Portola Valley promotes safer rodent control


By Kate Daly

Special to the Almanac

Portola Valley is turning a common pest problem into a plug for environmental preservation.

Last March the Town Council voted to urge local businesses to stop selling rodent poisons, and encourage residents to use integrated pest management practices when dealing with rats, gophers, mice, voles and squirrels.

The town's Conservation Committee recently held an hour-long presentation at Portola Valley Community Hall to educate residents on moving to safe and sustainable rodent control.

"We can all agree rodent pests can cause damage and carry diseases ... but when we poison rodents we're poisoning the whole food chain," said committee member Nona Chiariello, who introduced six speakers to the audience of about 60.

The rodenticides on the market now contain ingredients such as brodifacoum, bromodiolone and difethialone, which act as anticoagulants and make animals bleed to death. The poison may take a while to kill rodents, so they might keep eating bait and increase the toxicity level, and/or wind up in a weakened state, making them easier prey.

Either way, studies show predators such as raptors, coyotes, bobcats and mountain lions are dying in increasing numbers after eating poison-laced rodents.

According to a WildCare brochure that was distributed at the event, each year, nearly 20,000 cases of rat poisoning in pets and children are reported to Poison Control Centers across the county.

"Portola Valley is one of 29 towns, cities and counties in California asking people to use something more humane, more effective, and safer," Ms. Chiariello said.

Town Manager Jeremy Dennis spoke about the pilot project taking place on the baseball field at Town Center, where mechanical traps have captured 25 or so gophers in the last three months.

He said to combat gopher, mole and vole damage, "We continue to use rodenticide on the other playing fields."

Portola Valley Ranch banned rodenticide use last November. The land manager there, Miriam Sachs Martin, shared ideas on how to keep pests out.

She suggested pruning vegetation away from houses, using wire gopher baskets around the base of plants, adding wire mesh baffles or skirts around tree trunks, and applying castor oil to the soil to repel gophers and moles.

As for rats, they are always on the lookout for shelter, food and water, so, she said, don't "free feed" them, meaning don't leave pet food out, or rotting fruit and bird seed scattered on the ground. Even an accumulation of dog poop will attract rats.

To prevent rats from getting inside, she suggested covering holes and gaps with copper mesh or inflatable caulking. A rat can fit through a space the size of a quarter; a mouse, a nickel.

"Live trapping is not an option," she said, going on to mention several "kill" traps to use "if necessary": Macabee steel rodent trap, Victor Rat Zapper and squirrel Tube Trap.

Paul Heiple, a Conservation Committee member from Ladera, talked about his own trapping experience. Moles "are insectivores, so you don't really want to go after them," he said.

He showed how he takes a Macabee trap and attaches a wire on one end to a stick so he has something to keep it anchored above ground, and then lowers two traps into a gopher's "main run," placing a trap going in each direction.

He did this in his yard and neighbors' field for about five years and is now gopher-free.

Brian Weber with the San Mateo County Mosquito and Vector Control District advised, "Use a tamper-proof box if trapping outdoors, otherwise you can catch other animals."

"Just trapping doesn't work; sanitation and exclusion works," he said.

The agency provides free rodent inspections to residents. A technician will come out, write an assessment report, and will work with pest-control companies.

Due to hantavirus and other diseases, Mr. Weber stressed the importance of extra caution by using gloves, hepa filters, disinfectant and double bags when cleaning up droppings and dead animals.

The final presenters, Jennifer Gale with CuriOdyssey and Jenny Papka with Native Bird Connections, showed off four live predators, or nature's version of rodent control: a peregrine falcon, barn owl, gopher snake and Western screech owl.

Ms. Papka jokingly called the barn owl "nature's mouse-o-matic," because a large family of owls can eat 3,000 to 5,000 rodents a year.

Some Portola Valley residents have already installed wooden barn owl boxes to try to lure the predators to their properties. A sample box was on display.

Locals recently had a chance to shop for a box at the Portola Valley Farmers' Market, where the Amador Barn Owl Box Co. had its model for sale.

Go to for information about that product.


1 person likes this
Posted by Birdnscrap
a resident of Portola Valley: Central Portola Valley
on Jan 15, 2018 at 5:16 pm

Use Protecta bait station boxes to contain your outdoor rat traps so you won't catch birds, pets, etc. Available throuh Amazon and other places.

Like this comment
Posted by Ginger Hummer Creevy
a resident of Portola Valley: other
on Jan 15, 2018 at 8:43 pm

Ginger Hummer Creevy is a registered user.

We have three barn owl houses and our close neighbors have another two for a total of 5 houses on 4.5 acres. - they were professionally installed and have never been inhabited.

I asked a raptor expert to visit and walk the property with me to determine our problem in attracting barn owls - as we had them nesting at our property back in the 90s before we had proper houses for them.
anyway, she cited that barn owls have left central PV for the most part because of Great Horned Owls which eat
Barn owl chicks.
So after 8 years we still have no barn owls and I suspect we never will. We use all possible methods for moles voles ground squirrels and rats. We have bee hives so do have lots of water available but try to eliminate food.
Good luck with the owl houses - I hope you get barn owls....

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