If I've seen it once, I've seen it a thousand times: a human walks into the backyard, sees their dog digging another hole and totally wigs out. After multiple shouts of "AAACK, NOT AGAIN!" and, "NONONONONOOOOOO," there is an inevitable wail, "WHY DO YOU DO THIS?!"
Humans, I'm here to help you see beyond the patches of missing Kentucky Bluegrass and get into the mind and heart of your dog burrowing a deep hole in the ground. Let's set aside speculation and conspiracy theories and get to the real bones of the issue: dogs dig for a variety of reasons. That's why it's so confusing—one dog's cooling system is another dog's escape route. Once you understand the differences, you can understand where your dog is coming from (or maybe where he's heading, as the case may be.)
He's trying to be cool. No, literally. On a hot summer day, the ground is soothing and cool a mere few inches below the surface. A shallow empty pool of cold soil is heaven on earth for a warm body. Seriously, you should try it.
Your fertilizer is tempting him. Some organic lawn treatments and fertilizers contain cow blood or bone meal because it is a natural source of nitrogen. And while your dog loves how it smells (and tastes), it can be poisonous if a large amount is consumed. Generally it's best to keep your pets off of treated areas for 72 hours. And stop them from digging into any fertilized soil!
He's chasing tail. If your dog hasn't been neutered, the digging—particularly under fences—might be a cry for help. As in, "Help me, I'm late for my date with Sheila!" When Sheila happens to live on the other side of the fence.
There's a varmint who needs to be taught a lesson. Do you expect your dog to help protect your home from intruders? Well, according to your dog, this includes groundhogs, moles, and other dirt-dwelling imposters who will pay for their crimes just as soon as your dog can dig into their evil lairs and get his paws on them. You're welcome, by the way.
He's opened a few high-yield savings accounts. You've raised a responsible dog and he's eternally grateful for your generous gift of rawhide bone/tennis ball/squeaky toy/jingly trinket. He's showing how much this means to him by finding a spot to keep it secure. It's an honor, really.
There's a hole in his heart that goes all the way to your office. Why do you have to leave every morning after your coffee, wearing those sensible shoes and blabbering about budget meetings? Your dog misses you terribly and knows that you'd both be happier if you could just spend all day together. Sure, some may call the digging while you're away "separation anxiety," but your dog has been watching a lot of NatGeo lately and is pretty sure that he can get to you before lunch.
It's just...there. Like his forebearers who dug for prey, breeds like Dachshunds and Terriers dig because their ancient DNA tells them to. So while you may think you are observing a dog digging an aimless hole, what you are really observing is an evolutionary burp, an echo of a time long gone by.
See? A little understanding can go a long way to solve this mystery. Now you can finally set aside the belief that canine excavation is something dogs do to aggravate humans. It simply isn't true. That's what barking at invisible squirrels is for.