How does a fox communicate with other foxes?
Mainly auditory; foxes have a very wide vocal range spanning 5 octaves.

contact calls
The most commonly heard contact call is a 3–5 syllable barking “wow wow wow” sound
interaction calls
When greeting one another, red foxes emit high pitched whines, particularly submissive animals. A submissive fox approached by a dominant animal will emit a ululating siren-like shriek

Foxes also communicate using non-auditory communication, such as different facial expressions and their bushy tail.

How does a fox communicate with other species?
It doesn’t.