The cloaca is a multi-purpose opening located at the base of the tail, just behind the hind legs. Unlike mammals, which have separate openings for reproduction, urination, and defecation, axolotls (and many other amphibians) use the cloaca as a single exit point for all three.

Inside, the cloaca connects to the digestive tract, the urinary system, and the reproductive organs. This means food waste, urine, and reproductive cells (eggs or sperm) all pass through this same opening. Externally, it often looks like a small slit or bump, but in males it can become more prominent with age.

Because it is tied to several body systems, the cloaca can tell you a lot about your axolotl’s health and even its sex.

The Role of the Cloaca

The cloaca has three major functions:

I. Excretion of waste – Axolotls release both solid waste (feces) and liquid waste (urine) through the cloaca.

II. Reproduction – During breeding, males release sperm packets (spermatophores) through their cloaca, while females lay eggs that pass through theirs.

III. General body function – The cloaca also plays a part in balancing fluids and salts in the body, since urine exits through it.

Cloaca Appearance: What’s Normal and What’s Not

When I first got my axolotl, I was constantly worried whenever I noticed any changes around its cloaca. At the time, I thought something was wrong—until I came across a few forums like this and realized many other axolotl keepers shared the same concerns. Over the years, I’ve learned a lot through research and experience, and here are some of the key things worth knowing:

• Slight swelling can be normal. In males, a noticeable bulge is common once they reach maturity. This is due to the sperm ducts inside becoming more developed.

• Seasonal changes happen. During breeding season, males may show even more swelling than usual. Females generally have smaller, less noticeable cloacas.

• Redness or inflammation may signal trouble. If the cloaca looks irritated, swollen beyond normal, or red, it could point to infection, irritation from substrate, or injury.

• Discharge or visible material isn’t always bad. Feces, urine, and sperm plugs may be seen exiting the cloaca. Occasional sperm plugs in males are normal. However, unusual discharge, bleeding, or prolapse (tissue protruding) is a sign of illness.

Sexing Axolotls Through the Cloaca

One of the most useful aspects of the cloaca is that it can help you distinguish between male from female axolotls.

• Males – Mature males have a larger, more swollen cloaca that often looks like a pronounced bump behind the legs. This swelling is especially obvious during breeding season.

• Females – Female cloacas are typically smaller and flatter, making them less visible. Instead, females tend to look rounder overall because they carry eggs inside their bodies.

NOTE: Axolotls usually reach sexual maturity between 12–18 months of age. Before then, their cloacas may look very similar, making it hard to sex juveniles. Around this age, the cloaca differences become much clearer.

Health Issues Related to the Cloaca

Because the cloaca is a multipurpose opening, it can sometimes develop problems. Here are a few to be aware of:

• Infections – Poor water quality or bacterial growth can cause inflammation and redness.

• Prolapse – Rarely, part of the cloacal tissue may push outward, often due to constipation, impaction, or infection.

• Parasites – Some parasites can cause irritation or discharge.

Keeping the water clean, feeding an appropriate diet, and monitoring your axolotl regularly are the best ways to prevent cloacal issues.

If you notice persistent swelling, bleeding, or abnormal discharge, a veterinarian experienced with amphibians should examine your axolotl.

Common Behavior Linked to the Cloaca

Sometimes axolotls display behavior that seems odd but is related to the cloaca:

• Sitting with the cloaca pressed against the tank floor – This may simply be a resting position, but it can also mean the axolotl is trying to pass waste or relieve irritation.

• Frequent “pooping posture” – If your axolotl keeps bending or sitting in a way that looks like it’s trying to poop, check for constipation or impaction.

• Cloacal swelling in males during breeding season – Normal and nothing to worry about.

FAQs About Axolotl Cloacas

1. Do axolotls pee through their cloaca?

Yes. Both urine and solid waste exit through the cloaca.

2. Do axolotls lay eggs through the cloaca?

Yes. Female axolotls release eggs through their cloaca, while males release spermatophores.

3. Why is my male axolotl’s cloaca so big?

This is normal for mature males, especially in breeding season.

4. How do I know if swelling is normal or a problem?

Normal swelling is symmetrical and not red or inflamed. Abnormal swelling is usually accompanied by redness, irritation, or changes in behavior.