It can be difficult to work out if a reptile is a male or female as often there is very little (if any) external differences between the sexes. This is in contrast to most mammals where gender determination is generally straight forward. Birds are also becoming increasingly easier to sex as we now have access to incredible DNA technology where we can tell the sex of your bird from 1 drop of blood – unfortunately this technology is not yet available for reptiles.

Many reptile owners couldn’t care less if they have a boy or a girl however knowing the sex of your reptile can help you to be aware of what behavioural and reproductive conditions they may be at risk of. A good example is if your reptile is a male it cannot suffer from conditions like dystocia (difficulty giving birth) but may be more aggressive towards other males in the cage. If you have a male python it may be more prone to brumating (similar to hibernating) and not eating for longer than a female during the cooler months of the year.

Today’s article looks at the different methods of reptile sexing commonly offered by most reptile vets in Australia.

Visual sex determination
Some reptiles have obvious sexual dimorphism where the males look quite different to the females. Many geckos are a good example of this as the males develop a much larger bulge just caudal (towards the tail) to their cloaca. Several dragon and monitor species also have external differences with the males often having larger heads, more obvious femoral pores, growing to a larger size and in some cases having larger spurs at their tail base. Some species of turtles also have external differences in shell shape and tail length with the males tail generally being longer.

In many species you can also look for a ‘hemipenal bulge’ which is a tubular bulge that runs towards the tail tip for a short distance on both sides of the bottom of the tail starting at the cloaca. This bulge shows where the hemipenes (the reptile equivalent of a penis) sits and is only present in males.

Some species are able to be sexed by placing a bright light source up against the tail base (while in a dark room) and looking for the blood vessels that run inside a males hemipenes. This works well in species that are lighter in colour with a relatively thin tail however is challenging in other species.

Probing is the most common method of snake sex determination and involves placing a smooth and round-ended metallic needle into the cloaca then directing it towards where the hemipenes would sit in a male. If the probe advances only a short way then the snake is a female as there is no hemipene for the probe to advance into.

There is a lot of potential to cause damage if this technique is done incorrectly and because of this it should only be performed by someone with an appropriate level of experience and training.

Popping involves placing a small amount of pressure at the tail base to evert the hemipenes (if the animal is a male). This technique also has the potential for harm so please do not attempt this unless you have experience.

Radiography (x-ray)
Radiography can help to determine the sex of some lizard species (and any species if they have eggs present). One method that is often used in large monitors involves plain radiography where we are looking for the ossification of the end of a males hemipene. This technique has its limitations as if this is not present it doesn’t guarantee that the animal is a female as many males do not have hemipenal ossification.

A second technique commonly used involves inserting a small amount of specialized dye into the reptile’s cloaca in a caudal (towards the tail tip) direction. The distribution of the dye looks different in males and females which allows us to determine the gender. This technique is particularly handy for bluetongue species.

An ultrasound can easily determine a reptile’s gender and can also help to tell if the reptile is reproductively active. It is non-painful and can be performed in most species that are large enough (some really small species are just too small to get accurate results).

Many reptiles can also have their gender determined by inserting a small (generally 1.9mm or 2.7mm) endoscope into their body cavity to be able to visually identify whether they have ovaries or testicles. This technique requires general anaesthesia so other techniques are often preferred where possible.

As you can see there are lots of different techniques for determining the sex of a reptile. Every reptile is different so if you would like to know any more about what the best way would be for your animal then please get in touch with us.