Leaving a Mark

Cats communicate face to face through voice and body language.

They also leave signs on their territories that can be read in their absence. Boundaries are marked with urine, feces, and scented chemicals, rubbed against upright objects.

These are not warnings, but simply mark the territory as occupied. When a cat rubs against its owner’s leg, we interpret it as affection. In part it is, but it is also a territorial marking.
 
Visual markers, such as scratches on trees, are also important. This visual aspect of cat's language means that urban cats often use the same markers that we recognize-such as hedges or walls - as their boundaries.