A plague of frogs? Big hatch is 'unprecedented'


A NORTHERN LEOPARD frog. Photo by Jim Andrews

ON JULY 12, portions of Creek Road in Salisbury were plastered with dead Northern Leopard Frogs. Photo by Jim Andrews
This was unprecedented in all of my field work. It seemed like it was biblical in proportion. If they were falling from the sky, it would have been a plague. — Craig Zondag

SALISBURY — Since early July, Vermont State Herpetologist Jim Andrews’ inbox has been flooded with emails, phone calls and reports of what some Addison County residents are calling “Frog-ageddon.”

According to Andrews, thousands of frogs have recently appeared along the Otter Creek floodplains of Cornwall, Leicester and Salisbury.

“Landowners report not wanting to mow their lawns, pool owners have reported hundreds of small frogs in their pools and drivers report the tremendous carnage on the road surface,” wrote Andrews in an email to the Addison Independent on July 12.

Determined to see the carnage for himself, Andrews visited Creek Road in Salisbury the same day, where he found it “covered with the bones, fluids and bodies of dead Northern Leopard Frogs. The tire tread areas of the road,” he added, “are covered with a solid black surface of frog bodily fluids. I estimated about 100 dead frogs per square yard of road surface.”

According to Andrews, Northern Leopard frogs are “unusual” in the vicinity of the Cornwall Swamp. “They thrive primarily in the Lake Champlain Basin, where there is a combination of permanent water, adjacent floodplains and nearby fields,” he said.

The frogs overwinter underwater, he explained, which means that these frogs likely spent the colder months in Otter Creek and the larger ditches that drain into it. “In the early spring, they travel out into the shallow and warmer waters of the flooded fields, backwaters and ditches along the creek, where they lay egg masses of 1,000 eggs or more per mass.”

Andrew noted that in most years the surrounding fields and ditches would drain or dry out before the Leopard Frog tadpoles were ready to leave their aquatic homes. “This year, due to our increased rainfall, that was not the case.”

Craig Zondag, the Lemon Fair Insect Control District’s field coordinator-biologist said he has never seen a hatch of Northern Leopard frogs like this one in his 11 years of observing the Cornwall Swamp, whose floodplain, he said, was inundated with water for the better part of two and a half months this spring, creating excellent breeding habitat for the frogs.

He recalled one day last week where, as he approached one of his data collection sites in the vicinity of Creek Road, it “looked like popcorn was bouncing off the road, with thousands of frogs waiting on the sides to move en masse.”

According to Zondag, Northern Leopard Frogs have been known to hop as far as four to five miles in search of a new water source. “They have tremendous mobility and endurance,” he says. “It makes me wonder if all those frogs survived, how that would play out in the broader ecosystem.”

Preston Turner lives about a mile east of Swamp Road in Salisbury. He says the number of frogs has declined over the past week on Swamp Road, but that he’s now seeing them in his yard. “They are constantly hopping every which way and I’m kind of anxious to mow the lawn,” he reported. “Just last night, it was a bit disturbing driving home. You feel like you can’t avoid them.”

Robin Callahan, administrative assistant at Salisbury’s Shard Villa reported finding hundreds upon hundreds of Northern Leopard Frogs stuck in a concrete basin on the senior living facility’s property over the past few weeks. “We have all been trying to collect these things and get them out of there. Our grounds and maintenance guy had to go down twice and use buckets to scoop hundreds out at a time,” says Callahan. “It was like a mini-invasion.”

On July 3, one household in the vicinity of Brandon and Salisbury posted a humorous cardboard sign on their lawn that read “Free Frogs.” Still another resident of Swamp Road described hearing “car tires just ringing with the popping of frogs” from his porch in the evenings. He has been making a long detour around Swamp Road to run his errands for the past week or so to avoid adding to the road kill.

One might ask if the unusually wet weather is the trigger, why are other frog species not also hatching all at once?

Andrews has an answer. “This is the only species of frog that uses this combination of habitat types and, consequently, is the only species emerging in these huge numbers.”

JAN KENNEY FILMED the frogs swarming her garage and front porch in Salisbury recently. "The popping noise is someone inadvertently stepping on one," she said. 

Video courtesy of Jan Kenney

He expects residents will find Northern Leopard Frogs in large concentrations this year in other flood lands along larger rivers in the Lake Champlain Basin, where fish, herons, crows, gulls, hawks, raccoons, snakes and other predators and scavengers will enjoy “an abundant food supply.”

Andrews also speculates that hatches like this could happen in the future. “I suspect that these unusually high numbers are the result of the increasing amount of rainfall that we have been receiving, not just this year, but for the past decade.”  

Zondag says it is too soon to tell if the massive frog hatch will have any bearing on mosquito populations in the area. However, one local species will be pleased: the Culex perritans, a sucker that prefers the soft tissue of amphibians and snakes to that of mammals and doesn’t typically prey on humans.

As of Friday, July 19, Zondag reported that the frogs appear to have started their migration upland. “I had to shuffle my feet to walk across a field above the swamp on Thursday evening, as it was carpeted in frogs,” said Zondag, adding that they were prevalent throughout the woods above Route 30 and less prevalent on Creek and Swamp Roads than on past evenings.

Still, the abundance of frogs along the Otter Creek has certainly been memorable.

“This was unprecedented in all of my field work,” said Zondag. “It seemed like it was biblical in proportion. If they were falling from the sky, it would have been a plague.”

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