In the battle of cats vs. rats, the rats are winning

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The first study to document interactions between feral cats and a wild rat colony finds that contrary to popular opinion, cats are not good predators of rats. In a novel approach, researchers monitored the behavior and movement of microchipped rats in the presence of cats living in the same area. They show the rats actively avoided the cats, and only recorded two rat kills in 79 days. Published as part of a special "rodent issue" in Frontiers in Ecology and Evolution, the findings add to growing evidence that any benefit of using cats to control city rats is outweighed by the threat they pose to birds and other urban wildlife.

"Like any prey, overestimate the risks of predation. In the presence of cats, they adjust their behavior to make themselves less apparent and spend more time in burrows," says the study's lead researcher Dr. Michael H. Parsons, a visiting scholar at Fordham University. "This raises questions about whether releasing cats in the city to control rats is worth the risks cats pose to wildlife."

People have long associated cats as the natural enemy of rats. However Australian and US researchers say cats prefer smaller, defenseless prey such as birds and smaller native wildlife—which makes cats a threat to urban ecosystems.

"New Yorkers often boast their rats 'aren't afraid of anything' and are the 'size of a cat'," says Parsons. "Yet cats are commonly released to control this relatively large, defensive and potentially dangerous prey."

"Until now, no one has provided good data on the number of city rats killed by cats," adds co-author Michael A. Deutsch, from Arrow Exterminating Company Inc. "But the data have been very clear as to the effect of cats on native wildlife."

When invaded a New York City waste recycling center, the researchers took the opportunity to correct the record. Their team was already studying a colony of more than 100 rats living inside the center, by microchipping and releasing the animals to study their life history. When the cats entered the research area, they set up motion-capture video cameras to quantify the effect of the cats on the rats—the first time this has been studied in a natural setting.

"We wanted to know whether the number of cats present would influence the number of rats observed, and vice versa," says Parsons. "We were also interested whether the presence of cats had any effect on eight common rat behaviors or their direction of movement."

The researchers examined 306 videos taken over 79 days. Although up to three cats were active beside the rat colony each day, only 20 stalking events, three kill attempts and two successful kills were recorded in this time. Both kills took place when cats found rats in hiding; the third attempt was an open-floor chase where the cat lost interest.

The videos also revealed that in the presence of cats, the rats spent less time in the open and more time moving to shelter.

"The presence of cats resulted in fewer rat sightings on the same or following day, while the presence of humans did not affect rat sightings," says Parsons. In contrast, the number of rats seen on a given day did not predict the number of cats seen on the following day.

"We already knew the average weight of the rats was 330 g, much more than a typical 15 g bird or 30 g mouse," says Parsons. "As such, we expected a low predation rate on the rats—and our study confirmed this."

"We are not saying that cats will not predate city rats, only that conditions must be right for it to happen," adds Deutsch. "The cat must be hungry, have no alternative less-risky food source, and usually needs the element of surprise."

The findings could explain why people continue to release cats as "natural" rat control tools. "People see fewer rats and assume it's because the cats have killed them—whereas it's actually due to the rats changing their behavior," says Parsons.

"The results of our study suggest the benefits of releasing cats are far outweighed by the risks to wildlife," he adds.

The research team plans to continue collecting data as part of their long-term study and will update their findings as new information becomes available.

"Much more research is needed to better understand the city rat problem, we hope our successes will compel others to perform similar studies in other venues," says Parsons.

But for now, in the battle of New York City and rats it appears the rats are winning.

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More information: Frontiers in Ecology and Evolution, DOI: 10.3389/fevo.2018.00146 ,
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Citation: In the battle of cats vs. rats, the rats are winning (2018, September 27) retrieved 18 July 2019 from
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Sep 27, 2018
"The results of our study suggest the benefits of releasing
cats are far outweighed by the risks to wildlife."

Cats are worthless, except to lubricate wood chippers.

Sep 27, 2018
Repeated studies have shown that pets including cats are good for mental health.

Sep 27, 2018
What about domestic cats ? One of ours is known as '005½' after taking six rats in a fortnight.
Her gracile sister chased the last rat from the hedge, so claimed an 'assist'...

Sep 27, 2018
Well, cats are skilled at manipulating humans. On the cat's terms of course. In cat terminology, humans have two designations. "Can-opener" and "useless".

Years ago, when I lived in Irvine CA. Large tracks of undeveloped land were fenced off from the developed areas. It was very noticeable that the housing tracts were rather devoid of small birds and other small critters. The housecats had done a thorough job of killing whatever they could reach.

It was the fenced-off grasslands while driving past, one could see clouds of various birds year around.

All gone now of course. Replaced by housing and hunted to the brink of extinction by the housecats. The coyotes had been culled and they were the main predator of cats.

I vaguely remember a study a few years ago, that electronically tracked neighborhood cats. The results,totaling up the daily body-counts was staggering!

Only the biggest, meanest tomcat would risk hunting rats when there is easier prey available.

Sep 27, 2018
to barakan--Yes, cats make good pets if they are kept strictly inside. But if they are allowed outside, they are very destructive to wildlife, including native rodents, which are desirable. To Nik_2213, Are you sure those were rats, and not mice your cat killed? Are you sure they were Norway rats, and not much smaller and gentler native rats, such as pack rats?

Sep 28, 2018
I wonder if the change in rat behavior in response to cats' presence affects the fitness of the colony. Maybe the change in rat behavior has some impact on their population?

Sep 28, 2018
I wonder if the change in rat behavior in response to cats' presence affects the fitness of the colony. Maybe the change in rat behavior has some impact on their population?

Sep 28, 2018
@A: They were BIG and a brownish-grey. The bolder, dappled ones, cross-bred from feral released pets, have all died off...

Sep 28, 2018
the irony here is that cats don't eat rats much because they are busy doing the same things rats are doing, eating human garbage.

EVERYONE who discusses the rat problem knows why it exists. because the city eliminated the requirement for steel garbage cans and legalized the use of plastic garbage bags MANY MANY decades ago.
YOU CAN BLAME THE PLASTIC INDUSTRY for the rat problem, because they lobbied and still do to make rat food accessible to rats because it profits them greatly.

the city could easily require steel ,solid lid encased garbage cans in public, but they do not. the result is a LOT of rats.

Sep 28, 2018
Which brings us to what does get rid of rats. Poison? Hmmmm....NYC tried that and has professional exterminators whose stories told to reporters and book writers make fantastic reading. Fact: a pair control a breeding area. Females without breeding areas are ridden to death or have the litter as they are consumed. Our paved roads are welcome mats as they are tactile followers. I recall an example of a town in Mexico rat-free prior to the paved highway into town. Why is our garbage in wheeled bin transported to steel containers and we are no longer allowed to burn garbage? Because of rats.

Sep 29, 2018
zeekm you need to check into who is bribing your local politicians. That is whom dictates method of garbage collection.

Our city required metal trash cans. It brings a tear to my eye, remembering the cooperation between scavengers.

The raccoons would flip the cans over and around would gather the all the other neighborhood pests, The coyotes, the skunks, the possums, the gulls, the crows, the rats, the flies, the pigeons, and probably more pests then I care to remember.

The big change in the local ecology came about when the municipalities and trash conglomerate agreed to command a switch to large, wheeled, heavy-duty plastic trash cans with hinged attached lids. Designed to be difficult for non-simians to knock over.

Within a couple of years many of those pests had moved on or starved. Finally the neighborhood cats could catch up with slaughtering any remaining young animals.

Out of the above list? The coyotes have been culled by Vector Control.
- cont'd -

Sep 29, 2018
- cont'd -
Infrequently an adult skunk will wander by. The crows are greatly depopulated of a re-occurring avian disease that has cut into their numbers for the last few years

And the biggest surprise? Hardly any flies now. I wonder if the plastic of the cans includes some sort of insecticide?.

A hidden cost to this, aside from a more boring neighborhood? Jobs. All those trash collectors became redundant as the trucks only need a single driver. Using hydraulic arms to pick-up, empty and drop each new can.

Think you could convince their landlords of the goodness of their tenants being unemployed?

Also a big savings for the company bottom-line was the drastic drop in workman's comp claims and medical bills.

It was not a Chinese worker who invented the wheelbarrow. It was his boss, the Mandarin who saw the potential of paying one man for three men's labor. Then pocketing the wages that would have supported two other families.

Sep 29, 2018
Raising livestock over a lifetime-- cattle, horses, hogs-- we always had a number of cats around but in my experience they were far better mousers and birders than ratters. In fact, I can only recall one mother cat who I would regularly see dragging rats 2/3 her size back to her broods.

That being said, the amount of animal feed that mice and birds eat or befoul with their waste is not insignificant. And I am talking about sparrows, black birds, starlings, and grackles, not robins, blue jays, or song birds.

The best control for rats is a zero policy on killing snakes. Bull, gopher and black snakes are far superior to cats for rural rat control. Unfortunately so many human beings have what is probably an instinctive fear of snakes, probably conserved in our brains from our evolutionary history as small, rodent-like creatures ourselves, that they will kill them on sight.

In cities and wild areas, feral cats need to be culled-- and outdoor domestic cats outlawed.

Oct 01, 2018
Where I live it is popular opinion that cats don't hunt rats, but mice. Youtube popular opinion is that terriers are exceptional at hunting and killing rats.

Oct 01, 2018
Our local rat population has exploded due to our city allowing chickens to be raised within the city limits.

Oct 17, 2018
Another very-dead grey rat on our kitchen door-step today...

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