CRANKY KITTY

Hello out there dear A2K buddies. It has been AGES since
I've been here. I almost forgot the name of this site & you
know THAT is serious. I have a male cat, less than a year
old. He was scheduled to be spayed/neutered (whatever)
but one week prior he went a-travelin' & was hit by a car,
crushed his back left knee along with severe vascular
complications, so he lost the entire leg.
It's been over 4 months since his amputation & neuter
surgery so I would think he'd behave far less aggressively
(where's all this testosterone-like behavior coming from???)
He's taken to being mean, rude & hateful to Chloe. She is
3 years older than him & she was here first after all. His
tail has become pretty much entirely rigid since surgery
but it doesn't seem to cause him any pain or grief - and I'm
sure it helps him with balance, he's unbelievably still climbing
trees and sitting on my roof. If anyone has a clue why he is
(suddenly) acting out in this manner - please fill me in.
If you could see this cat asleep - he lays on his back with
all his 3 legs spread out sleeping & seems to have zero
discomfort of any kind. I am stumped. I did put some
chapstick in with some fancy feast the other day for
his hairball treatment. THAT wouldn't cause anything.
He gets TONS of attention, catnip, brushing, etc.
WHAT IS GOING ON - THE 2 OF THEM ACT LIKE THEY
WANT TO KILL EACH OTHER !!