Illustration by Murray
Poisons meant for pests are killing animals and impacting humans in Mass
The body was found on a chilly morning in early April 2014, lying under a tree, the legs and feathers stiff with rigor mortis. For four years, Ruby the Red-Tailed hawk was a beloved presence in the Fresh Pond section of Cambridge, where she had shared a nest on the seventh-floor ledge of an office building in the middle of the mall with her long-time mate Buzz. A live camera was even set up to record and broadcast their comings and goings over the years. But now she was suddenly and mysteriously dead, and her many fans were wondering what happened.
Another April morning only one year later, I was emerging from my apartment to travel to a doctor’s appointment when I first saw a man dressed in a khaki coverall uniform placing a large number black metal boxes around the apartment complex. As I approached, he straightened up to face me and I asked what they were for.
“Rats,” he said, placing another one against the backdoor of my own building.
I inquired if there had been any rat sightings in or around the complex recently.
“Not yet,” he replied. “This is just a precaution.”
My town of Arlington had been gearing up for a massive, multi-month reconstruction project on Mass Ave. In anticipation of the rats that businesses and property managers assumed the project would scare out of the sewers and into our residential streets, the bait boxes began to proliferate all over town.
As a former natural resource scientist and conservation biologist, I watched anxiously as I knew what was in these boxes: poison. Not just regular poison, but rather a special kind that doesn’t quickly kill rats or mice, but instead lingers in their system for days or sometimes a week or more. During that time, whatever eats these poisoned rats—whether cats, or coyotes, or raptor species like hawks and owls—can also become poisoned and can die. This is what had claimed the life of Ruby the Red-Tailed Hawk, as a necropsy performed by Tufts Wildlife Clinic in Grafton showed she had suffered a lethal dose of rat poison after eating too many rodents spiked with laced bait.
It does not appear that Ruby was an isolated incident. Impacts of such poisons have hit many other animals and even people, especially children.
Research reveals rat poisons are becoming increasingly commonplace in the bloodstreams of birds of prey in the Bay State. Specifically, another study conducted by Tufts Wildlife Clinic, between 2006 and 2010, found traces of a particular class of “super” poisons—known as Second Generation Anticoagulant Rodenticides, or SGARs—in the liver tissue of up to 86 percent of the Mass-based raptors they tested. In the far reaches of California, rat poison is even killing off threatened bobcat and cougar populations.
Pets can be affected. According to Deputy Director of Advocacy for the Massachusetts Society for the Protection Against Cruelty to Animals Laura Hagen, the MSPCA-Angell veterinary clinic has seen at least 18 cases of suspected or known rodenticide ingestion this year alone.
“The use of rodenticide is especially concerning because it puts both wildlife and companion animals at significant risk of prolonged suffering and death,” Hagen says.
The worst part? Despite this rampant use of rat poison and its unintended repercussions, we are still losing our war against rats.
Soon after the anniversary of those first bait boxes being laid down in my complex, I began to notice others in the summer of 2016.
I was sitting on a bench at Spy Pond Park, only two blocks from my home, when a rat suddenly scurried up to my sandaled foot in broad daylight and cocked its head up at me, as if asking for a treat. He scampered away after I made shoo-ing motions, but over the next several minutes, two more approached me and then began to run around the bench in a frolic. In the four years I had lived here and been a daily visitor to the pond, I never once spotted a rat. Now, I see them frequently and they approach me without any fear. They seem to be as much a part of the ecosystem as the ducks that paddle around. More poison in my town has not seemed to result in less rats.
The same year the rats staked their claim on Spy Pond, over in Boston proper, the city’s Inspectional Services Department logged more than 3,500 rodent-related complaints in the city—a startling 30 percent increase from the preceding two years. In July 2017, Governing magazine placed Boston as number two in the nation for rat sightings and complaints, surpassed only by Philadelphia. Many people have scrambled to identify some of the causes in increased rat activity, which range from warmer winters due to climate change, to less exposure to predators, to more population density (more people equals more trash), to increases in development and construction projects. However, some have also posited that the widespread use of poisons may in fact be a contributing factor to exploding rat populations in Boston and beyond.
In a feature article on rats published in Boston Magazine earlier this year, the word poison was used multiple times to describe the efforts of Boston officials to manage rats, including phrases such as “buckets of poison,” “a paint bucket full of rat poison,” and “a truck full of poison.” But nowhere in the article are these poisons identified. Nor is there an explanation of how they work, or of their history in the United States.
Most poisons in bait boxes are of the same class that killed Ruby the Red-Tailed Hawk—SGARs that include brodifacoum, bromadiolone, difethialone, and difenacoum. These poisons work by interfering with the blood-clotting process in whomever or whatever ingests them, resulting in internal hemorrhaging that can be fatal. Animals with dangerous levels of the poison have been found bleeding from the nose, eyes, and mouth, as well as from open wounds.
These poisons, however ironically, may be doing a better job at wiping out some of the most effective predators of rats, while the rats themselves manage to keep rebounding. Experts note that this may be because rats are such rampant breeders—they tend to mate and can even breed year-round, while a single pair of rats can give birth to up to 2,000 babies annually (some estimates even go much higher). By contrast, raptors, like hawks, eagles, and owls, are seasonal breeders who only lay eggs for two to four chicks every spring on average. Simply put, rats outbreed the poison, with the constant presence of bait luring new populations once preceding ones have been eradicated.
“[It] is wasteful and tragic to kill off the best natural solution to controlling rats that we have,” says Lisa Owens-Viani, president and founder of the California-based nonprofit project Raptors Are the Solutions (or “RATS”), which was established to educate people about the ecological role raptors play in urban and suburban environments and how they are adversely affected by the widespread use of rat poisons.
In particular, Owens-Viani points to a recent scientific study based in Ventura County, California that found that local hawks and owls were nearly 50 percent more successful in reducing burrowing damage caused by resident rodents as compared to anticoagulant bait stations used at a control site. She also criticizes poisoned bait as perpetuating the infestations they are supposedly designed to deter.
“When you think about the word ‘bait,’ it literally means you are baiting [the rats] into an area and they’re going to keep coming back as long as bait keeps getting put out,” says Owens-Viana, whose RATS project recently established a Massachusetts chapter.
Non-target animals like wildlife and pets aren’t the only victims of the rat poison.
In 2008, the US Environmental Protection Agency announced it would begin phasing out the availability of over-the-counter SGARs over a three-year period. The American Legislative Exchange Council (ALEC) and the manufacturer of the popular over-the-counter SGAR product D-Con, Reckitt Benckiser, balked at the newly proposed restrictions and a lengthy legal battle ensued. They resisted despite reports revealing that more than 10,000 children were accidentally eating SGAR poisons sold over-the-counter annually. Furthermore, the poisonings were disproportionately impacting low income children of color ages four and under. In one case in 2015, 19 inmates at Rikers Island Correctional Facility in New York were sickened due to eating meatloaf that had somehow been tainted with SGARs.
In 2014, Reckitt Benckiser finally agreed to stop producing 12 of its SGAR-based D-Con items. However, the new EPA guidelines still allow licensed pest control operators to market and use the poison in so-called “tamper-resistant” bait stations, while some pre-existing inventories of now-banned D-Con products can occasionally be found on store shelves. Moreover, the new bait stations are sometimes heavily marketed by some exterminators to their consumers, most of whom are not likely aware of their extensive environmental and public health risks.
In the absence of natural predators, many cities and towns are trying to find out what else can be done to control rats that doesn’t include poison. Locally, from 2014 through 2016, the City of Somerville partnered with the corporation Senestech to use a non-lethal bait the latter had developed called ContraPest. As its name suggests, ContraPest significantly lowers the fertility rates of both male and female rats, cutting down on their overall populations. Unlike poisons, the ContraPest bait is quickly metabolized by rats (within minutes of ingestion) and is not stored in their fatty or organ tissue—meaning it does not work its way into the food chain like poisons do. According to Denise Taylor, spokesperson for city of Somerville, pilot studies they conducted found that rodent population growth was suppressed by 57 percent and 67 percent at ContraPest test sites at Trum Field and Gilman Street, respectively.
In addition to ContraPest, Somerville provided new “rodent-resistant” 64-gallon trash carts to every resident in the city free of charge in June 2014. These carts come equipped with secure lids and are made of sturdier material that can better keep rats from accessing the trash inside of them, while also being less prone to blowing over in the wind. The city also implemented rigorous dumpster licensing and inspections guidelines—increasing the number of licensed dumpsters from 177 to 622 in order to ensure they are clean of outside debris and food waste, free of holes and have suitable, tight-fitting lids. In the first 18 months of spearheading this expansive effort, Somerville experienced a 36 percent decrease in rat sightings.
Taylor explains that using Integrated Pest Management (IPM) techniques that include an array of methods, ranging from better trash management to public education initiatives and innovative technologies like ContraPest, offer the best chance at success in controlling rats.
“All of these approaches work in tandem and are needed,” says Taylor. “But we did observe our most significant declines in rodent activity after the simultaneous introduction of the city-issued trash toters with accompanying public outreach and the intensified dumpster registration and inspection program which fits with a key approach to successful rodent control: restricting access to food and water sources.”
Currently, Somerville is no longer using ContraPest—which cost $70,000 to test pilot. While Somerville still uses some SGARs to bait sewers in areas of suspected rodent activity, they’re instead refocusing their program on preventative measures and exclusion. They’re also looking into using dry ice to eradicate specific rat nests and burrows they identify—that is, now that it looks like dry ice is a feasible option.
In 2016, Boston and several other cities across the US made headlines for using dry ice for rat control—even as it was not formally registered as a rodenticide with the federal government. As a result of this public revelation, the EPA ordered that municipalities stop using it immediately.
By the end of June 2017, Bell Laboratories was granted federal registration of their dry ice product as a rodenticide (aptly known as “Rat Ice”), meaning it can now be legally used to exterminate rats across the US pending state registration and municipal-level approval. Currently, its availability is limited to a handful of major cities, including Boston, though that will likely be quickly expanding in the near future.
Dry ice works to eliminate rat nests by releasing a deadly amount of carbon dioxide fumes into their burrows as the ice melts. Unlike baits with poison or ContraPest, dry ice depends on a more targeted approach, and must be stuffed into confirmed rat burrows that occur only in outdoor settings (dry ice usually can’t be used inside structural dwellings because the CO2 fumes can potentially harm humans).
The extent to which alternatives like dry ice and ContraPest, or more comprehensive plans that utilize IPM methods like better trash management, will replace poisons is unknown. To that end, I’ve taken the liberty as a concerned citizen to file a draft of a bill that would establish an independent commission that would investigate the wider impacts of SGARs on our natural environment and public health and explore alternative solutions. State Rep. Sean Garballey (D – Arlington) will file it this year.
In the meantime, co-founder of Senestech, Dr. Loretta Mayer, notes that while some newer methods might have larger upfront costs, they can offer lasting benefits in the long term. Overall, she believes that striking a balance between different rodent management methods is key to regaining control over rat populations.
“Rats have been a problem for centuries,” Mayer says. “We all need to listen to one another and work together and with wildlife conservation in mind to make certain well-planned and cautious steps to succeed.”