Why in the world would a cat lover want-or need-a cat repellent? Outdoor roaming cats use gardens as litter boxes, lounge on the hood of cars, chase birds away from feeders, spray to mark territory, and yowl loudly or even fight. Most important to you, though, indoor cats get their tails in a twist when a trespassing cat appears.

Indoor cats "own" all the property they can see through the window. Providing food for your own outdoor cat also draws strays to the food bar.

The mere presence of a strange cat within sight-and smell-can prompt hit-or-miss litterbox behavior, redirected aggression, and stress-related behaviors or health problems for your indoor pets.

Nobody wants to be cruel or unkind to unowned kitties. But your first obligation is to your own cats. Use these 10 tips to shoo away cats and keep them at bay.

10 Tips to Keep Cats Away

Find the owner. If you know the other cat is owned, contact the people involved. Be cordial, of course, and express concern that their cat is at risk for injury and disease-and also explain he's causing behavior problems with your own cats. Request the owners find a way to confine their cat either in safe outdoor environments or transition to indoors.

Manage ferals.Alley Cat Allies has great resources for helping feral cats. Should you decide to take on the responsibility, be sure the feeding station is some distance from your cats' window view to reduce their angst.

Rehome strays. Your local shelter should offer help with capturing strays and helping to find them homes.

If you fall in love with the needy stray, BRAVO! But be sure to introduce new cats properly to your resident cats.

Wash outside door or walls. Get rid of the urine spray or the cats will return to refresh the scent. Avoid bleach which smells attractive to cats and will increase spraying. Enzyme-based odor neutralizers are the best option.

Booby trap targets. For doors, try wrapping the bottom half in aluminum foil. The Ssscat shoos with a "hiss" of air when the motion detector is triggered and can be set nearly anywhere. You can also set up motion-detector water sprinklers like the Scarecrow. For the roofs and hoods of cars, place a plastic carpet runner nub-side up to make this warm place uncomfortable.

Clean up brush. Clutter provides habitat to prey animals that creates a mousy smörgåsbord that draws stray cats to your landscape.

Make digging difficult. Cats love soft soil to dig for pottying, so make it unattractive. Before you plant, line beds with chicken wire-vegetation grows through the wire but it's off-putting to the digging cat.

Mulch with stickers. Prickly cuttings from holly leaves, rose clippings, pine cones, or other uncomfortable material helps keep cat paws at bay. It's also environmentally friendly. Add the peels of citrus fruit (oranges, lemons, grapefruit) for an off-putting odor--cats don't like citrus smells.

Use commercial repellents. Many are available but they can have mixed reviews. If you don't have a cat, the ultrasound-repellent products may be an option but may bother your indoor cats and dogs. The Cat Stop product works with a motion detector and batteries, uses only a short blast of sound to shoo strays away, and has received positive reviews.

Landscape with cats in mind. Cats love mint, and also may be attracted to some types of honeysuckle, which prompts catnip-like reactions. Either remove these, or relocate the plants to areas that won't bother your own cats. Instead, plant vegetation like rue that smells bad to cats, in between your flowers.

You may not be able to permanently banish unwanted cats from your premises. But using these tips should go a long way toward keeping your cats happy and stranger cats at bay.