Why do dogs need toys?

One of Kelly's favorite toys, Snakey, (She likes real snakes, too!)

Kelly loves to play and I love playing with her. One of her favorite toys is the good old fashioned tennis ball. I think she'd continue chasing it for hours...that is, if I had the energy to continue throwing it! Playing is great for Kelly, and it's great for Kelly and I bonding.

In addition to tennis balls, Kelly has a basket full of chew toys, rope toys, stuffies and other toys. Since Americans spend so much money on pet products, including toys, I wonder-- Is there some value in play, or is it just purely for fun?

Why do dogs need toys?
1. Chew toys keep jaws and teeth healthy.
2. Balls and fetching toys give a dog exercise.
3. Toys keep a dog from getting bored.
4. Problem-solving toys keep a dog's mind stimulated.
5. Stuffies and other special toys can help bring comfort.

Kelly loves to snuggle with her stuffie.

6. Bonding with your dog is another benefit of toys. (Sometimes playtime doesn't even have to involve toys, but involves chasing and roughhousing. And programs such as Pooch to 5K, and also the upcoming Koly and Kelly's K9 Kamp are a few ways to get fit and have fun with your dog.)

Lots of toys to chew and chase.

Of course, it's a whole other question-- How long do the dog toys last!! 
What do you think? What is your dog's favorite toy? Does your dog rip apart stuffies, or carry them lovingly around? How many hours a day do your dogs spend playing with toys? What would be your dog's idea of The Perfect Toy?