Bald eagles have made an impressive comeback in recent decades, returning to parts of New England from which the majestic birds had disappeared in the 20th century due to pollution and habitat loss. But this Independence Day, America’s national symbol — along with several other predators — faces a newer threat.
Call it the law of unintended pest-control consequences. Some decades back, a new generation of rodent poisons was developed to target rats and mice.
The new toxins, called Second Generation Anticoagulant Rodenticides, or SGARs, do their deadly work by preventing the normal clotting of blood and generating hemorrhaging, thereby causing the poisoned rodent to bleed out.
But that doesn’t happen instantly. Instead, the rodents grow increasingly dazed and sluggish after emerging from the bait boxes where they ingest the poison. It can take a week or so for them to die, during which time they are easy targets for eagles, owls, foxes, bobcats, and other animals that consider rodents fine dining. The SGARs then bioaccumulate in those animals, sometimes killing them as well.
“By the time a bird gets a rat, it is like a toxic bomb,” said Laura Kiesel, an activist and writer with an academic background in wildlife biology, who is leading a campaign to ban SGARs in Arlington.
SGARs poisoning has killed two eagles — an adult female and her fledgling — in Arlington in the last two years. Arlington has also lost a family of great horned owls that displayed the telltale signs of SGARs poisoning: thin, watery, bright-red blood running from their bodies even after death. Testing showed another great horned owl death was definitely from SGARs.
Waltham has also had a SGARs-caused eagle death, while an eagle in the Hartford area also perished from SGARs poisoning recently. California has found the rat poison responsible for the deaths of bobcats and a mountain lion.
Zak Mertz, executive director of the New England Wildlife Centers, and Priya Patel, its medical director, told the Globe editorial board that their two nonprofit animal hospitals treat scores of animals each year that display signs of SGARs poisoning, which often include bleeding from all orifices.
“It can be just heartbreaking to see the way they are struggling because of it,” said Mertz. It took a great horned owl some 250 days to recover sufficiently enough to be released back into the wild, noted Patel.
Solutions here are hard, because they pit the need for rodent control against the health of nontarget animals. No one wants to see more rats, though according to Kiesel, there aren’t studies that show a correlation between the use of SGARs and a reduction in the rat population. The federal Environmental Protection Agency is considering further SGARs regulations, including whether to restrict their use in important habitats for endangered species.
Mertz said he hopes that SGARs can at least be moved to the back of the rodent-battling toolbox. Certainly pest-control companies should be encouraged to highlight other methods to control rat populations.
There are other rat toxins that don’t travel up the food chain, according to experts. And there are other approaches worth trying. For example, dry ice, which produces carbon dioxide, can be used to fumigate rat burrows in some circumstances. Rat contraceptive chemicals also show promise.
But many of those methods require more regular application or monitoring and thus would hike costs, noted David Flynn, president of the New England Pest Management Association.
The eagle and owl deaths have sparked an effort in Arlington to ban SGARs, which are sold only in commercial-size quantities not intended for individual homeowners. Arlington has banned the use of SGARs on municipal land. But because the state has already established a body of law and regulation around pesticides and rodenticides, municipalities need legislative permission before they go further. Thus Arlington’s lawmakers have filed home rule petition to give their town that ability.
“I am not pro-rat,” Representative Sean Garballey, Democrat of Arlington, is quick to stipulate. (Who, after all, would want that label?) “But what I am for is protecting these awesome birds of prey.”
There’s a strong case to be made for giving Arlington that authority, since several local features, such as its proximity to the Mystic River and Mystic Lakes, as well as its green spaces and wetlands, have obviously made it a particularly susceptible spot for SGARs to migrate up the food chain into the raptor population.
Meanwhile, a bill sponsored by Representative James Hawkins, Democrat of Attleboro, calls for requiring pest-control companies to file digital, rather than paper, reports specifying where they are using the second-generation anticoagulants, which would make it easier for researchers to compare their use with the deaths of owls and eagles, as well as other rat predators.
Everyday citizens can help by doing simple things, said Hawkins, who named a few: plug holes in foundations; eliminate brush piles; make sure there is nothing a rat would consider tasty, including garbage or birdseed or chicken feed, accessible to rodents. Newton, meanwhile, recommends that residents ensure that garbage bins are tightly sealed and that outdoor grills are clean of leftover barbecue.
Another method: Welcoming owls to the neighborhood with elevated owl-box homes.
Which is where a certain conundrum enters the equation. Given that a single owl can kill upward of 1,000 rodents a year, when owls succumb to SGARs poisoning, a hyper-effective natural pest-control predator is eliminated along with the rats.
In general, state government should take the lead in evaluating, regulating, and banning SGARs. Hawkins’s legislation is a good first step, one that should produce valuable information — information that might support a statewide ban.
Editorials represent the views of the Boston Globe Editorial Board. Follow us @GlobeOpinion.