Understanding the molera or fontanelle in the Chihuahua

Chihuahuas are really popular tiny toy dogs that are petite enough to thrive within even the smallest of homes, but that have the personalities of much bigger dogs! The breed as a whole tends to be prone to good health despite their small, delicate size, but if you own a Chihuahua or are considering buying one, there are some unique breed traits as well as potential problems that you should be aware of nonetheless.

One of the most interesting things about dogs of the breed is that they are often born with a molera, or fontanelle – a gap or hole in the dog’s skull that you can usually feel with your fingers as an open or soft spot. The molera doesn’t appear in every dog of the breed, but it does across a significant number of them – and very commonly, the molera will close up on its own as the dog gets older, although this is not always the case.

If you own a Chihuahua or are considering buying one or even breeding from your own dog, it is a good idea to understand the basics of the molera, how to identify it if it is present, and the potential implications that it may have for the dog. Read on to learn more.

What is a molera?

A molera may also be called a fontanelle or soft spot, and if present, it can be found located where the skull’s frontal and parietal bones meet. This spot is a few inches higher than the middle of the dog’s nose, towards the top of their head. The spot itself can be hard to find if you don’t know what to look for, as it is usually very small – up to an inch across at maximum, and often a lot less. The hole itself tends to be either round or diamond-shaped, and may have clear, smooth edges or slightly uneven ones.

Whilst this hole is referred to as a molera in Chihuahuas, it can be found in other animals too – including some other dog breeds, and baby humans too! Outside of the Chihuahua breed, the hole is usually known as a fontanelle.

How many Chihuahuas have a molera?

Historically, the Chihuahua breed standard specifically cited the molera as a breed trait, although The Kennel Club’s breed standard no longer contains any reference to its presence or absence.

It is largely accepted as something that is present within a lot of dogs the breed, but it is not something that is deliberately bred for or viewed as desirable, although it is by no means necessarily harmful to have one either.

Smaller Chihuahuas are more likely to have a molera than larger dogs, as are those with exaggerated apple heads. The molera is very common across the breed as a whole, with most pups of the breed born with one, even if it closes up very quickly as the pup gets older.

Does the molera close up?

In a lot of cases, the molera will naturally close itself as the pup gets older and the bones fuse together. This generally happens within a few months of birth, but can take up to 18 months in some cases – and some Chihuahuas born with moleras will always have a small gap or soft spot that never closes.

Your vet can confirm whether or not your pup has a molera, and regular check-ups will help them to ascertain whether it is getting smaller and when/if it closes entirely.

Do moleras cause any problems?

The molera within the Chihuahua breed is not seen as a flaw, and rarely causes problems for dogs of the breed as long as their owners are aware of it.

However, whilst a molera is present, it does mean that there is a weaker, unprotected area on the dog’s skull that is particularly fragile and at risk of injury or damage if the dog hits their head or otherwise hurts themselves. For this reason, it is wise to work out whether or not your own pup has a molera, and check over time if it is closing. In the meantime, it is important to be careful to keep your Chihuahua safe from bumps and accidents (without wrapping them in cotton wool!) and ensure that if they do take a tumble or hit their heads, they are checked out by the vet immediately.

Historically, a connection was made between the presence of a molera and a predisposition to a condition called hydrocephalus, or fluid on the brain. However, more modern research has proven that the presence of a molera is not connected to the development of hydrocephalus – although the latter is a known breed-specific health issue that Chihuahua owners should also be alert for.

Additionally, epilepsy is another health issue that can be found in some Chihuahua breed lines, and dogs that suffer from fits are at higher risk of harm from the presence of a molera because they might hit their heads when fitting, so you must take steps to support and protect their heads if they undergo a fit.

If your puppy or adult Chihuahua does have a molera, it is important to let your vet know, so that they can monitor it and provide you with advice on caring for your dog and keeping them safe. Owning a dog with a molera doesn’t have to mean that the way that you care for or manage your dog should be highly overcautious, but you should keep it in mind and be careful to keep your dog safe – and avoid knocking them accidentally if they get underfoot!