Could rat birth control work in Ottawa?

For rats in Ottawa's Heron Park neighbourhood, Melanie Giroux has become something like the Grim Reaper.

Giroux estimates she's trapped and killed many hundreds of the rodents since her backyard became infested in 2021. That year alone, she bagged nearly 500 using black reusable traps.

Despite that prolific record, Giroux said it hasn't gotten any easier.

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"You get the heebie-jeebies basically every time you have to deal with putting one in a bag and disposing of it," she said.

Now the City of Ottawa, faced with a rise in the number of rat-related complaints, is looking to move beyond poison and traps to consider what it sees as a more humane alternative: birth control.

Last week, city council directed staff to write to Health Canada's pest management regulatory agency asking it to consider legalizing humane rat fertility reduction bait.

'The pressure is on'

In 2023, the city responded to nearly 750 rat-related calls, prompting the creation of a "rat mitigation working group."

The challenge for cities and their human residents is that rats multiply quickly. Rat moms give birth to about eight babies per litter. After three to four weeks, both the babies and their mother are ready to breed again, meaning one female could generate 15,000 descendants in a single year.

That's one of the reasons why College ward Coun. Laine Johnson has pitched the idea of putting Ottawa's rats on birth control.

"Cities are being asked to build more than ever before," Johnson told CBC. "And with that, we are disrupting rat habitats."

With ongoing LRT-related construction, residents are seeing more rats than ever before — and they're demanding a solution.

"The pressure is on," Johnson said.

Giroux's rat infestation started in 2021, during work to extend the nearby Trillium Line in Ottawa's south end. She believes the LRT construction disrupted the rats' habitat and they fled to a dumpster located near her backyard fence.

"If no one eliminates them, they are going to keep reproducing and we are going to get another boom," she told CBC.

But the push to legalize the birth reduction bait could take time. The approval process alone, which includes a complete scientific review of the product, could take up to two years, according to Health Canada.

The federal agency told CBC only one product for animal contraception is currently approved in Canada. Ovocontrol, approved in 2017 and used as a bait to limit the hatching of pigeon eggs, has been in used in Toronto for a year now.

How the contraceptive works

The contraceptive Ottawa is looking into is called Evolve soft bait. The active ingredient — cottonseed oil — is supposed to interfere with the reproductive systems of both male and female rats.

There are some concerns, including what happens to dogs or squirrels that consume the bait. The company behind the product, Senestech, says it could make pets temporarily infertile if they consume large amounts over an extended period, but it won't kill other species.

Loretta Mayer, the scientist behind the formula for the first-ever rat contraceptive, said baited poisons and traps don't really work because they don't get all the rats.

"The ones you don't get reproduce," she explained. "So the root cause is reproduction."

Mayer, who worked for Senestech, said the rodent contraceptives have been used in several major U.S cities including Boston, Washington D.C, San Francisco and Chicago.

"We're now looking to present our final data which is showing in a mixed neighbourhood that is open population reductions that range from 80 per cent, but to a sustained 50 per cent throughout a neighbourhood," she explained.

Mayer spoke to CBC from New York where she was working to help manage that city's infamously rampant rat population through contraceptives. New York City proposed the pilot project after Flaco, an owl that escaped the Central Park Zoo, died in part from ingesting rat poison.

Birth control isn't the sole solution

New York has tried to sterilize its rats before, but previous attempts have failed.

According to Kaylee Byers, an assistant professor in the Faculty of Health Sciences at Simon Fraser University, contraception should only be used alongside other measures to control rat populations, such as improving garbage storage and pickup.

She said New York has failed to control its rat population because its streets are still littered with food sources for the rodents.

"The more food you have, the more rats can survive, so you really have to address aspects of waste management," she told CBC.

Giroux doesn't know if birth control is the answer to her backyard infestation, but she's certain she can't wait years for a solution.

"They just need to find some way to remediate this problem now," she pleaded. "For those of us stuck dealing with the rat issue."