There's concern growing in Arlington, Massachusetts, where residents fear a family of owls died in a park from rat poisoning.
A memorial sits at Menotomy Park for the Great Horned owl mother and her two owlets after their "devastating" deaths.
"They had a nest in a tree right over here, and I think we just felt so lucky that we had this here in our neighborhood and that they chose to build their nest there and live amongst us," one woman told NBC10 Boston.
"We're really sad because it was just an exciting, special thing to be able to see the whole life cycle of the owls," another woman shared.
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Officials say the owls were never sent for testing, so there's no way to know if they died of rat poisoning, but residents in the area say they're concerned.
"The poison we're talking about here is called second generation anti-coagulant rodenticides. You'll hear it referred to as SGARS for short. What this poison is, it's an anti-coagulant, and what that does is it's stops the blood from clotting," said Zak Mertz.
Mertz, who is with the New England Wildlife Centers, says they see about 100-200 cases like this every year in Massachusetts -- where predatory animals like an owl or fox eat a rodent that's been poisoned, and then those animals get sick, as well.
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"A lot of times these animals come in and they've been repeatedly dosed with these SGARS with catastrophic results," Mertz said.
In turn, Mertz says it ends up only making the rat problem even worse.
"If you accidentally poison a great horned owl that was going to eat a thousand mice that year, not only have you destroyed nature's natural predator control, but you've probably increased the mouse population at the same time," he explained.
Which is why education is key, Mertz stresses, so that consumers can look for safer alternatives.
There's a bill in Massachusetts to try to raise awareness on the issue that, if passed, would in part require pesticide companies to disclose information about its potential effects on the environment.