Re: stress before a season Hmm....interesting. Not heard anyone mentioning that. Lilly was spayed before her first season so no personal experience here :-\
Re: stress before a season Dogs do exhibit behavioural changes before and during a season. Sometimes as much as a couple of months in advance. However I've not heard of tail chasing or tail biting. That sounds like something else. Perhaps a trip to the vet is in order just to be on the safe side.
Re: stress before a season My Tatze had PMT! She was grumpy with her best friend and would back him into a corner and not let him out! (He is a male lab, her age but much bigger!) She was spayed 3 months after her first season and all PMT has gone I recommend it! I have never been happier since my 'spay'!