What’s digging all those holes in Walnut Creek open space?

DEAR JOAN: My husband and I are lucky enough to live near the Sugarloaf open space, where we hike most mornings.

This year, we have noticed the proliferation of large holes that look like burrows in the open space. We are wondering, what animal is making them? Because so many of them are near trees, do they hurt the root systems?

Barbara Lillich, Walnut Creek

DEAR BARBARA: Those multiple, open holes in the landscape are the handiwork of California ground squirrels, interesting little critters than can sometimes cause big trouble.

Ground squirrels like to colonize in large, grassy areas, which means they can inhabit any irrigated plot of land. They dig sometimes extensive tunnels, creating chambers for sleeping, storing food and hiding from danger.

The entrances into the tunnels are open on the surface, but entrances to important chambers below can be sealed with dirt to protect what’s inside. Although they raid gardens, gnaw on plants and even girdle trees by chewing rings of bark off them, some of the damage is unintentional and just the consequence of excavating tunnels.

Burrows and tunnels can remove the earth around roots, causing the roots to dry out or preventing the plant from taking up moisture and nutrients. Buildings, foundations and sidewalks also can be damaged when the digging beneath them is excessive.

Controlling ground squirrels can be difficult as they are hard to reach inside their tunnels. In open spaces, it’s often best left for nature to deal with nature. Ground squirrels are the favorite food of raptors, coyotes, foxes and badgers. Coyotes and badgers often hunt ground squirrels together. They attack, and if the ground squirrel goes on the run, the coyote chases them down; if they head into their tunnels, the badger digs them out.

DEAR JOAN: Can I give my cat milk or cream regularly?

Denise, Antioch

DEAR DENISE: It’s probably not a good idea. Most cats are lactose intolerant. Once weaned, they just can’t easily digest milk or cream from another animal.

If your cat can tolerate it, then it’s best to give the cat very little — and not very often.

Cats vs. Christmas trees

After answering a question from a reader whose cat tried to destroy Christmas last year by attacking the tree, I heard from readers who have successfully served in the Christmas tree wars.

DEAR JOAN: The crucial thing regarding Christmas trees and cats is that the cat never sees you bring in the tree and never sees you decorate it. Both of these actions translate to “play.” If my  cat doesn’t see me “playing” with the tree, he ignores it. All bets are off with young kittens, however!

Kathe, Berkeley

DEAR JOAN: Many years ago, my husband installed a very sturdy hook in the ceiling above where we always put the Christmas tree. We tie the tree to the hook, making it impossible for our three cats to knock the tree over.

We also put plastic and felt ornaments on the bottom of the tree, and put the glass ones at the top. We don’t mind if the cats knock one of the plastic or felt ones off, but we want to protect those glass ones.

Alexa S., Oakland

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