Scientists Have A New Way To Track New York City Rats

They could finally answer some questions about the rodents’ behavior and effect on human health

Image: Tara Jacoby / Photo: Getty
Jul 14, 2016 at 5:30 PM ET

It’s shockingly difficult to track rats in a city. Now a team led by researchers from Hofstra University have come up with a new way to tag rats and answer some basic questions about their behavior, and about how they might affect their human neighbors, according to a study published Thursday in the journal Frontiers in Public Health.

Scientists estimate that there are anywhere from 2 million to 32 million rats in New York City—an extremely large range. These numbers can fluctuate widely based on the season, Michael Parsons, a research associate at Hofstra University and one of the authors of the study, tells Vocativ, “But we don’t know because [the rats] are hidden.” They live around us and with us, but we know little about them. And because rats run into small holes in buildings and deep underground, radio-based tracking collars or devices don’t work to track them. Even less is known about rats on an individual level; viral videos like pizza rat and pita rat show the “top 1 percent boldest rats,” Parsons adds

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Rats are interesting not just because they are our rodent shadows—they will also play a much larger role in public health. The number of people living in cities is growing (75 percent of the world’s population is expected to live in urban places by 2050), which means they will increasingly come into contact with these urban-dwelling vermin. Unfortunately, rats carry a number of bacteria and parasites that can cause diseases such as salmonellosis, rat bite fever, and even the bubonic plague in humans. Even more unsettling is that researchers don’t know just how many diseases they might spread—a 2014 study of just 133 New York City rats uncovered 18 viruses that were previously unknown to science, but structurally similar to viruses known to cause disease.

The lack of knowledge about rats, plus their potential impact on public health, inspired Parsons and his collaborators to try a new protocol for tracking them. The researchers first set up several humane traps and lured rats to them using urine-covered cloth (“Males and females go nuts around their own scents,” Parsons says). A trapcam positioned around the lure gave the researchers insight into their social behaviors. For the rats in the traps, the researchers would anesthetize them, took blood and fecal samples to look for pathogens, and implanted a barcode-like tracker between their shoulder blades.

The implant, about the size of a grain of rice, is a radio frequency identification (RFID) device, a barcode that allows the researchers to track the rat’s information when they recapture it. When Parsons and his team tried out the protocol on 13 rats for a separate study published in December, it took them over two hours per rat at first. But by the end they could complete the procedure in about 12 minutes, Parsons says.  

This experiment was just a pilot project. If he gets funding to expand the study, Parsons hopes that repeated measurements can help scientists answer some basic questions about rat behavior and biology, like how much their populations or disease-carrying capacity fluctuate between seasons. It could also help them prove (or disprove) aspects of their behavior that researchers already suspect are true, like that “rat kings,” a phenomenon in which many rats become fused together by getting their tails tangled up, might be real. 

Ultimately, Parsons hopes that new information about rats could help prevent public health disasters before they occur. “If rats are carrying unknown viruses similar to things that make us sick, shouldn’t we be looking more carefully on a regular basis?” he says.