Ay, caramba! Your tiny, shivery Chihuahua puppy has short hair, barely enough to keep it warm in room temperature where you feel comfortable. But don't be surprised if your short-haired Chihuahua puppy starts growing long hair. All Chihuahua coats start out short, but some become fluffier than others.
Puppy Fur
When Chihuahuas are born, they have short but fluffy puppy fur that adds to their cuteness factor. This hair is typically feather-soft, covering the pup from ears to tail. By about 5 or 6 months old, your pup should start developing her mature coat, whether it turns out to be long hair or short.
Recessive Gene
It takes just the right set of parents to make long-haired Chihuahua pups. They all look the same when they're born, so it's not easy to tell which pups will end up with long hair. The long hair is a recessive gene, so puppies must get a set from both parents to end up with long hair. Not all pups from long-haired parents wind up with the right combination, so it's more common to see the short-haired variety.
Hair Loss
Long-haired Chihuahuas must endure the dreaded puppy uglies, also common in breeds such as the Pomeranian. When these dogs have been around for about half a year, their puppy coats start to fall out while their adult coats begin to come in. It's not pretty, and no amount of frilly bows can hide it. Your pup's hair might start falling out in patches and clumps, leaving areas of long hair combined with nearly bald spots.
The good news is this typically lasts only a couple of months before the adult coat has taken hold and is ready to grow longer and fuller.
Bald Spots
The same genetics that decide whether your pup has long hair or short hair can make that hair fall out. Chihuahuas are among a group of breeds, including whippets and dachshunds, that can wind up with bald spots along ears, chests, thighs and backs. These spots usually appear when your dog is barely out of the puppy stage, around 1 year old.
There's no cure for this baldness, but it's not a health problem -- it's kind of like when your dad started to lose his hair. Although the problem is common in all Chihuahuas, it's much more obvious in the long-haired ones.