aggressive neighbor cat

Question
About two years ago, my neighbor adopted a hefty bobtailed male cat who promptly staked out the entire 4-unit apartment building and surrounding 30-foot radius as his turf.  Since the arrival of this new menace, my young male cat, a robust and healty five year-old, has been spooked, and now keeps a nervous lookout for this new rival, using the fence tops as a highway to evade him (the aggressor is afraid of heights.)  He clearly is not the same cheerful cat he was before.  In contrast, my other neighbor's tiny, elderly cat chased the newcomer out when he came through the open door of her apartment, which he also regards as his turf.  

He pries open the screen door at the bottom of the stairs and yowls in the hallway of the 2 upstairs units, then flees when I open the door to shoo him away.  He attacks the ankles of humans from ambush, then flees.  In short, he has the temperament of a bully.

Tonight was the last straw.  I heard his little footfalls outside my door to the upstairs hallway (while my cat stared at the door in alarm,) opened my door, and followed him downstairs to the front steps, where he hid next to the bushes.  He sat placidly there in the beam of my flashlight as I rebuked him, and then, as soon as I turned to go back upstairs, he lunged at me with a little cry and took a swipe at my ankle, which drew blood, and fled to safety.  He wasn't cornered and did not exhibit defensive body language, he did his usual "strike from cover and retreat" routine.

Can you explain why my neighbor's cat behaves this way?  Barring some extraordinary remedy, it appears to be time to start confining him indoors on a permanent basis.

Answer
Jeff,

Cats, like people, can be bullies. It doesn't sound like he is being mean when he attacks ankles, he is just playing. He is probabaly bored and lonely, and trying to get attention. And since he doesn't have a kitty friend to play kitty games with, he is playing with people like he would another cat (stalking, hunting, attacking his 'prey').

I would carry a rolled up newspaper and slap it hard against your leg, or whap him with it (it won't hurt him!) so the noise scares him. He will begin to associate the noise with trying to attack your ankles and hopefully back off from doing it.

His owner needs to spend more time with the cat and play with it to burn up some of the cat's energy. A pet laser light used inside or outside is a good way. You can get them at PetSmart, Petco, etc. Using one outside in and around the bushes can be hysterical to watch when the cat tries to get the "little red bug" at night.

If you get along with the cat's owner, maybe you can work out a schedule where the cat is kept in at certain times so your cat can go outside peaceably and safely.

Tabbi