How to Determine the Sex of Your Axolotl

This image shows the difference between a male cloaca (top) that bulges from the sides and a smaller female one (bottom) that only protrudes directly downwards.

Introduction

Do you own an axolotl and are unsure whether they are male or female? Look no further! In this brief article, we will explain exactly how you can know the differences between sexes in axolotls.

The most important thing to know before trying to figure out the sex of your axolotl is its age. This is crucial, since all axolotls will appear to be female until they have reached a certain age. Due to this, female axolotls should not be definitively sexed until they are roughly 18 months old!

This is usually in regards to a male who is possibly not showing an enlarged cloaca until later than average. Typically, males will start to show an enlarged cloaca around 8-12 months old, and from there it will be very apparent that they are males. However, there have still been cases of late bloomers that did not start to show until they were around 18 months old!

Cloaca

That being said, the main indicator that can decisively indicate male or female will be either the presence or absence of an enlarged cloaca (the region right below the base of the tail). A male cloaca will also bulge from the sides of its body, which will be more visible when looking directly from behind the axolotl.

This is a female/not old enough to be sexed cloaca. A small bump is a NORMAL cloaca for female or juvenile axolotls. Photo credit: rocket_sn1pez on Discord.

One of the most common mistakes is assuming that the female cloaca is a male cloaca because you can see a small bump. The cloaca in general will always be a small bump in any age of axolotl, which will point a downwards on the axolotl's body. Seeing a small bump behind your axolotl's back legs likely just means a normal cloaca, which could either mean it is a female or it is still too young to be sexed.

A male cloaca will bulge outwards from the sides of the axolotl, and may be most visible from behind the axolotl when it first begins to develop. This axolotl was an early bloomer who began to show at 6 months old.

The male cloaca may be best viewed from behind to see if it bulges from the sides of the axolotl’s body. This may also be viewable from a top view, where the cloaca may be seen protruding from the sides of the axolotl as well.

Body Shapes

The second indicator, which is far less accurate considering that size and weight can vary among axolotls, is their body shape. Female axolotls on average have a plumper body with a shorter tail, while males are typically more slender with a longer tail. Again, males can start to show late, so do not rule out the possibility of being a male until they are at least 18 months old!

Male axolotl (top) compared to a female axolotl (bottom). Differences in body shape can also be seen in these specific individuals.

This image shows the difference between the average male and female cloaca and body shapes. The male (top) shows an enlarged cloaca behind its back legs, as well as a straight and slender body shape with a long tail. The female (bottom) shows only a small bump as her cloaca, as well as a more rounded body shape. However, body shape can vary, and it is possible for male axolotls to have a more plump appearance as well.

Accidental Breeding

Another main focus of this article is to prevent accidental breeding. Properly identifying your axolotl’s sex can prevent the need to cull accidental egg clutches due to inbreeding, unknown genetics, or inability to care for potentially hundreds of baby axolotls, plus the tax that breeding puts on the female axolotl. 

We do not recommend housing juvenile axolotls together until they have been definitively sexed. Without knowing their sexes, it is likely you will end up with an accidental clutch as soon as they reach sexual maturity, and will also need to immediately separate the axolotls. Although we recommend not to house axolotls together in general, due to high risk of injury, if one does house more than one axolotl together, then the best practice would be to house any juveniles separately, or purchase 18 month and older axolotls, which you can already properly sex.

A Final Note

It is very common for axolotls to be sold under the pretext of being male or female while they are still juveniles and too young to be sexed yet. Remember, if the axolotl is not at least 18 months old, then we cannot say for sure if it is female! We strongly recommend referencing this guide to check for yourself before purchasing an axolotl.