Hundreds of ground squirrels have invaded Finch Arboretum and are turning the grounds into Swiss cheese.
Even worse, it’s breeding season.
Spokane Parks officials are mounting a counterattack with a commercially available weapon – the Rodenator Pro — that injects their burrows with propane and oxygen and sparks an explosion that shakes the ground and collapses their furrows.
It also turns the little critters into fertilizer.
“Something needed to be done,” said parks worker Doug McKay after detonating one hole on Monday.
Normally, ground squirrel populations would be kept in check by natural predators such as hawks, snakes and coyotes. But urban development has altered the natural ecosystem, allowing the rodents to thrive.
They’ve been a problem at the arboretum for years, but the population really started exploding about two years ago, said gardener Sally Sullivan.
“They are all over the place,” said Steve Nittolo, the city’s horticulture supervisor.
He and Sullivan estimated that the arboretum has 200 to 300 of the squirrels, which can be seen scurrying across the grounds or bobbing their heads out of their holes to keep an eye out for trouble.
The squirrels love the cultivated spaces where newer trees are growing, and their burrows damage tree roots in the arboretum’s large collection of species. In addition, the holes drain away sprinkler water, preventing it from soaking into the ground evenly.
Last year, one elderly man tripped in a hole near the parking lot and both he and his wife tumbled to the ground, Sullivan said.
Nittolo said he received one complaint a year ago from a neighbor concerned about the spread of disease from the squirrel infestation.
Parks officials are warning residents to be careful when they walk through the arboretum because of the holes.
According to the company’s Web site, the Rodenator causes “an instantaneous underground shock wave of concussive force that eliminates the pests and in some (species specific) cases collapses some of the existing tunnel structure thus preventing immediate reinfestation.”
Because it uses propane and oxygen, the Rodenator causes no environmental problems, unlike poisonous chemicals. Also, it leaves the rodents in the ground to decompose.
The Rodenator attacks have been stepped up in recent days in an effort to reduce the population before breeding increases their numbers.
Police have recently responded to the arboretum after receiving reports from neighbors who heard the explosions, and parks officials want residents to know that the noise is coming from the Rodenator.
“The hope is to manage the population prior to their reproductive cycle,” according to a park press release on Monday.