The canine ear is a complex anatomical feature, an essential pathway through which the dog perceives the world. The inner ear, middle ear and outer ear contribute to a dog's hearing and balance. The external ear is also an important aspect of a dog's appearance. Each major section of the ear is composed of smaller, more specialized parts. Although scientists and veterinarians can identify and explain most parts of the ear, few seem to know what role the "extra" flap on each dog's ear plays.

So, What's an Earflap?

The earflap, or pinna, is the visible part of the dog's outer ear. Observations of the shape and position of the ears and the way the ears are carried on the dog's head provide clues that help people identify a dog's breed or combination of breeds. Whether upright, rounded or long and floppy, the earflap is what funnels sound into the dog's long and narrow ear canal, moving it to the middle and inner parts of the ear.

Does That "Extra" Skin Flap Have a Name?

Although animal specialists disagree on why dogs possess this mysterious flap on each ear, most call it the "marginal cutaneous pouch or sac." Described as a folded pocket of fur-covered skin, the pouch is located along the caudal margin, or outer edge, of the earflap. It is formed by an indentation beneath the cartilage of a dog's external ear; however, according to veterinarian Lynette K. Cole, the cutaneous marginal pouch appears to have no obvious function.

Are the Marginal Cutaneous Ear Pouches Vestigial?

People have divergent hypotheses about why the marginal cutaneous pouch is part of the dog's ear. Veterinarian Michael Fox suggests, in his pet advice column, that these small vertical pockets, which are located near the base of a dog's external ears, might be vestigial structures that at one time had a purpose. Another hunch is that scent glands are hidden within the flap-like pouches on the outer edge of each ear.

What Do We Really Know About These Flaps?

If any academic or scientific studies of the flaps or pouches on the outer side of a dog's ears have been conducted, it appears that documentation and results have not been published. Veterinarians do know that these pouches are a favorite place for ticks to hide. During certain seasons, mites may burrow into the marginal cutaneous pouches and cause pain and intense itching. The ASPCA recommends that you regularly check your dog's ears, and ask your veterinarian to show you the safest methods for keeping all parts of your companion's ears clean and healthy.

Remember to Take Care of the Whole Ear

When examining your dog's ears, do not forget to look inside the marginal cutaneous pouch. Dirt can gather in the creases, and irritating insects might hide in the shallow pockets and make your dog extremely uncomfortable and agitated. Ear scratching can lead to ear damage, such as torn skin at the edges of the ears, external bleeding or a hematoma, which is bleeding between the skin and cartilage of the earflap. Use an ear cleaner when cleaning your dog's ear and be prepared for him to shake his head sending droplets into the air. Use care not to stick anything inside your dog's ears. Consult your vet or have your groomer clean your dog's ears if you're unsure how to do it.

By Maura Wolf