Both of my girls do it--heat or no heat. Although, Daphne (my pom) is in heat right now and she hasnt humped, Trixie on the other hand, loves her monkey-luvin' hehe
http://ladies-connect.com/girls/thump.jpg http://ladies-connect.com/girls/thump1.jpg http://ladies-connect.com/girls/thump2.jpg
(those were taking yesturday haha)