Endangered Ontario: Fouled marshes and the Fowler’s toad

Invasive reeds are taking over Ontario’s wetlands — and squeezing out one of the province’s rarest amphibians
By Tim Alamenciak - Published on August 14, 2017

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The sweet song of the Fowler’s toad fills the night air in mating season. It’s a veritable symphony of high-pitched screams, loud and sharp, in contrast to the ribbit of its American bullfrog brethren.

But a terrible invader bent on taking over Ontario’s wetlands threatens to silence that beautiful chorus for good. Phragmites australis, a pesky reed, has spread quickly through the province, forming dense thickets that can grow 10 feet tall and crowd out native vegetation.

In doing so, the reed denies Fowler’s toads access to the shallow pools of water where they breed and raise their young.

“Over the past 15 years, this invasive reed has come in and taken over the marshes,” says David Green, a professor at McGill University and the president of the Herpetologists’ League, an international organization dedicated to the study of amphibians and reptiles. “Coincident with the expansion of this reed and the filling-in of virtually all the shallow wetland close to the dunes, the Fowler’s toad started to decline and they went down and down.”

Green has spent his career studying the Fowler’s toad (named in honour of Samuel Page Fowler, a 19th-century naturalist) and has been experimenting with artificial breeding ponds to bolster the dwindling populations.

“Some toads did find them,” Green says. “We also used them to raise tadpoles that we had rescued from beach pools that the animals had used in desperation.”

The toads live along the north shores of Lake Erie, at Long Point, in Rondeau Provincial Park, and along the Niagara Peninsula. They inhabit sandy dunes by the water but escape to the marsh to breed.


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The Ministry of Natural Resources and Forestry is able to monitor the populations closely because they’re so small, and because one of them is located in a provincial park. But monitoring isn’t enough to save the toads from a catastrophic weather event.

“Because they’re limited to these small sites, some sort of freak event could have a very severe impact on the population. A severe winter or a significant storm that washes the beach away could happen,” says Joe Crowley, a species-at-risk specialist with the MNRF. “Even in Rondeau, where we can do a pretty good job of protecting the species, if the beach washes away, there’s not a lot we can do.”

There is one weather event that could actually be good for the toads. Natural water-level fluctuations and battering winds occasionally lead to “dune blowouts,” which create depressions in the sand that water can flow into. Fowler’s toad populations tend to boom after blowouts since the events cause breeding ponds to proliferate.

“I'm talking to the Canadian Wildlife Service about what we can do to refurbish these ponds,” says Green. “Although the rate things are going at Long Point right now, we may not have to — because the lake may just blow in the dunes and do it itself.”

Green, who’s been observing Fowler’s toads for more than 30 years, is optimistic they can recover — but threats to the species’ survival are not static. Reeds are spreading rapidly across the province. Some have called them Ontario’s worst invasive plant. And with time, they grow denser and more resistant to removal.

Development is increasingly a threat, too. “The animals themselves are really good at weathering any kinds of storms that the lakes throw at them,” Green says. “But they can't deal with break-walls and sand getting taken away and vehicles driving on beaches and invasive plants covering the dunes or marshes.”

Video by Matthew O'Mara

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