There are certain characteristics that most male tortoises share, but many species have a few that are unique to them. Please note: it is usually impossible to accurately sex a tortoise before it is sexually mature.
In most species of tortoises, the most common sexual characteristics are:
1. Size and color.
- Male: Usually smaller and slightly more colorful than the females.
- Female: Usually larger to allow space for eggs.Usually somewhat more dully colored.
- The male impressed tortoise shows very distinctive color changes when mating.
- Red-footed tortoises are one of the size exceptions- males are often larger at the same age.
2. Tails. One of the most helpful characteristics
- Males: Longer, with the cloacal opening in about the middle. May have a hardened claw-like tip in some species.
- Females: Very short and stubby, with the cloacal opening near the base.
- ‘Claw tips’ are seen in elongated tortoises.
3. Carapace. In some species the shape of the carapace is distinctive-
- Red-footed tortoises in the northern parts of the range show a distinctive ‘wasp waist’.
- Male hingeback tortoises are more elongated than the rounder females.
- Male Hermann’s tortoises are slightly wider at the rear than the female.
4. Plastron- Indent. Another almost universal characteristic.
- Male: Mildly to deeply indented to allow them to better mount the female.
- Female: Flat or slightly bulging to allow more room for eggs.
5. Plastron- Gular Scutes.
- Male: Some species have projecting gular scutes for fighting/flipping rival males.
- Female: Most species do not have projecting gulars.
- Some species with this characteristic include the bowsprit, plowshare and desert tortoises.
6. Plastron- Anal Scutes. (Some species. See illustration below)
- Male: Anal scutes form a ‘wide’, open angle and the points are further from the marginals to allow the tail more freedom of movement.
- Female: Anal scutes form a tighter angle and the points are close to the marginals to allow more protection
- Some species with this characteristic are red-footed, star, Sulcata, Forstens, and impressed tortoises.
Male and female anal scute angles and gaps, courtesy of Vicente Niclos, Testudines.org
Adult male Brazilian red-footed, note tail length and plastron indentation (photo thanks to ‘JD’)
This is slightly complicated by some research that shows that some long-term captive female Brazilian red-footed tortoises (and possibly some other species) show strongly masculine features and appear to be infertile.
Chelonia.org’s page of links for sexing other tortoise species