Chinchillas are one of the easier species of animals to sex. For females (left photo), the urethral cone will be immediately near the anus. There will only be a horizontal crease (the vaginal opening) separating these. For males (right photo), there will be no crease separating the anus from the penis. There will be empty space in between these two areas.
For sexing chinchillas, the general consensus is "If there's a gap, its a chap." Although, each animal is different. Their anatomy can be slightly unique to them; some males may have a wider or shorter gap. Some females may have a larger or smaller crease. But for the most part, every chinchilla will generally look like one or the other of these photos.
If you are having trouble sexing your chinchillas, feel free to contact us and we may be able to help!