jealousy

[RhndLev@cs.com]

My regular riding horse, Special, is having a little vacation due to that 
bladder infection we discussed (thank you everyone!).  So, I've tried riding 
my young filly Knightmare, that I mentioned being afraid of riding a few 
months ago on this list (again, thanks everyone for the advice on that too).  
I have really worked with Knightmare on de-spooking her and getting her 
accustomed to me petting and messing with her from her back and a friend has 
taken her on several trail rides.  So, Saturday, a friend came over with her 
trailer, I got out my saddle and bridle and laid them out and went to catch 
Knightmare.  

Special, however, had other ideas.  When she saw the trailer, she began 
yelling at me and pacing the fence line.  Special is a BIG mare and head of 
my herd.  When she realized I wasn't going to take her and was trying to 
halter Knightmare, she attacked Knightmare and started chasing her and biting 
her.  Then, she'd come back to me and try to stick her head in the halter.  
When we came back from the ride, Special proceeded to once again chase and 
punish Knightmare.  

Is this weird or has anyone ever heard of a horse being jealous of another 
horse being ridden?  I feel badly for Special and I'm not going to stop 
riding her, but the ride with Knightmare went SO well, I definitely want to 
start riding her more.

Rhonda