Hi. I have a male tabby, Tiger, about 2 years old. He is an avid hunter. I love the wildlife in my backyard. Tiger loves it too. He has been killing birds and garden snakes. I've rescued them when I can. A bell collar does not help. I've been keeping him indoors lately to preserve lives out there. He's terribly unhappy about being an indoor cat. He howls mournfully to go out. Any tips on keeping him happy without letting him hunt?