Another Sirius question

[cynthiaanncoe at home.com]

No: HPFGUIDX 25039

I'm still thinking about the end of PoA.  Sirius changes into a dog 
and fights off the werewolf.  Then he takes off after Pettigrew and 
runs into dementors.  That much I get.

But once he sees dementors, why does he change back into a man?  He 
knows that dementors can't see, so why not stay a dog?  In Azkaban, 
he once managed to slip past the dementors as a dog.  Changing into a 
man seems like a losing proposition from the start.

Any theories out there?

Cindy

-----------
"He was my mum and dad's best friend.  He's a convicted murderer, but 
he's broken out of wizard prison and he's on the run.  He likes to 
keep in touch with me, though ... keep up with my news ... check if 
I'm happy ... "  PoA, Ch. 22.