All About Piloerection — Not a Dirty Word, We Swear!

If you’re reading this, you haven’t run away screaming because we’re talking about erections today. Piloerections to be specific. It’s not a dirty word, and we’ll explain what it’s all about when it comes to our animal friends.

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Understanding Piloerection in Pets

• Have you ever noticed your cat’s sideways turn, complete with an arched back and puffed-up fur?
• Or perhaps you’ve seen a black cat with an arched back on a pumpkin, signaling the approach of Halloween?
• If you’ve observed dogs play-fighting and noticed some of the hairs on their backs standing up, you’ve witnessed a reaction known as piloerection.

Piloerection refers to the raised hairs on the shoulders, along the back, and sometimes on the tail. While this phenomenon is most commonly seen in dogs and cats, it has also been observed in other animals, such as birds and rats. This hair-raising reaction is involuntary, triggered by the nervous system. Adrenaline causes the muscles to contract, making the hair straighten away from the body.

Often called “hackles” or the “Halloween cat,” piloerection is comparable to goosebumps in humans.

• For example, whenever a bee flies past your ear and you hear that notable buzz, you might get goosebumps and feel a shiver all over.
• The same reaction can occur when watching a scary movie and a ghost appears, sometimes making you feel a chill until it passes.

Why Does Piloerection Happen?

Piloerection, or the raising of an animal’s fur, occurs for various reasons, similar to how we get goosebumps when startled. This reaction can be triggered by:

• Fear
• Aggression
• Excitement
• Insecurity
• Feeling cold
• Defensiveness
• Meeting new people or animals
• Keeping warm (especially in cats)

When an animal’s fur stands up:

• They appear larger and more intimidating, which helps to ward off predators or threats.
• The duration of piloerection varies based on the situation and the animal.
• In pets with short, thick coats or hairless breeds like the Xolo, piloerection might not be as noticeable.
• Sometimes, the fur doesn’t rise in a perfect line and may appear in patches instead.

Interestingly, not all animals experience piloerection the same way:

• Karen London, Ph.D., has observed three different types of piloerection in dogs, though scientific data on the subject is limited.
• Learn more about these types and how they manifest in different breeds.
• For example, my dog shows the first type, where the fur raises in a straight line along the back and tail.

Piloerection and Emotional States: What Your Pet Might Be Feeling

Piloerection is often a reflection of your pet’s emotional state. When a dog or cat experiences strong feelings, their body may react by raising the fur along their back and shoulders. This response can be triggered by various emotions:

• Fear: Piloerection can make your pet appear larger and more intimidating to potential threats.
• Aggression: Raised fur often accompanies aggressive postures, signaling a readiness to defend.
• Excitement: Positive emotions, such as excitement during play, can also cause piloerection, especially during social interactions with other animals.

Understanding these emotional triggers behind piloerection can help you better respond to your pet’s needs and behaviors, ensuring they feel safe and secure.

Piloerection as an Indicator of Underlying Health Issues in Pets

While piloerection is often associated with emotions like fear or excitement, it can also be a sign of underlying health issues. Some health-related causes of piloerection include:

• Infections: Certain infections can cause discomfort or pain, leading to piloerection as the body reacts.
• Skin Conditions: Dermatological issues such as allergies or skin irritations can trigger piloerection.
• Hormonal Imbalances: Changes in hormone levels, particularly those related to the adrenal glands, can result in piloerection.

Monitoring your pet for piloerection alongside other symptoms can help in early detection of potential health problems, allowing for prompt veterinary intervention.

How Should You React to Piloerection?

If you notice your pet showing signs of piloerection, here’s what you should do:

• Look around for potential triggers. Is there an unknown animal or person nearby? Is your pet angry or upset? Is the temperature too cold?
• Identifying the cause can help your pet calm down faster and relax.

For example:

• My cat often exhibits piloerection when play gets too rough, shifting into attack mode. When this happens, he needs a few minutes alone to calm down—otherwise, someone might get scratched!
• My dogs usually display this reaction when play-fighting or when new animals are nearby.

In the video below, you can observe one cat’s reaction to being scared, with the classic arched back and fluffed-up fur:

Clinical Implications of Piloerection in Veterinary Medicine

In veterinary practice, piloerection is not just a sign of emotional arousal; it can also serve as an important clinical indicator. Veterinarians may observe piloerection during examinations and consider it a clue to:

• Stress or Anxiety: Piloerection might indicate that an animal is stressed or anxious, which can affect their overall health.
• Pain or Discomfort: Animals in pain or experiencing discomfort may show piloerection as part of their response to the underlying issue.
• Neurological Conditions: In some cases, piloerection can be linked to neurological problems, particularly when it occurs without an obvious external trigger.

By recognizing these clinical implications, veterinarians can better assess and address the health and well-being of their patients.

What to Do When You See Piloerection in an Unknown Animal

When you notice piloerection in an animal you don’t know, never assume it is a safe situation. This may be the only warning you get from an animal that they are not in a relaxed state or are aggressive. Instead of trying to calm the animal or approach it, allow some time for the animal to relax. It’s usually wise to assume the animal is trying to say, “Please leave me alone” instead of forcing interaction.

Photos: Ernst Vikne (top), Violette79/Flickr

Frequently Asked Questions (FAQ)

References

• “The Genetic Basis of Piloerection and Its Potential as a Marker for Stress Response.” National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6071615/
• “Piloerection: Definition, Causes, and Clinical Significance.” RxList. https://www.rxlist.com/piloerection/definition.htm
• “Understanding Piloerection: Insights from Neurophysiological Studies.” National Center for Biotechnology Information. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5470168/