Calf scared of another calf??

I don't know if any of you have ever experienced this but it was a first for me.  Last Saturday I put our little Hard Core heifer(5 days old) in a 12X24 pen with our JPJ heifer calf(30 days old) while their mothers  were out in the lot.  The older(and much bigger) heifer was terrified of the smaller heifer.  She tore around the outside of the pen, was bawling, etc. and tried blowing a hole through the corral panels  every time the younger calf even moved a muscle. The first time the younger heifer bawled for her momma the older calf just about went into orbit.    They were together for 3-4 hours and even later while the little heifer was laying down and sleeping the older heifer was at the far corner of the pen on full alert.  Its been my experience that, usually, calves are kind of curious about one another and  seek each other out.  It was actually kind of funny but it made me wonder why she would act that way.  Any ideas??

Are you sure it wasn't you that she was scared of? Or could it be the older calf had heard some of the momma cows talking about some of these scary clubby genetics?  haha.

You know, JIT, I think she was scared of me---she heard I'd been hanging around with some Canadians!!!  Ha, Ha!!

Actually, what was funny was that she would run behind me for protection every time the other calf as much as twitched.  I turned the smaller calf and her mother out with the other cow/calf pairs last night and the older heifer again tried to tear a hole in the fence getting away from the younger heifer.  I wonder if color has something to do with it.  The younger heifer is an ink black heifer and the older one is a red shorthorn.  Perhaps her mother told her not to hang out with those darker, clubby types.  Ha, Ha!! 

She is still avoiding the other heifer today--which ever end of the lot the younger heifer goes to the older one goes to the other.  My only thought is perhaps we've had a feral dog or coyote or something that's been chasing her and she equates the black calf with being chased.  Its still kind of a mystery.  The raccoons that show up every night to mess up the shed, the turkeys that come around every day to clean the feed bunks, and the deer that have moved in to help utilize our hay bales don't seem to bother her so I really don't know what's going on.

Like I said, its actually kind of funny(well maybe not to the heifer) but it just makes me wonder why she reacts so much.