Causes of marking with urine
However, the issue of marking isn't so straightforward, because there isn't always a territory conflict behind this behaviour. We previously believed that cats simply marked the border of their territory with their urine, but behaviour researchers nowadays assume that cats also use marking as a means of communication with fellow felines.
Marking as a means of communication
Urine acts as a kind of visiting card for cats that reveals a lot about them. We humans can only guess what messages cats use to communicate amongst each other, but they probably show other cats who they are (male or female), where they were, whether they are healthy or stressed, ready to breed or wish to be left in peace.
Marking as a sign of readiness to breed
Compared to castrated males and neutered females, unneutered males mark most often of all. This would indicate that marking is often linked to reproduction. Males which to draw the attention of females in the neighbourhood to them and signal “hey, I'm ready!”. Hence, the urine contains information on sexual status and should trigger the female's willingness to mate.
Marking to define territory
However, males and females don't always wish to impress the opposite sex with their urine. Sometimes it's actually about territorial requirements. Urine allows them to signal to their competition: “This spot belongs to me! Paws off!”. Outdoors, for instance, these are promising hunting areas or shady spots to rest. At home they are feeding areas, the sofa or a cosy place to retreat. There are plenty of coveted resources in their territory, which aren't just marked by uncastrated mates, but females (neutered and unneutered) and castrated males too.
Marking due to stress
Nevertheless, cats sometimes also mark without having their territory or the opposite sex on their mind. This usually occurs due to uncertainty, stress and loss of composure. Even if cats themselves aren't aware of this, they unconsciously reduce stress by urinating. Marking with urine is therefore a kind of means to vent. This leapfrog behaviour is usually triggered by unsatisfied needs: a cat wants to go outside but the door remains closed. It is hungry but its food bowl remains empty. It wants to be alone and have space, but a loud party is taking place in its home. However, changes to their customs can also unsettle sensitive cats and lead to marking out of stress: moving to a new home, a renovation, a new sofa, a new carpet or the birth of a baby. Sometimes even little things suffice, such as using a new cat litter, an unusual smell (such as old sports clothing) or a new cat food variety.