Frog hunting 101: How one man is trying to eradicate an invasive species
Indiscriminate and voracious, American bullfrogs can eat local species to extinction
Conditions must be just right for hunting frogs. It can’t be raining—this summer’s wet start was a serious impediment—and it has to be dark, a logistical irritant at our latitude.
It all has to happen within the months between the time the frogs wake up and, ideally, before the females lay their thousands of eggs.
There is one person in Greater Victoria who has accepted the job as his personal mission: Stan Orchard.
“I’d hate to be doing anything else,” he told me on a summer night after dark.
He was perched at the back of an inflatable boat, floodlight in one hand and his patented elecro-frogger under the other arm. I was balanced on the gunwale with a camera and (useless in the dark) a notebook, while a member of Orchard’s summer crew rowed us in meandering circles around a pond in Metchosin.
It’s not that he loves spending every clear evening between April and October catching frogs, but he knows that if he doesn’t there’s no one else who will stop them from spreading into Victoria’s watershed and beyond, to the rest of Vancouver Island.
Since they were first spotted on the Island 30 years ago, American bullfrogs have conquered the Saanich peninsula. Orchard calls it an “unmanaged population.”
They reproduce alarmingly efficiently. A female bullfrog lays around 20,000 eggs each year, and about 10% will survive past metamorphosing from tadpoles to frogs. That indicates how high mortality rates are in the ecosystems where bullfrogs evolved. Here, with minimal predators, it means each adult female can add 2,000 new frogs to the system every year.
As far as we know, the omnivorous amphibians have not crossed to the Westshore from the Saanich Peninsula. Orchard has drawn a line from Finlayson Arm at Goldstream Park down to the Esquimalt Lagoon: that isthmus, a corridor that includes Langford Lake, Glen Lake, and the Humpback Reservoir, is his strategic battle line.
Every year new waves of frogs come westward.
In the 15 years Orchard has been working to control their spread he guesses he’s captured 70,000 of them. Only two, to his knowledge, have made it as far west as the Humpback Reservoir in Langford. That reservoir is no longer Victoria’s drinking water source, but the watershed beside it is.
“Do you really want millions of bullfrogs in the drinking water for Victoria?” he asked the Capital Regional District back in 2007. “Bullfrogs are not just in the habitat, they actually become habitat for parasites and pathogenic viruses and bacteria.”
They’re an asymptomatic carrier of two viruses that drive native frogs to extinction—that was part of the reason behind the CRD’s decision to fund his project. They also have insatiable appetites for anything that can fit in their mouths, including several at-risk species—and baby ducks.
“Bullfrogs swallow baby ducks alive and dissolve them in hydrochloric acid and proteolytic enzymes,” he said. All that’s left by the time a biologist like Orchard opens the stomach are two little webbed feet.
Despite the trouble they bring to ecosystems and directly to humans, catching the frogs isn’t the hard part. The hard part is convincing people they need to be caught.
Frog hunting 101
Back in June I met Orchard at 9:20pm on a side road in Metchosin. He led the way into a private farm containing a large pond. Tall grass and some leggy trees surrounded the pond, with hay fields on the far side
He and his crew mate for the night hauled out their gear: an inflatable dinghy and air pump, a long pole with a net at one end, a flood light, a waterproof battery, a five-gallon bucket, ice, oars, and hip waders.
Daylight seemed to leach into the dark pond as a piercing whine from the boat’s air pump filled the night. It was three times as loud as it should have been, because the correct adaptor was missing; Orchard held the hose in just the right way to get enough air into the boat, but puzzled at where the piece could be. Extra levels of rain in the first half of the summer meant frog hunting trips were infrequent. He couldn’t recall who from his crew of six had had this kit out last. The job is a chance for science students to get some field experience, and the American bullfrog’s schedule suits university summer breaks.
By the time Orchard slides the boat into the pond, it’s full dark and the three of us are awkwardly balanced. The inflatable seat couldn’t be filled without the adaptor, but frogs don’t care about that, so we set out.
We begin a slow perimeter route of the pond, Jon Park maneuvering through thick patches of lily pads in a boat that’s overful and underinflated. We’re quiet. Orchard has the floodlight, one of two key implements for frog catching, positioned dead ahead.
At the right angle, the light catches a frog’s eyes like a deer. They’re smaller though, about the size of a raindrop. Which is exactly why you can’t frog hunt if it’s recently rained: every raindrop looks like a frog in the dark.
“There’s one,” Orchard says, pointing with his pole for Park to navigate us forward.
The pole Orchard has designed has a small net on the end, and an electrified metal hoop behind it. When he turns it on, the electric current stuns anything within a small radius. I can’t see a thing, but Orchard jabs his pole into the water, clicks the button to set off the electric jolt, and quick as a jig we’ve caught a frog.
When stunned, an American bullfrog’s back legs shoot out ruler-straight. The movement involuntarily propels them forward, so if Orchard positions his pole properly, they stun-jump right into the net.
He moves the net around to the side of the boat where Park confirms it’s the right species, then scoops the hapless frog into the waiting bucket, filled with a few inches of pond water. The frog will recover its senses in a minute, so he pops the lid on before continuing to circumnavigate the pond. If they accidentally stun something other than a bullfrog, it’ll be paralyzed for a moment and quickly recover with no harm done.
Later, Orchard and Park will put the bullfrogs in cold storage just above freezing. The frogs naturally enter a cold-induced stupor, how they normally survive the winter. Then they go into a deep freeze to die peacefully and without chemicals. The bodies can be mixed into compost or animal feed.
It’s an odd way to spend a Thursday night, and Orchard admits there are other things he would like to do. But if he were home, he’d be thinking about the frogs hopping beyond his battle line to colonize the Island. That, he can’t abide.
Invasive, voracious omnivores
American bullfrogs don’t belong on Vancouver Island. They have no natural predators here, and are themselves formidable predators—not for their hunting prowess, but for their lack of discrimination.
American bullfrogs will eat anything.
A decade ago, Orchard examined the stomach contents of over 5,000 of them where he found bats, a juvenile muskrat, and hummingbirds. Of course, a lot of insects: dragonflies, butterflies, beetles, and wasps. The sting of a wasp did not seem to deter the frogs, nor did spikey ridges on stickleback fish. He found frogs—including American bullfrog tadpoles—snakes, Western painted turtles, shrews, voles, and Coho salmon. In total Orchard counted 15 distinct classes of organisms.
“There's almost no other species with anything remotely like that kind of an ecological footprint,” he said. “If it'll fit in the bullfrog’s mouth, it'll turn up in a bullfrog’s stomach.”
The only species that eats as widely and indiscriminately as the bullfrog is humans, he told me.
Orchard became the de facto American bullfrog expert in the late 1980s when he was working at the Royal BC Museum as the herpetology expert—that is, frogs and amphibians. People reported a mass of these alien-looking tadpoles in the warm swimming waters of Beaver Lake.
They had bodies the size of golfballs and disproportionately small tails. Fishermen thought they could make good bait, and kids liked playing with the creatures.
Unfortunately, bullfrog tadpoles make terrible fish bait. As a defence mechanism they collect extra alkalis in their skin which make them taste awful.
Three people admitted they were part of the genesis of the local frog invasion: Two farmers who thought, not uncommonly, they could farm the frogs in a backyard pond and harvest their legs as a source of protein; and one young boy whose parents let him bring a bucket of these alien tadpoles home to Saanich from the mainland and release them in Elk Lake.
The legs were a popular source of protein during the Depression, and their foothold in the Lower Mainland possibly began then. People have appreciated the frogs as pets, food, and novelty for years before they gained critical mass on the Saanich Peninsula.
Orchard’s first concern when he saw the swarms of tadpoles at Beaver Lake’s swimming beach was for the native frog and reptile species. Bullfrogs could eat or infect them to local extinction if given a chance.
“That is not a compelling argument to a lot of people who say, when you tell them, ‘They'll drive at least two species of aquatic foraging garter snakes to local extinction.’ They'll consider that a public service,” he said. Then he tells them about the baby ducks eaten alive, and how all that’s left are the two little webbed feet—”That has an impact on people.”
Western painted turtles are an at-risk species, with conservation programs in place to protect their habitat. But Orchard says their most powerful threat are bullfrogs. In the first few days of May when turtle hatchlings leave their nest and make their way to the water, he’s caught a dozen frogs with stomachs full of the hatchlings. The next night there will be a few more, but then it’s over. That’s the end of the turtle’s hatching season, and the bullfrogs have gotten them all.
“If you're not managing bullfrogs, you're not managing painted turtles at all,” he said.
It’s hard to say how much a bullfrog eats, because it varies based on age and time of year. They are seasonal, opportunistic eaters. In June when tree frogs are hatching, you can find a bullfrog stomach full of tree frog tadpoles. And by August when they’ve metamorphosed into frogs, a bullfrog stomach will be stuffed with juveniles.
And, bullfrogs can travel a sizable distance. An adult can migrate five to 19 kilometres per year. Since juveniles are seen as food by their elders, they have good incentive to travel.
Orchard’s patrol line between Langford and Colwood is funded by the CRD Integrated Watershed Services and CRD Regional Parks, and he takes on some side projects, like one in Metchosin. That frog population is almost under control after less than 10 years of hunting. He believes it was an isolated population rather than an expansion from the peninsula.
It’s a good sign that Orchard’s team has been able to stave off expansion to the watershed and beyond, but the kicker is he’ll never be out of a job unless he can eradicate the whole population on the peninsula.
The CRD has identified bullfrogs as a threat to the watershed, and fund Orchard enough to monitor that corridor between north Langford and the Esquimalt Lagoon. It works out to about $85,000 a year. The CRD's goal is to prevent the amphibian's expansion into the Sooke Hills Wilderness Regional Park and the Greater Victoria Water Supply. But they have no money set aside to choke off the annual waves of frogs coming eastward from the peninsula.
With more money to buy more boats, make more electro-froggers, and hire more field staff, Orchard could deal with the Saanich bullfrogs conclusively. He calculates $30,000 would get him the equipment he needs to set up a new crew, and another $30,000 annually for wages and supplies.
“The dimwits from Ministry of Environment have been saying it would cost millions and millions of dollars [to eradicate the peninsula’s bullfrog population]. Well, we haven't spent millions and millions of dollars and we've been at it for years and years,” Orchard said with mild-mannered frustration.
“If I had a million dollars, I could have 22 crews arrayed through Greater Victoria, working right through the active season of American bullfrogs every year.”
As we paddled through that Metchosin pond, impressively loud croaks and ribbits called to us from around the perimeter. But they weren’t the sound we were hunting. American bullfrogs make a low sound that’s almost a growl. Like a grunt, similar to how crocodiles vocalize.
The audacious ribbit-ribbit that sounds clear across the pond—and is often used in pop culture for the sound of any frog—is a tree frog. Bullfrogs eat them for breakfast.