I guided for six years in ID and MT. No critter shouldn't mean no tip. Keep your knives, your guide has plenty of those, unless it truly is something special that he admires. Most tips for me were between 100-400 bucks. Don't forget the packer. While you and your guide are hunting, he is bringing in YOUR gear, stocking your tent with wood etc. DO NOT FORGET THE COOK!!! Give what you can. We make pretty crappy wages, considering the hours worked. Before I guided, I campjacked/packed. A fifty spot was awfully welcome.