Well - actually they don't perfect coil when they ovulate (at least mine haven't) - mostly I've been able to catch mine because they will lay stretched out across their tubs before and during ovulation - then when they are done they will go coil over the heat until eggs. I would suppose this would have something to do with keeping the eggs developing inside of them warm and just being in a comfortable low engergy postion. Also given that their balling is defensive position this coil may be a way they keep the developing eggs safe from natural pretators. Then again there could be no reason what so ever for it. But it would make sence that it would have something to do with heat and the eggs inside of them.
-----
Tosha 
"Nihil facimus sed id bene facimus"

11.42.0 Ball Python (Harry and Fluffy and gang)
1.0.0 Angolan Python (Anakin Skywalker)
0.0.1 Green Tree Python (Verdi - yeah I know but my kids love the book)
0.1.0 Bredls Python (Smurfette)
0.2.0 Feline (Pippen and Pandora)
0.0.1 Desert Tortoise (Pope John Paul aka JP )
2.2.1 Fish (1,2,3,4)
0.0.0 frogs rescued from pool skimmer