Reptile & Amphibian Forums

Friends have told me that anal fork ratios can be used to sex various types or star tortoises.

1. I'm wondering what other types of tortoises can be sexed using this method?

2. Also, based on general experience or records, at what age does this method of sexual determination become relevent, (at what age or size does it work)?

Def:
Anal fork ratio (AFR), the ratio of anal fork to anal notch.
Measure Anal notch in head to tail direction and Anal fork across side to side.
AFR = (Anal fork)/(Anal notch)
Female AFR are less than male AFR
Female AFR < 1.7

I don't know that there is any kind of standard for each species although I don't see why it couldn't work with certain species.

The big problem is that most growth that you get from animals in captivity usually does not match that of the growth you would find in a free range animal.

There's this new book on Aldabra tortoises that sort of addresses this issue because some tortoise are classified based on shell morphology. In the case of the Aldabra tortoise there are some large populations that are basically captive raised. The issue is the question if the morphological differences are due to dietary/environmental controls or genetic controls.

I would think you would have the same problem with your question if we were considering the captive population.

On the other hand if we could develop a database with hatchlings and correlated it with the same data provided when they grew up to become adults we might be able to use it then.
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Ed
Tortoise_Keepers-subscribe@yahoogroups.com
Trying to keep the fun in Chelonian care

It would be great to start a database to collect data on growth (weight, SCL, feeding schedules and choices) and anal notch development / sexing.
I personally keep very good records of all of the above (since I only have 4 redfoots that's doable) and would love to compare my observations with other peoples'!

How could this be done? Do you know anybody who could set up a webpage to do this?

Gaby

I also keep good records but just started recording AFR a couple months ago. I agree that it will be good to share records but I'm not up to building a web site at this point in time. I'll have to post my findings when I have more data.
jbly