As many shelters have encountered, hoarding situations are often not limited to cats and dogs. So staff can sometimes be faced with determining housing based on sex to avoid adding to the pet population. Although some exotic species are very social and being housed together can reduce stress, it’s important to be able to sex them to prevent unwanted litters, advise potential adopters, and avoid possible fighting. Sexing different species can be challenging to say the least. Internet searches can be a powerful tool with images and videos to help. But here are some tips all in one place that may be useful:
Rabbits
Rabbits can be tricky. A relaxed male can have obvious testicles. But if nervous, they have an ability to keep them in their abdomen rather than allowing them to descend and be easily identified. If already neutered, it is essential to extrude the genitals to determine sex. There are sometimes only subtle differences between an extruded penis and an extruded vulva. It’s also important to remember proper handling techniques when sexing rabbits since any kind of a struggle can lead to a back injury. 
Guinea Pigs
Guinea Pigs are somewhat easier. Males will have obvious testicles usually becoming more prominent after 4 weeks of age. If altered, the penis can be extruded to verify sex.
Small Rodents
In some instances males can keep their testicles retracted like rabbits. Otherwise, males can have prominent testicles. Other tips include using the distance between the anus and genitals (where males will have a greater distance), and observing nipples (only in females) to determine sex.
Reptiles and Birds
These animals can be the most difficult to sex. Some species have different coloring or physical characteristics that differentiate the sexes (Eclectus parrots have red females and green males). Lizards and snakes can sometimes have sex determined by inserting a probe into the cloaca (the probe will go in further in males). Some species can only be sexed with DNA testing. It’s recommended to involve an exotics veterinarian or specialist to aid in sexing.
With Spring in the air, it may be a good time to brush up on sexing different species because you never know when you may have hundreds of rats on your hands.
