With photography by

Bullfrogs are threatening the ecological balance of British Columbia’s wetlands. (Photo: Deddeda )

A map of the regions affected by bullfrogs. (Map: Chris Brackley/Canadian Geographic)

Like the coin in a giant slot machine, a blood-red sun inserts itself into a cleft between two hills overlooking the Highlands rural residential area outside Victoria, B.C. At Trevlac Pond, where a jigsaw of cars and canoes fills a small driveway beside a woodland cottage, the mid-July gloaming buzzes with more than mosquitoes as teams and equipment are sorted. One boat will carry Purnima Govindarajulu, a reptile and amphibian specialist with the B.C. Ministry of Environment, biologist Christian Engelstoft and Hitomi Kimura, a biological technician at Vancouver Island University in Nanaimo; a second will contain Neville Grigg and Pattie Whitehouse of the Highlands Stewardship Foundation, a volunteer citizen group that promotes the health of local lakes; and a third will bear the interlopers — myself and photographer Deddeda.

We shuttle canoes to the heavily vegetated shoreline while Grigg, last to arrive, uncrates his gear: headlamps like the rest of us, a white restaurant bucket like Govindarajulu’s crew and, uniquely but more ominously, a copper-tube spear topped with what appears to be a giant fish jig — four devilish prongs, each of which sports a menacing barb.

Upturned spear in hand, Grigg stands next to Whitehouse, their headlamps on. In this rural setting, complete with cabin behind them, the scene conjures the Grant Wood painting American Gothic. But this is no dour couple: the pair are considerably animated and certainly more bloodthirsty. When a sonorous chorus breaks out around the pond — the beaver-flooded former peat mine that’s now an inky blot beneath looming forest — Whitehouse’s grin widens. “Let’s go massacre some bullfrogs!”


If you grew up in eastern North America where it is native, there’s something decidedly romantic about the bullfrog. Its throaty jug-o’-rum is the bass track of steamy summer nights from Ontario to Florida, its size and ubiquity further enshrined through children’s stories — the wise, sedate one perched on a log, overseeing a swampy kingdom of dragonflies and lily pads. The mind’s eye variously sees a lover of water and of land, a prince and a pariah, a symbol of good luck and of bad, a familiar but friendly enigma.

If you live in a growing list of elsewheres, however, the American bullfrog (Lithobates catesbeianus) presents a different reality. Widely recognized as one of the world’s 100 most invasive species, it has become a monstrous problem in hundreds of jurisdictions throughout Asia, Europe, Central and South America, the western United States and now British Columbia.

Here, bullfrogs that were released by failed farmers (deluded schemers who dreamt of a fortune in frog legs) or escaped from misguided gardeners (who coveted the animals for ornamental purposes) decades ago seeded enough wetlands on lower Vancouver Island and in the Fraser Valley east of Vancouver for their spawn to do the rest: multiply out of control and wreak havoc on local ecosystems. (Bullfrogs are prolific: a single large female can deposit 20,000 eggs at a time, a high proportion of which might survive, in part because most animals find bullfrog eggs and tadpoles unpalatable.)

The biggest threat bullfrogs pose after establishing themselves in a water body is the elimination of native frog species through both predation and competition. Their considerable impact begins with their preferred food, other frogs — particularly young ones — though they happily consume crayfish, salamanders, snails, snakes, turtles, birds and even small mammals. By the time the invaders begin to feed on one another (because there’s little else left and smaller bullfrogs are a perfectly acceptable food), it’s usually too late for the species they’ve displaced to recover and the opportunistic and fast-dispersing bullfrogs have already colonized adjacent wetlands, a hop ahead of any would-be control, including pursuers like a Victoria-area business that guarantees bullfrog eradication.

Not everyone, however, is convinced of the efficacy of such initiatives. Govindarajulu, for instance, who studied Vancouver Island’s bullfrog invasion for her Ph.D., believes the problem here is too far gone to be fixed. “In many areas, there’s no hope of eradication — either it’s too expensive, or it would require control forever,” she says, conscious of the speculative $3.7 million to $37 million per year, based on case studies, that it would cost to do so on Vancouver Island (the estimate for control in Rheinland-Pfalz, a state in southwest Germany that is of comparable geographic size, is Cdn$350 million). “So it’s better to put money and effort into habitat restoration for native species and hope for some balance of coexistence, then stop bullfrogs from spreading by increasing public education.”

Produced for the Wilderness Committee, this short documentary tells the story of the Oregon Spotted frog population in the Fraser Valley, which is declining in part due to the American Bullfrog. (Credit: Mike McKinlay/Wilderness Committee)

In Victoria and environs, where the time, energy and planning that commercial, academic and community groups focus on bullfrogs are already incomprehensible, the B.C. Ministry of Environment promotes managment through websites, bookmarks, brochures and talks, providing handson training to both professional and amateur conservationists in identification, water safety, animal care and culling methodologies. Which brings us back to Trevlac Pond, whose invasion also offers lessons in bullfrog reproductive ecology From every quarter, bullfrogs sound off, the depth and resonance of their calls indicative of their size. “Boomers” — the largest males — space themselves out at prime calling sites. Between them lurk smaller “satellite males,” seeking to intercept the females boomers lure, and more insidious “sneaker males,” which surreptitiously release their own sperm over eggs being extruded by a female in flagrante delicto with another male — i.e., amplexus, the two-armed death grip male amphibians employ to facilitate external fertilization; once egg-laying starts, frogs are too hormoneaddled to fight off any challenges.

Their glowing eyes frozen in our lamps, frogs the size of puppies are soon accumulating in the anaesthetic solution sloshing in the buckets (sedated frogs are later frozen and then either composted or distributed to university research projects in neuroscience, parasitology and genetics). The hunting canoes split up to cover more ground, and we follow the Highlanders. When they spot a frog, Whitehouse manoeuvres in while Grigg remains poised in the bow with the jig until he’s ready to plunge it through the animal, which is impaled and unceremoniously dumped into the bucket. When I note he’s quite good at this, Grigg shrugs. “Sadly, it’s a job that needs to be done. I’m just an entrepreneur who runs a furniture company and got sick of bullfrog soup,” he says, referencing the lake he lives beside. In fact, neither Whitehouse, despite her feigned enthusiasm, nor Grigg nor anyone else, for that matter, enjoys killing these creatures. After all, it’s not the frogs’ fault that they’re invasive, destructive pests outside their natural habitat — it’s ours.

The tuba voice of a huge boomer erupts near a large floating island. “That’s gotta be the granddaddy of all time,” croaks Grigg. “He’s mine!” But the Barry White of bullfrogs eludes detection.

When we catch up to the biologists, we discover that Govindarajulu, too, is in hot pursuit of Mr. Big. “He’s so sexy,” she says, peering through the tangle of shoreline wood she’d have to brave to reach him. “I’d happily get all scratched up for that guy.” Clearly, identifying with your prey is a way of distancing yourself from the realities of extermination.

Researcher Hitomi Kimura swabs a bullfrog from Trevlac Pond, near Victoria British Columbia. The skin cells will be analyzed for the presence of a fungus that has been blamed for amphibians’ worldwide decline. (Photo: Deddeda)

The biologists can’t find Mr. Big either and soon bear down on another quarry squatting on a muddy bank. Govindarajulu doesn’t use a spear, preferring the more humane method of hand-capture, which requires a good deal of experience and the canoe to be much closer. She snakes her hand through a spray of reeds and then, like lightning, makes the grab. The frog, as long as her forearm, leaves us wondering about the size of the one we can’t find. She admires it for a second before passing it to Kimura, who fastidiously swabs a few skin cells from the creature before dropping it into the bucket. The skin samples, which will later be sent to a lab for examination, relate to another can of worms opened by the presence of non-native amphibians.

A proclivity for mass consumption of fellow amphibians is certainly bad news given the number of endangered native forms where bullfrogs have been introduced, but a related issue could also prove deadly. Bullfrogs are a natural vector of Batrachochytrium dendrobatidis, the highly contagious, freakishly pathogenic chytrid fungus fingered in a worldwide decline of amphibians that has seen more than 100 species disappear forever and hundreds more pushed to the edge of extinction. Swabbing in British Columbia has revealed that the fungus is always present in bullfrog-infested ponds, while in ponds with no bullfrogs, the fungus may or may not be detected.

On shore, we check our catch — 35 breeding adults — and swap stories. Grigg recalls his record 65-frog haul and speaks of the need to control not only your own wetland but those around you as well, particularly smaller places like Trevlac, whose bullfrog population, if left intact, will continue to seed nearby lakes supposedly cleared of bullfrogs. Whitehouse mentions the upcoming Merville Frogfest, an annual August affair that takes bullfrog control to new — and delicious — levels. Cooked frog legs and other novelties are a hallmark.

“Merville’s program is a grassroots effort — non-biologists taking on invasive species to control their environment,” says Govindarajulu. “And they’ve tried to make it fun to keep the enthusiasm up because they understand that it is a long-term endeavour.”

There’s a moment of silence and then, mocking us, a loud, low thrumming from the middle of the lake. Mr. Big is still out there.

With massive, herbivorous tadpoles that graze ponds like cattle and highly carnivorous, often cannibalistic adults, the bullfrog is, in the words of one researcher, “the food web personified.” It is, however, just one extra-large, extra-obvious organism in a litany of Vancouver Island invaders that is itself a microcosm of a much greater problem.

Each year sees an increase in the number of invasive plants and animals affecting the Canadian economy through lost revenue and control or eradication costs. Familiar examples include Dutch elm disease, Japanese knotweed, purple loosestrife, the common carp, the zebra mussel, the gypsy moth and the emerald ash borer. Control of the sea lamprey, for instance, an eel-like parasite of game fish that invaded the Great Lakes via the St. Lawrence Seaway in the 1950s, amounts to $20 million a year, while controlling other invasive organisms in those same waters, as well as in the forestry and agriculture sectors, rings up annual price tags in the tens of billions. Aliens that can alter entire landscapes (Scotch broom), pose toxic hazards (giant hogweed) or carry disease (West Nile virus) are now a reality of globalization. Like it or not, along with climate change, ocean acidification and the sixth great extinction, invasive species define the Anthropocene, the current epoch of a human-altered ecosphere.

Next day, we wind farther inland, parking in front of an immaculately landscaped mansion in an ostentatious subdivision. Engelstoft wants to show us something and walks over to a rock wall topped by a cedar hedge. Although it takes us a few minutes to spot them in the shimmering heat, we find dozens of emerald-backed Italian wall lizards (Podarcis muralis) scuttling under cedars and lodged in cool crevices. They’re all over this neighbourhood and the next, in an ever-widening circle of dozens of square kilometres, with satellite populations in places like sprawling Haliburton Community Organic Farm, in Saanich, where the highly active predators swarm greenhouses, with uncertain consequences to both pollinators and pests. Given the tales of other Podarcis habitats being virtually devoid of insects, there’s more than one thesis in the making to understand the lizard’s impact. Although Engelstoft has investigated several theories, no one really knows how an Italian lizard immigrated to British Columbia. Its origins, however, are ultimately moot. Like the bullfrog, it is simply here and spreading fast.

Geographic spread doesn’t always equate with ubiquity, however, as regional factors come into play. Earlier in the summer, I’d spent an evening in Abbotsford with Rylee Murray, a field researcher working in concert with Govindarajulu and Simon Fraser University in Burnaby, conducting occupancy modelling for bullfrogs on 71 sites spread along a vast stretch of the Fraser River, where regular floods may be helping move the pests around. Of added concern here was the bullfrog’s potential impact on British Columbia’s four remaining populations of Oregon spotted frog, a species on the cusp of extinction.

Parking on a quiet street adjacent to a park, we walked 50 metres in the dark to the edge of a small lake. Lily pads reflected in the moonlight, and geese honked obnoxiously on the far shore, but we could hear the deep thrum of a boomer to our left and another to our right. Bullfrogs were here too, deep in suburbia. “We don’t often get big choruses though,” said Murray. “There’s usually only one or a few calling.”

Sure enough, at our next stop, a chugging chorus of green frogs — another invasive eastern species that has become extraordinarily abundant — drowned out a handful of bullfrogs. “It makes you wonder why we’re not more concerned about green frogs,” said Murray. Although large, an adult green is still only a third the size of a big boomer; so far, the green frogs aren’t eating absolutely everything and appear to cohabit with Oregon spotted frogs. But this much is clear: eradicating either invader would be impossible in this flood plain of annually connecting and disconnecting wetlands, and to get the bulls, you’d have to take out the greens, which are far too numerous.

“Only in places like the Okanagan, where populations are so far contained, is there a good chance of eradication worth putting money into,” Govindarajulu says of the emerging small triumph in the region. In collaboration with the University of Waterloo, Environment Canada, private landowners, The Land Conservancy of British Columbia and the South Okanagan-Similkameen Stewardship Program, the B.C. Ministry of Environment appears to have squelched an invasion near Osoyoos. But the effort has been costly — approximately $250,000 over a decade.

Natasha Lukey, a master’s student in environmental studies at the University of Waterloo, has also quantified the overall human effort of countless volunteers and field assistants since bullfrogs were first detected in the South Okanagan in 2003. Nighttime canoe searches for adults required five hours per bullfrog; active day searches for egg masses and tadpoles cost 85 hours per bullfrog; live trapping took eight days per tadpole, juvenile or adult. In addition, auditory surveys for calling males required 552 man-hours per detection. “We’ve installed permanent auditory recording devices at high-risk locations,” says Lukey of the hope to make monitoring more efficient. “We have 3,140 hours of automated recordings.”

According to Govindarajulu, five years of no frog sightings (or sounds) are required before an eradication can be declared successful. That’s a lot of listening.

Wherever there are significant numbers of people on Vancouver Island, there are significant numbers of bullfrogs. Victoria, Nanaimo, Duncan, Port Alberni — even offshore idylls like Pender, Salt Spring and Lasqueti islands. Which is why biologist-entrepreneur Stan Orchard can run a business based on bullfrog extermination. At odds with Govindarajulu’s position of organized control and facultative eradication, Orchard believes bullfrog extermination can be accomplished anywhere with enough manpower and effort (read: enough money). Feasibility notwithstanding, it’s hard to argue with results: as of 2012, Orchard’s BullfrogControl.com Inc. had removed 30,000 bullfrogs from Victoria-area waterways since 2007, much of the work funded by the Capital Regional District responsible for the watershed. Whatever the politics, that’s significant biomass and a huge dent in the bullfrog population.

The first time Orchard was called to the Cordova Bay Golf Course, 15 minutes north of Victoria, where we meet him and assistant Kevin Jancowski, it was because of a municipal noise violation. Owners of expensive condos overlooking one of the course’s several ponds had repeatedly complained of “foghorns” outside; some reputedly even put their units up for sale. “We took out 14 big males on our first visit,” says Orchard as he inflates a small boat and loads in powerful, homemade lamps that run off motorcycle batteries. To stun frogs, Orchard employs a self-modified electrofisher instead of the backpack version fisheries scientists use; the power unit sits upright in the boat. Both positive and negative terminals are on a long-handled wand that features a small boomer-sized net. Orchard calls it the electro- frogger and has a patent on it, selling the equipment to U.S. wildlife agencies that have failed in their own efforts with high-powered rifles. The French had also used rifles in a not-so-successful campaign that landed them only 120 frogs over 10 months. Orchard removed thousands in the same period — 3,000 in 2012 and 5,500 in 2011. According to Orchard, the declining totals could be misleading; yes, bullfrogs appear to have been vanquished from some areas around the city and prevented from entering others, but despite nearly a decade of effort, the pests continue to spread farther afield, presenting an ever distant front line.

Battles have clearly been won, but without legions of Orchards and millions of dollars, the war, as Govindarajulu holds, is lost.

We return to Trevlac the next morning to check in on the bullfrog’s other life stages. While half a dozen garter snakes complete their morning rounds underfoot, Govindarajulu, in chest waders, checks traps left out for tadpoles. It’s not a great haul — only two — but they’re big ones that will metamorphose this season. One is a red-legged frog with rear limbs. Listed as threatened in British Columbia, the red-legged frog breeds in February, which would seem to confer ecological advantage over the invaders, which breed in July. But bullfrog tadpoles stay in the water for two years and constitute competition over the entire course of a redlegged tadpole’s life. If this one survives to metamorphose, it will then face a ravenous gauntlet of subadult bullfrogs patrolling the pond’s edges.

Checking for egg masses, we circle the pond in canoes. Kimura and Govindarajulu tiptoe on floating islands, scouring the edges. But we find nothing. Our night assault seems to have impacted breeding here, and the remaining frogs are especially skittish. “Bullfrogs learn fast,” says Kimura. “If you miss one on the first attempt, each subsequent one is harder.”

Packing up, the crew demonstrates its dedication to the cause, spending 30 minutes to carefully spray the gear with a weak solution of bleach. Such fastidious cleaning obviates the transport of seeds, viruses, bacteria and fungi like chytrid to other water bodies. It’s a lot of effort but frees the crew from worry over spreading disease or perpetuating further invasions. Nevertheless, there’s no escaping the problem that’s in everyone’s face this summer.

Snapping on the car radio, we hear a report about a lake being drained in Burnaby to find a highly invasive Asian northern snakehead fish, followed by another news item about a tourist’s boat in the B.C. Interior found to be carrying highly invasive quagga mussels on its hull. And then there’s Govindarajulu’s own reality: while we were out frogging, two voracious eastern snapping turtles, which don’t occur naturally west of the Mississippi River Basin, have been found on Vancouver Island, and she and Engelstoft are off to investigate the nearby site where one of them was discovered laying eggs ... in a roadside nest.

Read about Kevin Jancowski and Stan Orchard’s recently published research on the stomach contents of American bullfrogs.

Resources for dealing with invasive species

Governments are notoriously shortsighted when it comes to invasive species, concentrating limited resources only on demonstrated economic or health threats. Thus, despite most levels of government in Canada having invasive species committees of some kind, the approach is decidedly piecemeal and municipalities too often find themselves on invasion frontlines that they’re unequipped to handle — the reason volunteer citizens groups predominate on the ground. Responsibility for invasions begins with individual awareness of the costs of accidental introductions. Specific resources for your own area are easy enough to find online, but here are a few starting points.


British Columbia





gouv.qc.ca (pdf)

New Brunswick

Nova Scotia

Prince Edward Island

Newfoundland and Labrador


Northwest Territories

gov.nu.ca (pdf)