where they travel over a span of time, Parsons says, and that required microchips to uniquely identify each animal. One of the project's greatest challenges was to find a business or property manager willing to have researchers catch rats on their property, then chip the animals and release them again. A Brooklyn waste-recycling site, which has asked to remain unnamed, agreed to do so, with the stipulation that the rats would be exterminated at the conclusion of the research. The research is currently still ongoing.
Fordham researchers worked with an animal-tracking technology firm, then began partnering with UID after the first company went out of operation. UID provides identification solutions that leverage implantable transponders (microchips), external readers, and customized data-collection software for researchers. The company focuses on laboratory animal identification, as well as pets, wildlife and zoological solutions, according to Matt Ruiter, UID's CSO, "but we were happy to custom build an application for less conventional settings," he says.
To enable their research on wild rats, Fordham and Columbia set up live traps to capture 50 rodents, then sedated the animals and injected a UID LF proprietary chip between each animal's shoulder blades. The unique ID number encoded on the chip was linked in UID's software to the description of the specific rat, such as its sex and approximate age and size. The rats were then released.
RFID reader deployment was challenging, Ruiter recalls, simply because it was such a unique application. The system needed to locate rodents in outdoor environments, and to be impervious to abuse from both weather conditions and the rats they were tracking. That meant making sure the technology was shielded from water and the chewing teeth of rodents. As such, the reader is housed in a ruggedized, waterproof box.
The hardware the team built consisted of a UID 134.2 kHz LF FID reader with four ports, and with a nine-foot cable attached to each. The antennas were embedded inside four industrial 0.75- or 1-inch plates. The researchers then applied two kinds of scents: male and female pheromones—a secreted hormone that rats can easily smell. They were located in open areas, as well as in more protected ones, such as against a wall. As each tagged animal passed over the antenna, it captured the animal's unique ID number. The single antenna that was connected to all four antennas then forwarded that data, along with a time and date stamp, back to a local server via a cellular connection.
Each antenna site comes with a camera. UID's software analyzes the collected data and sends a daily spreadsheet to researchers, indicating which rat was at which location, as well as when and for how long. The researchers can then refer to the video footage at those times to identify what was happening. While cameras alone could help collect behavior-based data, Parsons says, it would be difficult to identify a particular rat and, thus, its overall behavior.
The research team found that both male and female rats are attracted to female pheromones but are repelled by male pheromones. In open areas, they are more fearful of other male rats and were found to leave the site more quickly or simply never go there. Those reactions would have been less pronounced among lab rats, Parsons says, since the danger posed would be less pronounced.
The solution, which UID calls the Rat Tracker, is intended for use in industrial or urban settings. In the future, Ruiter says, the company could opt to include IP temperature-sensing microchips to potentially track the animals' health and weight, in order to understand if or what they are eating. It could also weigh each tagged animal as it passes over the antenna. "The end result is that the study could pave the way for more studies of rats or other animals in their own environments," Parsons states. "It gives them the best option to test animals in context in the field. I think we've stumbled onto a gold mine."
Arrow Exterminating has also worked with the researchers, including identifying where antennas should be placed, as well as the catching and anesthetizing of rats for microchipping purposes. "We needed an expert in rodent control," Parsons says, so that the team could understand "what it means to be a rat." Although the researchers chipped 50 animals, he note, only about 15 or 20 were discovered by the readers, in part due to poison baits and predators, such as hawks and raccoons.
The project's results have been published in the Journal of Urban Ecology, produced by Oxford University Press. The next step, Parsons reports, will be to expand the research to other sites, such as in Houston and Los Angeles.
