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A frog for the killing

Amphibians may be declining worldwide, but Canada's largest species has had some human help in multiplying out of control.

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Like 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 fill 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 Dr. Purnima Govindarajulu, a herpetofauna specialist from the British Columbia Ministry of the 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 is 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 — literally and figuratively — a monstrous problem in hundreds of jurisdictions throughout Asia, Europe, Central and South America, the Western U.S. and now, British Columbia.

Here, releases and escapees loosed decades ago — whether by failed farmers (deluded schemers who dreamed of a fortune in frog's legs) or misguided gardeners who coveted the animals for ornamental purposes — seeded enough wetlands on lower Vancouver Island and in the Fraser River Valley east of Vancouver for the prodigious frogs to do the rest: multiply out of control to wreak havoc on local ecosystems.

The bullfrog's considerable impact begins with its preferred food, other frogs — particularly young ones — though it happily consumes crayfish, salamanders, snails, snakes, turtles, birds and even small mammals. It's also prolific: a single large female can deposit 20,000 eggs, a high proportion of which might survive, in part because most animals find bullfrog eggs and tadpoles distasteful.

After establishing itself in a water-body, the biggest threat the bullfrog poses is the elimination of native frog species through both predation and competition; by the time the invaders gleefully begin to feed on each other (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 bullfrog has already colonized adjacent wetlands, a hop ahead of any would-be control — 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 most areas there's no hope of eradication — it's either too expensive or would require control forever," she says, conscious of the speculative $3.7 – $37 million per year, based on case studies, that it would cost to do so on Vancouver Island (the estimate for control in Rhineland-Pfalz, an area of comparable geographic size in Germany, is $350 million CAD). "So it's better to put money and effort into habitat restoration for native species and hope for some balance of co-existence. Then stop bullfrogs from spreading by increasing public education."

In Victoria and environs, where the time, energy and planning focused on bullfrogs by commercial, academic and community groups is already incomprehensible, the ministry of the environment promotes control through websites, bookmarks, brochures and talks, providing hands-on training to both professional and amateur conservationists in identification, water safety, animal care and culling methodologies. Which brings us back to Trevlac, whose invasion also offers lessons in bullfrog reproductive ecology.

From every quarter bullfrogs sound off, the depth and resonance of their calls indicative of size. "Boomers" — the largest males — space themselves out at prime calling sites. Between them lurk smaller "satellite males" that seek to intercept the females boomers lure, and more insidious "sneaker males," which will 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 in order to facilitate external fertilization; once in amplexus, frogs are too hormone-addled to fight off any challenges.

Their glowing eyes frozen in our lamps, frogs the size of puppies are soon accumulating in the anesthetic 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 in 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 engineer who runs a furniture company and got sick of bullfrog soup," he says, referencing the lake he lives beside. In fact, despite her feigned enthusiasm, neither Whitehouse nor Grigg, or 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," Grigg croaks. "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.

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 motionless hand through a spray of reeds and then, like lightening, makes the grab. The frog, as long as her forearm, makes us wonder 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 in anesthetic. The skin samples, which will later be scanned under a microscope, 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: it's a natural vector of chytrid (Batrachochytrium dendrobatidis), the highly contagious, freakishly pathogenic fungus fingered in a worldwide decline of amphibians that has seen dozens of species disappear forever and hundreds more pushed to the edge of extinction. Swabbing in British Columbia has revealed that chytrid is always present in ponds that contain bullfrogs, while in ponds without bullfrogs the fungus may or may not be detected.

On shore we check the catch — 35 breeding adults between us — 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 frogs. 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 preserve their environment," says Govindarajulu. "And they've tried to make it fun to keep the enthusiasm up because they understand that bullfrog control is a long-term effort."

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, the number of invasive plants and animals affecting the Canadian economy through lost revenue and control or eradication costs increases. Familiar examples include Dutch elm disease, Japanese knotweed, purple loosestrife, common carp, zebra mussel, gypsy moth and emerald ash borer. Control of the sea lamprey, for instance, an eel-like parasite of game fish that destroyed Great Lakes fisheries during the 1940s and 1950s, amounts to $20 million a year, while controlling other invasive organisms in those same waters, as well as the forestry and agriculture sectors, ring 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 lithosphere.

Next day we wind further inland, parking in front of an immaculately landscaped mansion in an ostentatious subdivision. Engelstoft wants to show us something, and walks us over to a rock wall topped by a cedar hedge. They take a few minutes to spot in the shimmering heat, but scuttling under cedars and lodged in cool crevices we find dozens of emerald-backed Italian wall lizards, Podacris muralis. 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 Farm, in Saanich, where the highly active predators swarm greenhouses with uncertain consequence to both pollinators and pests. Given the apocryphal tales of other Podacris habitats being virtually devoid of insects, there's more than one thesis in the making to understand its impact. Though Engelstoft has investigated several theories, no one really knows how an Italian lizard immigrated to British Columbia. 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 some 80 sites spread along a vast stretch of the Fraser River, where regular floods help 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," Murray said. "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," Murray said. Though large, an adult green is still only a third the size of a big boomer; so far, they weren't eating absolutely everything and appeared to co-habitate with Oregon spotted frogs. But this much was clear: eradicating either invader would be impossible in this floodplain of annually connecting and disconnecting wetlands, and you'd have to take out the greens, which were far too numerous, in order to get to the bulls.

"Only in places like the Okanagan where populations are so far contained, do you have a good chance of eradication worth putting money into," Govindarajulu told me at Trevlac, of an emerging small triumph. In collaboration with the University of Waterloo, Environment Canada, private landowners, the Land Conservancy of British Columbia and South Okanagan-Similkameen Stewardship programs, the ministry of the 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 you can declare an eradication 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, Saltspring and Lasquiti 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 this 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 it funded by the Capital Region Commission responsible for the watershed. Whatever the politics, that's significant biomass — a huge dent in the population that could have been.

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 on another sultry evening, 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 Zodiac 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 Zodiac. Positive and negative terminals are both on a long-handled wand that also features a small, boomer-sized net. Orchard calls it a Frogshocker and has a patent on it, selling the equipment to wildlife agencies in the U.S. that 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 removes thousands in the same period — 3,000 this year 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 a decade of effort, the pests continue to spread further afield, presenting an ever-distant frontline.

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 a half-dozen garter snakes complete their morning rounds underfoot, Govindarajulu, in chestwaders, checks traps left out for tadpoles. It's not a great haul — only two — but they're big ones that will metamorphose this summer. One is a red-legged frog with rear limbs. Red-legged frogs, listed as threatened in British Columbia, breed in February, which would seem to confer ecological advantage over the invaders, which breed in July. But bullfrog tadpoles stay in the water two years, and constitute competition over the entire course of a red-legged tadpole's life. If this one metamorphoses, it will then have to survive a ravenous gauntlet of sub-adult 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 seem especially skittish. "Bullfrogs learn fast," insists Kimura. "If you miss one on the first attempt each subsequent one is harder."

Packing up, the crew demonstrates its dedication to the cause. It takes 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 them 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 that a lake has been drained in Burnaby, B.C., in order to find a highly invasive Asian northern snakehead fish, followed by another item about a tourist in the B.C. Interior found carrying highly invasive quagga mussels on his boat 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 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.

Dealing with bullfrogs and other 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. For marauding bullfrogs in the Victoria area there are a wealth of resources that outline preventative measures, what you need to know to deal with them (bullfrog identification, for instance, is key to not harming threatened indigenous species — or bullfrogs in their home range). Resources and links for your own area and/or other plants and animals are easy enough to find on the Internet, but here are some starting points:

Federal: invasivespecies.gc.ca for a national overview.

Provincial: ec.gc.ca/eee-ias/default.asp?lang=En&n=B46F7A36-1 (list of provincial resources); invadingspecies.com (Ontario).

British Columbia: bcinvasives.ca lists the threats and links to phone apps like "Report-a-weed."

B.C. Frogwatch: env.gov.bc.ca/wld/frogwatch/publications/factsheets/frogs/bullfrog.htm is the starting point for amphibian I.D. and conservation threats like the bullfrog.

Sea-to-Sky Invasive Species Council: ssisc.info keeps an eye on the corridor, does hands on-work in invasive plant eradication, and bullfrogs are on the list of potential threats to the area (Squamish, Pemberton more than Whistler).

Leslie Anthony is the Whistler-based author of Snakebit: Confessions of a Herpetologist. His science, travel and adventure writing appears in explore, Canadian Wildlife, Canadian Geographic, and magazines around the globe. His next book, The Aliens Among Us: How Invasive Species are Taking Over the Planet, will be published by Yale Press in 2015.

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