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In summer In 2017, Michael Parsons found the urban paradise of his dreams: a Waste Management Transfer Station, aka a literary paradise, aka Rat's Paradise, in Brooklyn, New York. For nearly two years, the behavioral ecologist and visiting scientist at Fordham University was looking for a place to observe urban rodents in their natural habitat.
The problem was that he had to not only capture the creatures and tag them, but also release them. Rats are wildly successful animals, a success that is very expensive for health and trade. They spread diseases, eat away at infrastructure and demolish food stores, a disaster that costs tens of billions of dollars a year. But to stop them, researchers have to study them first. "As the saying goes: Know your enemy," says Parsons. "And the only way to know a rat is to catch him and release him to be able to observe him."
As it happened, many New Yorkers were in agreement with Parsons and his colleagues catching their rats, but almost no one was cool with the releasing party. So when he and his colleagues found a waste treatment facility ready to let them do their job, they found themselves out of the way. "I'm talking about adult men and women in tears here," says Parsons, "because this research is so important, and it's incredibly difficult to do."
But a few months after their investigation, they discovered with horror that five wild cats had infiltrated the waste treatment facility and had started patrolling the rat burrow entrances.
At first, Parsons and his colleagues assumed that felines were a deadly threat to their subjects. Then they hit them: they had no idea of the reaction of the rats. Few studies have documented the interactions between wildcats and wild rats. For a behaviorist like Parsons, the surprise arrival of cats offered an irresistible opportunity. They decided to let nature take its course.
Their observations, which researchers tell in the latest issue of Borders in ecology and evolution, revealed that cats were miserable predators of rats – a finding that not only contradicts popular perception, but also adds to the growing evidence that wildcats, increasingly deployed by major US cities a much greater threat for smaller and more vulnerable urban wildlife.
One of the camera traps inside the dust-covered waste treatment facility
Michael Parsons
Parson had devised his original experiment to study how concentrated rat pheromones attract and repel other rats. This configuration proved perfect for studying interactions between the cat and the rat. Before the arrival of the cats, he and his colleagues had caught about 60 rodents that they had weighed, measured and implanted with a microchip before releasing them into the dusty bowels of the waste treatment center. In a corner of the building heavily frequented by rats, researchers installed two photographic traps and a pair of RFID antennas that they coated with various rat pheromones. Whenever a chipped animal was passing an antenna, a data logger was recording its presence. Meanwhile, the cameras captured video footage of the rats' behavior in the presence of different pheromones.
When wild cats showed up, the researchers began to monitor rather the behavior of rats in the presence of cats and vice versa. "It was the coolest part," says Greg Glass, a disease ecologist at the University of Florida and an expert in rat control strategies, who was not associated with the disease. ;study. "It's one thing to show that cats do not have much impact on rat populations, but microchips and cameras allow these researchers to ask the question, so if cats do not kill rats , so what are they doing? " exactly?"
The answer: not much. In 79 days, the cameras recorded 306 cat-rat videos, but only 20 cases of criminal harassment and only two successful victories. In fact, the vast majority of the time, cats showed virtually no interest in rats.
It may be that rats are too big and too unhealthy for cats to disturb the hunt. Parsons says that cats prefer small prey like mice and birds, which usually weigh less than 30 grams. In contrast, rats from the Brooklyn waste treatment facility weigh an average of 339 grams. "It's just below a pound, but it's still a lot of rat," says Parsons. A larger rodent gives larger teeth, larger claws and a greater risk of injury to a cat. This is perhaps the reason why researchers have never recorded anyone who caught a rat on the ground. The only two to kill video-caught researchers occurred when a cat was able to ambush a cornered rat.
Not that cats had no effect: the videos also showed that rats spend less time outdoors and more time looking for shelter. This observation is marked by anecdotal evidence from programs that dispense sterilized and sterilized cats to homes and businesses with rat infestations. "People are not telling us that they have seen an increase in rodent carcasses," says Lauren Lipsey, vice president of community programs at the Humane Rescue Alliance in Washington DC. January 2017. "They tell us that rats no longer dig under their courtyards and patios – that cats only keep rats."
But from the point of view of pest control, keeping rodents out of sight is not a victory. In fact, it's probably not even a draw; It's not because you see fewer rats than they are not there, that they breed and proliferate as they do. "The rats are already very smart," said Glass, who served for many years at the Mayor's Rat Control Commission in Baltimore, Maryland. Often, he says, when you put pressure on them, "they just get a little smarter."
There is also the devastating influence of cats on other urban wild animals to consider. Evidence suggests that their impact on birds and small mammals is enormous and much greater than on rats. In 2013, researchers reporting in the journal Nature Communications According to estimates, cats annually kill up to 4 billion birds and 22 billion mammals in the United States, a statistic that probably makes it the largest source of human-induced mortality in birds and mammals US.
"For me, this suggests that the risks associated with cat release far outweigh the benefits of rat control," says Parsons, who points out that more research is needed. But in this particular waste treatment facility in this Brooklyn neighborhood, the rats seem to be doing well.
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