SGARs: Red Death or a Second Silent Spring

“The external world would take care of itself. In the meantime it was folly to grieve, or to think. The prince had provided all the appliances of pleasure…. All these and security were within. Without was the 'Red Death.’” - Edgar Allan Poe

SENSITIVE CONTENT WARNING: This blog contains material and images that graphically illustrate the results of exposure to second-generation anticoagulant rodenticides (SGARs) on individual animals. These images are used with permission from wildlife clinicians. Accordingly, folks who do not wish to see these images are encouraged to view our other content.

I decided to share them because most outcomes of SGAR exposure occur outside the public eye. Animals that succumb to SGAR exposure are often not found. Accordingly, getting accurate data on the problem’s scope is challenging. However, folks need to understand the costs of our decisions to use SGARs in homes and on public property. These images also demonstrate the reality that animal control officers, veterinarians, vet techs, and volunteers face every day because of our toxic relationship with these poisons. It’s one thing to read the testimony of New England Wildlife Center (NEWC) CEO Zak Mertz, who describes treating “hundreds of patients” every year for SGAR poisoning. But it’s another to understand what that means at the individual level.

As I mentioned in my public comments to the Plymouth Select Board meeting, SGARs is an acronym for four active ingredients pest management professionals (PMPs) in Plymouth and elsewhere use to target rats and other rodents: brodifacoum, bromadiolone, difenacoum, and difethialone. As the name suggests, these chemicals impede the blood’s ability to clot by preventing the victim’s body from producing Vitamin K.

When an animal ingests enough of these chemicals, it suffers over several days before succumbing to a lethal bleeding event brought on by a scratch, cough, or sneeze. According to Laura Kiesel at Save Arlington Wildlife, SGARs were developed in the 1970s as chemical successors to first-generation anticoagulant rodenticides (FGARs) such as warfarin, chloropopacinone, and diphacinone.

A barred owl that succumbed to SGAR exposure c/o Jim Joyce.

This begs the question: Why did we need a new generation of anticoagulant rodenticides (ARs)? As Rachel Carson discusses in Silent Spring, animals can evolve to resist chemical threats. This isn’t an alternative for animals like birds of prey, who often take a long time to reach maturity and reproduce relatively slowly. Insects and rodents, however, do not have this problem. Accordingly, rodents were already developing resistance to FGARs by the 1970s. We’re now 50 years on from the initial development of SGARs, so it’s safe to assume that at least some populations of rodents could be developing resistance to this class of ARs as well.

A single dose of SGAR-laden bait is usually enough to kill a rodent. However, it takes days for the rodent to die. During that time, rodents may feed from the bait station multiple times. As a result, their tissues could have levels of SGARs significantly above the lethal dose. This is what makes SGARs a threat to wild and domestic animals, who suffer from ‘secondary exposure’ to the toxins by consuming the dead or dying rodent.

A juvenile red-tailed hawk that succumbed to SGAR exposure c/o Jim Joyce.

While Vitamin K supplements can cure an animal suffering from SGAR exposure, the treatments can last several months, depending on the animal. Moreover, the victim may require infusions of plasma and blood. In one example I’ve mentioned, a great horned owlet brought to NEWC from Barnstable needed extensive care. Here’s an excerpt from Zak’s testimony:

“We spent the next 228 days treating the lone remaining owlet. A normal clotting time for a healthy great horned owl is three to six minutes. This owlet’s blood still had the consistency of water a full 24 hours after the sample was drawn. After six months of daily treatments and supportive care, his blood still took over 30 minutes to clot, leaving him vulnerable to injury. It took 8 months before he returned to normal ranges, and all the while this bird was feeling sick and unable to experience life in the wild. The associated care costs and staff time we invested into his recovery were immense.”

So, Vitamin K is effective over the long term, but it’s not an easy road to recovery for these animals, and many simply do not make it.

A great horned owl that succumbed to SGAR exposure c/o Jim Joyce.

Now that you know what these animals are up against, we need your help! Please consider joining our public kick-off meeting with Mass Audubon at the Plymouth Public Library on 10 April.

If you’re willing, we’d love to have you join our efforts to develop a sustainable solution to this challenge for Plymouth.