Why do dogs bury bones?
This is a habit that appears to be a throwback to our canine companions' less housebroken history. In the wild, many animals kill prey that is larger than they can eat in one sitting or even in one day. So, instinctually they will try to 'save' something for the next day or days. However, as the wild was full of predators--it wasn't always easy. Animals such as, hyenas, jackals, vultures and other scavengers are quick to move in on any unfinished prey, sometimes even before dinnertime is finished. As a result, many animals get their meals to go--eating them high in a tree, in a cave or at somewhere hidden away. Those animals that can't climb trees or who lack hiding places will bury their food--a habit that has followed even domesticated dogs to this day.

Why do dogs eyes seem to shine at night?
Dog's eye's (along with some other nocturnal animals) shine because of a special iridescent layer called the tapetum lucidum, behind the retina and around the optic nerve, that acts like a mirror. Light passing into the dog's eyeball bounces off the tapetum lucidum, giving the animal the ability to reflect (within its own eye) what little light is incoming, thus allowing it see in near darkness. The eyes shine at night because that's when the pupils are dilated wide enough for the tapetum lucidum to be visible. Humans' eyes don't shine because they don't have a tapetum lucidum.

Why do dogs turn in circles before lying down?
If you remember the first question...about why dogs bury bones, this answer is similar. Back when dogs lived in the wild, their natural instinct before lying down on their bed was to 'stamp' it down and make it more comfortable. In this way the grass would become matted and would make a cozy sleeping place.