There is a stunning variety in the shapes and sizes of heads in the dog world. There are dogs with little heads, like Yorkies. There are dogs with huge heads, like Saint Bernards. Some dogs have rounded heads, while others are almost square; some heads lead into a long tapering nose, and others have a flat face.

But all dogs have a bump on their heads. In some dogs it is more noticeable than others, but it's there. And people have noticed it for a long time. So much so that some folklore has developed around it. Even the Disney cartoon dog Pluto has a large bump on his head.

The bump on a dog's head is sometimes referred to as a "knowledge bump," a "knowledge knot," or a "wisdom bump," so it should come as no surprise that it was once thought to be an indication of a dog's intelligence. Some breeds of dogs have a more prominent bump than others. Hounds, especially Bloodhounds, have a very large bump. Since the bump was so large, and Bloodhounds' sense of smell is so keen, some believed there was a correlation between the two. Golden Retrievers, Labrador Retrievers and English Setters are other breeds which sport an exceptionally noticeable bump.

This bony protuberance has an actual name: an "occiput." It is a natural part of a dog's anatomy and is there for a couple of reasons. Its primary purpose is to protect the bones of the dog's skull and, in turn, his brain. Predators would often try to crush a dog's skull, so the more protection the skull had, the better the chances of survival for the dog. 

The other use it serves is to assist the dog's head movement in relation to the spine. The bump is also the home of several nerve endings. Some who practice therapeutic canine massage and acupuncture believe this area of a dog's head is worthy of extra attention.

Although the existence of an occiput is necessary and natural, any change in the appearance of it can be a red flag. Since it protrudes, it may get bumped. If the blow is hard enough it can cause a bruise, which can make the area appear larger than usual. Muscle atrophy can also cause the bump to appear more pronounced. 

It's important that the underlying cause of muscle loss be discovered and treated, unless it is due to old age. As adolescent dogs mature, their bump can become larger temporarily. Hair loss around the area can make the bump appear larger as well. If you notice any changes in your dog's occiput, take him to his vet. It could be something harmless, as in a growing dog, but it could be the first sign of a serious ailment that requires the vet's attention.

Whether large or small, your dog has a bump on his head. Keep an eye on it and watch for any changes. And regardless of its prominence, it's just one more little feature that makes your dog the dog you love so much.