John Metcalfe was CityLab’s Bay Area bureau chief, covering climate change and the science of cities.
Hitting urban rodents in their reproductive systems may be the best thing to ever happen to them.
If rats had their own civil-rights lobby, it might be scurrying through Times Square right now, holding up teeny signs like, "Bureaucrats Out Of My Duplex Uterus."
That's because New York City is poised to slam down on the rodents with a revolutionary, biology-altering pilot experiment to shrink their natural populations. As you might've read in the Wall Street Journal, workers from an Arizona research company are conducting surveillance on rats in the subway system's garbage rooms. Soon enough, they plan to deploy bait stations loaded with chemicals that will neutralize the reproductive systems of female rats.
The next litter the ladies give birth to might be reduced by half. The following one could only involve two or three pups. After that, the mothers might not be able to conceive during any cycle in their lifetime. They'll be permanently shut out from experiencing the joy of raising (and occasionally eating) a squirming, squeaking mess of ratlets.
Should the world be outraged at this attempt to force-sterilize the rat horde of New York? And should New Yorkers be worried about this mysterious chemical that withers ovaries like sun-blasted grapes on the vine? The answer seems to be "nope" and "hardly," at least in this early stage. In fact, eating this anti-reproductive juice could be the best thing to happen to rats since New Yorkers invented and started dropping 99-cent pizza. Here's why.
IT'S LESS CRUEL
Over the course of history, humans have killed rats with bullets, fire, stick beatings, electrocution, having dogs tear them apart, making Rube Goldberg traps to drown them and other ethically questionable tactics. New York today uses an "integrated" approach to its pest problem involving sanitation, trapping and poisons.
One can argue (if one's not a rat) that "snap" traps are humane if they kill instantly. Sticky traps, not so much – would you care to expire with your face smothering in glue? And the poisons that exterminators employ can also be agonizing, whether they be older toxins like strychnine or cyanide or the newer wave of anticoagulants, which make rodents bleed internally. Anticoagulants are "not as benign as you might think," says People for the Ethical Treatment of Animals president Ingrid Newkirk. "You hope they crawl away and die in their burrow, weak from blood loss, but actually you can have brain hemorrhaging which is painful."
Count PETA as a supporter of this new sterilization effort for rats (not for dogs, though, as maintaining a set dosage schedule for larger-body-weight strays would be too impractical). "Nature will always trump whatever we try to do," says Newkirk, "so we might as well do something relatively kind than something that's cruel."
Poisons are not exactly perfect for humans, either, as anybody who's lived through the weeks-long stench of a rat decomposing in an undetermined location can attest to. A child who gets into the household rodenticide supply can bleed internally for weeks until a doctor makes the diagnosis of anticoagulant poisoning.
Contrast that to ContraPest, the substance that New York is relying upon to sterilize rodents in this exploratory program. The stuff was developed by SenesTech, a reproductive-science company in Flagstaff, Arizona, which is testing it out on the subway via a $1.1 million grant from the National Institutes of Health. The main ingredient is 4-vinylcyclohexene-diepoxide, a chemical that's been used to create models of human menopause in mice. "What the compound does is it specifically targets a cascade of events in the ovarian follicle, or where the egg is nested within the ovary. That cascade of events sets up the message that the cells will die," says SenesTech's CEO Loretta Mayer. In effect, the rodent succumbs to early-onset menopause – or as Mayer's colleagues started calling it, "mouseopause."
When the next Hurricane Sandy washes all this vinylcyclohexene into the water supply, can two-legged mommies expect to enjoy menopause, too? Mayer says there is "no evidence of that," given that large doses in human primates have shown no such effect. "When exposed to soil and water it breaks down into inactive compounds," she says. "It's also metabolized by the animal in approximately 15 minutes, so there's no environmental exposure."
IT SHARES THE BLAME WITH HUMANS
Nobody knows the current size of the rat population in New York. Their sheer range and ability to hide in plain sight makes that impossible. Their population is probably in the millions, and there's no indication it's under control.
Thanks to popularized video footage of the kind posted throughout this story, many folks assume the subway system is boot-deep in raging rodents. But the public perception of the subway as ultimate rat lair is false; it simply seems that way, because we're a captive audience waiting for a ride. A hilariously fat rat running to catch up with a departing N train is naturally going to draw our attention, and soon enough a load of traps and poison.
Even if they even live in the subway system, rats tend to hole up behind uncomfortable concrete walls or filthy platform baseboards like war refugees. It's not a paradise for them; it's a slum. The only reason they're living in the subway is because of us: prodigious garbage factories, constantly littering the environment with food shrapnel like gummed hotdog buns, mangled bagels and half-finished bags of chips.
"The public perception is that they're worse in the subway because subways have this sometimes spooky look to them when we look down the tunnel. But the fact of the matter is it's probably not one of their preferred habitats," says Bob Corrigan, an instructor at New York's Rodent Control Academy. Rather, rats tend to favor "lots of healthy soil that has good cover" where they're "protected from predators or the elements."
New York's flirting with chemo-sterilization acknowledges the hard truth that traditional methods of rat management have failed, partly because the small mammals have adapted to our slovenly behavior. The next time you spot a rat in the subway and think, Hey, get out of here, rat! the rodent could as well retort, Hey, don't throw your cheese danish on the tracks, idiot.
RATS WOULD LOVE TO EAT THIS TASTY BAIT
The SenesTech crew isn't putting out bait with the ovary-altering active ingredient, yet; they're kicking off by monitoring the population numbers and eating behavior of rats who scurry about in the subway's trash repositories, those locked rooms where garbage is stored until night trains haul it away. (Fun note: Ever see glistening, blackish streaks near garbage cans around ankle height? That could be a rodent "runway," caused by rats repeatedly brushing against the surface until a layer of oily secretions build up.)
The researchers want to comprehend the full nature of subway rats before proceeding. So they're testing out baits with different ingredients, tweaking the formula of ContraPest to suit the precise flavor cravings of the typical New York City rat. They track what rats eat with motion-sensor cameras and a Rhodamine dye in the bait that makes their whiskers and feces glow under a UV light. They trap and euthanize rats, measuring dye bands in the whiskers to determine how long they take between meals and studying their internal organs to learn about their reproductive states.
"The most important thing is to understand the ecology of the rat environment: What do they eat regularly, what do they need that they're not able to get all the time?" says Mayer. In the case of New York's subway system, the answer happens to be high-calorie foods. "They love fat. Bobby [Corrigan] uses chicken nuggets in his bait traps, so we know that they love it. Fat will bind certain receptors in their brain that will cause them to eat more fat."
SenesTech is whipping lots of sugar into their bait, too, although they're still wondering whether to blend in two treats favored by laboratory rats, chocolate and peanut butter. ("It's almost impossible to give a rat atherosclerosis," Mayer notes.) The resulting bait comes in two mouth-watering forms, "liquid" and "semisoft."
"The liquid bait looks like milk and tastes like very, very sweet condensed milk," says Mayer who, like a true researcher, has sampled her own supply. "Semisoft bait has more of a waxy consistency to it. It has more oil in it, like a very fat, sweet cream cheese."
THE ONES THAT LIVE MAY HAVE TONS OF FUN
(Shown: A different kind of rat problem.)
Just as all the other weapons New York has hurled at its rats have failed to fell the whiskered menace, the power of chemo-sterilization will no doubt have its limits. That's probably why the city said early on it will use the product as a supplement to other rodent-control tactics, assuming that ContraPest even proves to be effective against the war-scarred NYC rodent.
"I am all about not killing animals; I think we as a race are better than that," says Mayer, who has also worked on chemo-sterilizing rats eating up Asian farmlands and stray dogs overrunning a Navajo Reserve in Arizona. "That's not to say there are not times in wildlife where we have to use a lethal knockdown in the case of infestation or a health problem.... But I believe managing the population to a low level is a better strategy."
And you know what? That wouldn't be so bad for the ones left crawling. Fewer brothers and sisters mean more food resources for the remaining rats, perhaps allowing them to become healthier, more attractive and better able to do what they do best: Get it on. For folks who want to know what that means in the rodent sense, the Rat Fan Club reports the female will perform a mating "dance" by spinning around, stiffly bracing her legs and performing a come-hither vibration of her ears. Her suitor will then bite her on the neck.
They'll be having fun, but perhaps not babies. And that conceivably could be the case in cities across the nation if chemo-sterilization becomes an art form. Mayer says that since the New York subway pilot hit the news, she's been contacted by people in Boston, Chicago and other cities eager to have a chemical potion to shrink their own infestations. They'll have to wait, though, for the scientists to finish their work and shoot for EPA approval.
"I want to complete the research in New York City," Mayer says. "I don't want anybody to get the idea to call me up and get a bottle of the stuff to get rid of their roof rats."
Top image: Brendan McDermid/Reuters