Acadia researchers find N.S. coyotes have elevated mercury levels

A new study of coyotes by Acadia University researchers to monitor mercury concentration in Nova Scotia's land-based wildlife has revealed elevated levels in the predatory animals.

A research team from the university in Wolfville, N.S., studied the livers of 101 coyotes provided by the Department of Natural Resources from around the province and found mercury levels higher than those recorded in most other land mammals in North America and Europe.

Biology professor and lead researcher Mark Mallory said that while the specific levels themselves are below the range reported to cause adverse effects in animals, it remains a concern to him.

"I'm always a bit concerned that there's contaminants of any form, whether it's organic contaminants, herbicides, pesticides, in this case mercury. You know, the fact that this is in our wildlife is always something that's a bit alarming," said Mallory, a Canada Research Chair in Coastal Wetland Ecosystems.

Globally, activities such as burning fossil fuels, gold mining and metal and cement production account for the bulk of human-caused atmospheric mercury emissions.

Mercury concentrations have increased in the atmosphere over the past two centuries, the study notes, and southeastern Canada and the northeastern United States have been identified as mercury "exposure hotspots" because of prevailing winds carrying emissions from industrial areas of eastern North America.

The researchers chose the eastern coyote for their study because it's a top predator in Nova Scotia and samples were readily available because of the province's active trapping program to manage numbers. They analyzed the coyotes' livers because it's the organ where an accumulation of compounds like mercury can be found.

Considerable research has been undertaken in aquatic and coastal ecosystems in the province, says the study, which was published this month in the journal Science of the Total Environment. But there is an "information gap" about mercury concentrations in land-based animals like coyotes.

"We have lots of good information that's been developed in aquatic systems and not so much in terrestrial systems," said Nelson O'Driscoll, who works in Acadia's earth and environmental science department.

'Walking garbage cans'

The researchers found that coyotes collected from southwest Nova Scotia had higher levels of mercury than those from other areas of the province, which was consistent with findings in previous studies on birds, fish and lichen.

But Mallory said it's difficult to establish obvious patterns because coyotes are "walking garbage cans" and consume a variety of different things.

"You could have coyotes that are eating mostly vegetation and insects right next to ones that are hunting deer right next to ones that could be scavenging human food," he said. "So their exposure to mercury, I think, is all over the place."

The study found wide variations in mercury concentration in the samples that contradicted what the researchers had expected they would see based on the age and sex of the coyotes. For instance, some juvenile coyotes had higher levels of mercury than adults.

Because of those variations, the researchers concluded coyotes are not as well suited as a biological monitoring species as they had hoped. But their work has sparked ideas for their next steps.

"I'd love to do the exact same thing with another species," Mallory said. "Something ideal would be something like a snowshoe hare or a vole, something that we know coyotes eat and to see whether we get the same pattern." 

Mallory said they also want to study a wildlife species, like fishers, that has a more restricted diet than a coyote.