Adapted by Paul Oester, Extension Forester, Oregon State University Extension Service from an article by, Joe Rojas-Burke, The Oregonian
As far as anyone knows, the U.S. had zero European gazelle beetles before 2007. That’s when a lone beetle turned up in samples collected in Corvallis by Oregon State University students. Now they’re staging a fullon invasion.
The exotic newcomers have spread across 10 Oregon counties and into Southwest Washington. At several sites, overwhelming numbers appear to be displacing native ground beetles. The gazelle beetles adapt to a variety of landscapes: from heavily disturbed industrial sites in Portland and Willamette Valley farm fields to wild mountain meadows and old-growth forests in the Coast Range. The half-inch beetle, known by scientists as Nebria brevicollis, earned its common name because of its speed.
“They feed on almost any invertebrate that they can overcome,” says James LaBonte, entomologist with Oregon’s Department of Agriculture who discovered the invasion. “What is not yet clear is whether it is or will become a damaging species.”
Most invasive species of ground beetles in North America appear to be harmless additions. The gazelle beetle’s rapid expansion, voracious appetite and extreme adaptability make it more worrisome. “It’s especially concerning that it is a predator that may have an impact on native species, including some that are endangered,” says Sarina Jepsen, endangered species program director for the Xerces Society, a conservation organization in Portland.
Little if any research exists on managing grounddwelling predatory beetles, says entomologist David Kavanaugh with the California Academy of Sciences. “I don’t know what we’d do if they turned out to be a problem,” he says.
In years of bug hunting, LaBonte first came across a European gazelle beetle in 2008, when he and Kavanaugh found more than a dozen one night on a casual collecting walk outside his house near Dallas. Later surveys by LaBonte and others that year found the beetles at 13 sites in five counties from Corvallis to Portland. LaBonte wasn’t particularly alarmed because exotic insects reach the Northwest every year and nearly all the gazelle beetles were on urbanized or developed farmland. Exotic species thrive in such disturbed habitat.
Then LaBonte found gazelle beetles proliferating beneath old-growth fir and hemlock trees near the top of Marys Peak west of Corvallis, the highest point in Oregon’s Coast Range at more than 4,000 feet. The peak is typically snow covered from mid November until April. The beetles had colonized the forest, meadows and rocky summit; often it was the most abundant beetle. On previous trips there, LaBonte found only native species.
“It was appalling to find this exotic species not only present, but very abundant in a habitat that’s normally pretty secure from exotic species,” he says.
Gazelle beetles may have arrived in Oregon in an overseas shipping container. Hitching rides on potted plants, sod, firewood, or yard debris trucked distances probably helped them colonize far and wide. Fully developed wings allow adult beetles to fly over rivers and other barriers.
Although the beetle doesn’t directly threaten agricultural crops or forests, it could trigger a damaging domino effect. Preying heavily on beneficial insects, or crowding them out, could leave crops more vulnerable to pests. Plants gain protection from a variety of native predators to check plant-eating insects. When a single exotic species dominates, it can’t match the range of prey and activity period of a broad mix of native species.
The invasive beetles could directly threaten endangered butterfly species in Oregon. The beetles have reached Mount Hebo, one of the few remaining habitats of the threatened Oregon silverspot butterfly. The beetle thrives in similar environments as does the endangered Fender’s blue butterfly in the Willamette Valley. No one has documented the beetles eating silverspot or Fender’s blue butterfly eggs, caterpillars or cocoons, but LaBonte says the beetles would have no trouble finding them. Gazelle beetles climb shrubs and grasses, unlike their more earthbound relatives. Catching the invasion fairly early gives researchers a window of opportunity to predict how harmful it could become. But only if funding agencies support the efforts.
“It isn’t everywhere yet,” LaBonte says. “That gives you the opportunity to examine the insect communities where it is not present, then compare those in a similar setting to where it is present. Once its all over the place, you won’t be able to do that.”