DEAR JOAN: We have a nice big set of windows that faces a partial hillside backyard and flat grass area. We’ve had some pretty major gopher problems with mounds all over our yard that my son rakes down regularly.

We also have ground squirrels who live on the hill that we enjoy watching frolic around the yard. There were three babies and the parents, from what we saw.

In an effort to humanely get the mole problem under control, I sprayed a castor oil solution from Home Depot onto the yard. Reading up on this it said that it makes them go away because it gives them diarrhea and they will move to another area. I did note that I saw the ground squirrels also eating the grass as they were playing in the backyard.

We went on vacation for a week and a half and when we came back, I noted that the ground squirrels no longer made an appearance, although the gopher holes stopped. I did note some turkey vultures hanging out on the hillside, too.

My concern is that the castor oil did more than evacuate the moles. I think it may have sickened the ground squirrels and possibly killed them. I don’t have the heart yet to tell my family, and I feel really badly about the situation. Do you know more about how castor oil solutions work and if I should avoid using them in the future to not harm the ground squirrels?

Of course I was avoiding using any type of poison product based on your article stating that owls and other predators can be sickened by eating the rodents, and it was never my intention to kill the rodents, just evacuate them.

B. Lillie, Alamo

DEAR B.: You can stop feeling guilty. I don’t know what has stopped the activity in your yard, but castor oil is not a poison, and whatever you sprayed would have pretty much disappeared within a week.

It’s the castor beans, which actually are the seeds of the castor plant, that are lethal. It takes very little for a fatal dose. The seeds contain ricin, which is estimated to be 6,000 times more poisonous than cyanide and 12,000 times more poisonous than rattlesnake venom.

Castor oil is made from the seeds but the processing removes the ricin, making the oil safe to consume. It will give you diarrhea and can make you sick to your stomach, but it won’t kill you.

I believe the use of castor oil, either in homemade mixes or in purchased products, is not to give the animals a bad case of the runs and, presumably, stink up their lairs so much they have to move. It’s the odor of the oil that is said to deter the creatures. Apparently it does, although once the scent disappears, the animals return.

Castor oil is said to work, at least for a while, on both moles and gophers. Moles only eat insects, not plants, so they wouldn’t have eaten the treated grass. Gophers and ground squirrels might have consumed the castor oil, but the worst it would have done is give them tummy aches.

Hopefully, if your neighbors were suddenly treated to an influx of gophers and ground squirrels, they didn’t resort to poisons.

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