Author: Chris O’Neil, Founder, Catology – Cat Behaviour Solutions

Whenever I have a client come to me with a cat behaviour problem involving aggression, litterbox avoidance or spraying (about 85% of my consults), one of the investigative questions I ask is always, “Do you have an issue with neighbourhood cats”?

Most often the answer is no. But if I probe and ask whether they are sure, I often get another answer along the lines of, “well, there is one cat I’ve seen every now and again.  Jasper does get a bit funny when he comes around!”.

Now I’m not saying that neighbourhood/outside cats are THE reason for the behaviour problem (though often it is), but it is definitely most often a contributing factor.  I call it a “pressure point”.  Enough pressure points and you have an issue.

So let’s explore just why outside cats might cause problems for inside cats. 

The answer is to do with territory.

Territory is everything to a cat.  It is a place of comfort and security, as well as one to defend and protect.  It is so important that a lot of a cat’s day is spent patrolling and surveilling their territory.

There are a few different theories on how cats see their territory, but the generally accepted one is that (in their natural environment) cats have two parts to their territory – a home range and a home base.

Home Range

A home range is an area where a cat will hunt and explore. Most often, home ranges overlap with other cats’ home ranges.  Cats are generally happy to share a home range, and the size is often determined by the availability of resources.  The more resources (like food), the smaller the home range needs to be.  Some studies have shown that some cats can travel 10’s of kilometres each day exploring their home range!

Home Base

A home base, on the other hand, is a smaller, more concentrated area (within the home range), where cats eat, nest and sleep.  They may share this area with close associates, but is generally defended against other cats.  This is the warm heart of their territory.

When we keep cats indoors in our homes, the home base and the home range are generally one and the same.  Your home is now a castle to be defended.  

So, what happens when your indoor cat sees another cat outside?

Well, a whole range of things can manifest.

Some cats are (or seem – remember, we can’t ask them!) completely ok with it.  These are generally the confident cats who feel secure in their territory.

On the other end of the spectrum, a more anxious or territorial cat will see another cat as an immediate threat, resulting in redirected aggression, spraying, territorial urination, and even other stress-related behaviours like psychogenic alopecia (overgrooming to the extent that they create bald spots in their coat).

In the middle of the spectrum, you might find that there are no real outward signs of issues, until you bring another cat home, or make a change to their home environment (like someone else moving in to the house), when the cat will finally start acting out.  This is usually the point that my services are called in.  And often the owner’s focus is on the last change that happened, instead of the core, territorial issues that they aren’t seeing!

Given the quiet and often nocturnal nature of cats, sometimes owners have no idea of an outside cat problem. 

Here’s an all-too-common example.  Last year, a lovely couple from Melbourne called me out of sorts because their two 4 year-old siblings were fighting, with regular territorial spraying.

During the consult I asked where the location of the spraying was (a big clue).  They proceeded to show me – under every window at the front of the house, as well as next to the cat door at the side of the house.  These locations are a dead-giveaway of an outside cat problem.  The cats are “planting their flags” at the visual and entry points into the house. 

When I asked how often they saw outside cats, the couple replied that they hadn’t.  In fact, they swore that other cats never came around.  After a bit of back and forth, they agreed to set up a pet camera (you can get them fairly cheap these days) overnight and watch. Well, the next day I received an email to tell me that overnight seemed to be a hive of activity with neighbourhood cats! 

And they don’t even need to come right up to the window or near the house.  Cats don’t have a sense of fence boundaries like we do.  If the strange neighbourhood cat is simply in your cat’s view, even if it’s two backyards away, it’s a threat!

So how do we deal with neighbourhood cats that might be causing issues for yours?

It’s not always easy, but there are a few potential solutions.

First, try to work out if there is anything in your yard that is attracting the other cats.  Often it can be food left out (like dog food), or it could be a tree they like to climb, or even a bird bath that attracts their prey.  If you can remove the attractant, please do.

Most often though, your yard or area around your house will be part of another cat or cat’s home range and you’ll have to do more than just remove whatever is attracting the cat.

I’ve found that the most effective cat and other animal deterrent are motion activated sprinklers.  You can set them up so that when it detects the slightest movement, it can turn the sprinkler on and direct it at the cat.  These are great if your yard allows for it. It doesn’t take too long before the prowling cat decides your yard is a no-go zone.

If you have a fence around your property, you can also install Cat Netting to put on top of the fence to stop cats getting in.  These have the extra benefit of keeping your cats in, so you can let them out into the yard for some extra enrichment.

You’ll also need to patch up any entry points if that’s where the cats are getting in.

Lastly, perhaps if you know the cat’s owner, a quick chat may get her to keep her cat inside, though this may cause neighbourhood relationship issues so tread lightly here.  In saying that, the cat may actually be an inside cat and escaping without the owner’s knowledge.

If you can’t stop a cat getting into your yard, you may need to block the bottom half of some windows with a clouded window film that allows light in, but blocks the view.  This can stop your cat seeing the other cats and can help.

So as you can see, outside cats can cause big problems for inside cats.  Often times an owner may not even realise. So if you are dealing with any territorial or stress-related behaviours, like aggression, spraying or overgrooming, consider the possibility of outside cats, even if you don’t see them.  To be honest, if you live in suburbia, it’s a high likelihood that you have neighbourhood cats around!