After seeing an abnormally large rat scurry through a subway station or across a dark street in the city, it’s easy to wonder what’s being done to curb rat populations in major urban areas — especially in places like New York City. But the reasons behind these infestations are more complicated than they might first appear.

A recent survey presented in map-form in The New York Times plotted the “best and worst” areas in the Big Apple concerning issues like trash, safety and emergency services; rat control was listed as one of the lowest issues on the list in terms of overall satisfaction.

Rats are certainly not an unfamiliar sight in cities, but tackling the issue can be harder than it seems. There are many factors that come into play when attempting large-scale rat control in a city, and no single-pronged approach is likely to be successful. “Controlling rats in New York City — or any large megalopolis — requires a very comprehensive approach,” said Bobby Corrigan, an industry consultant and world-renowned rodentologist. “For the past 100 years, cities, the public and the pest control industry have all tried to solve city rat problems by merely placing out poison baits and using traps. But as is the same when managing deer herds in forests, or whales in the oceans — meaningful rat management requires detailed science,” he said, coupled with careful coordination with various city agencies and departments (e.g., sanitation, housing, parks, sewer/water, etc.)

There have been efforts to further understand rat populations in cities, but general knowledge of how the pest operates is still very limited. According to “Trends in Urban Rat Ecology,” an article published by the Journal of Urban Ecology, there is still much to be learned about how rats respond to smells in their environment; their decision-making; gender- and age-dependent behaviors; changes in behavior over time; and factors driving social structure and conflict.

The article suggests that so little is known about rat behavior partially because of an unwillingness to study them. Rats are seen as a public health pest because of their potential to carry disease, which leaves tenants, landlords and pest management professionals (PMPs) with a choice: either let the rats continue to live in an area in order to study them and learn how to control the problem in the long run, or take the quick approach and get rid of the infestation as quickly as possible.

Michael Parsons, a co-author of “Trends in Urban Rat Ecology,” attributes this knowledge gap to a lack of funding. When PMPs have little incentive to let rat populations persist, “municipal entities need to get behind academic research,” Parsons said. “How did we become the first nation to land on the moon? We had committed government funding research until dreams became reality. Is disease prevention not enough to warrant publicly available funding?”

Rat studies performed in the past would almost certainly not be accepted today, according to “Trends in Urban Rat Ecology.” The article cites a few instances in the 1940s and 1950s, in which rats were captured, tagged and released back into the city, and in which some rats were introduced to wild colonies — a practice that ended in “immigrant (rats) being mauled in violent conflicts with resident animals.”  

That’s not to say cities today are lax in their rat control research and control efforts. Corrigan noted that New York City has granted about $37 million in the past five years, some of which is being used to develop new methods of rat control. However, locals still might not be ready to shift their opinion on the topic.

“Because this is not a very visible ‘tangible product’ that the public can see, and because science takes sometimes a few years to pay off, [the research] sometimes is not appreciated — the lay public, the general public and the media can sometimes be frustrated, saying the city is not doing enough to exterminate the rats. The fact is, the city of New York should be applauded that it has finally — perhaps better late than never — initiated a scientific approach to managing urban rats.”

Both Corrigan and Parsons felt New York City residents were right to be disappointed in the city’s past rat control efforts. Parsons said neighborhoods with better waste management and less construction are probably more satisfied than others with the level of rats in the area. “I would ask cheekily, ‘What rat control?’ Waste sits out all night, every night. Rats are trap-shy, there is some [resistance] to first- and second-generation rodenticides, dry ice is no longer allowed [although that may be changing] and immuno-contraceptives have ineffective delivery mechanisms.”

Corrigan said he wasn’t surprised by any of the problematic areas noted on the Times map, but he said attention should be focused on any areas that all of the sudden begin to have larger rat problems compared to a few years ago.

Although progress is being made, without proper incentives to nudge rat research and management in the right direction, the gaps in knowledge might not be closed.

“We have known other researchers who were interested in rats, but they ultimately gave up — one at a time,” Parsons said. “I do not blame them. It is easier to get funding to conserve a rare animal on the other side of the world than it is to research novel, but promising, methods of rat control.”

The author is based in Athens, Ohio and can be contacted at swolfe@gie.net.