Mort and Andy, huge growth differece.

[Jodie]

Mort, on the right, the darker of the 2, is almost 8 years old. He was my 1st tortoise, and was not kept hot and humid for his first 3 to 4 years.
Andy is 2.5 years old. Believed female. I got her as a hatchling from @Neal. She has received a much better diet, and has lived in a hot humid enclosure.
They all grow at their own rates. I am curious what opinions may be on care versus genetics being responsible for the difference.

 

[Neal]

Wow, my adults sure do produce some good looking tortoises.

In my opinion, both husbandry and genetics play a role in growth rates. Impossible to say which might play a greater influence, if they're equal, or if there are more elements to consider than just those two that might play a critical role.

There's no doubt that husbandry effects growth rates. I recall a TTPG conference talk a couple years ago where the speaker showed captive raised Galapagos tortoises (captive raised in the Charles Darwin Research Station) with wild tortoises and the captive ones were significantly bigger...I want to say they were twice as big, but I may be remembering it wrong. It was a substantial difference whatever the it was.

Still on the topic of husbandry - From time to time I will raise a leopard tortoises primarily outdoors for my own reasons. Never any I sell, but just the ones I prefer to hang on to. These will grow a lot slower than the ones I keep indoors, at a rate of less than half (e.g. after a month my inside tortoises will have gained something like 50 grams, where the outside tortoises might be in the teens). Growth is consistently slow, but I've never had an issue where they were stunted or didn't grow to be a normal adult size. In fact, one of my largest females was raised in this way (and is the mother of the one pictured on the left).

Genetics play a key role two. I will have hatchlings from a relatively small female (12 inches SCL) mixed in with my large one (18 inches SCL), and the smaller female's hatchlings will grow at half the rate of the larger female's despite being raised in the exact same conditions, same diet, etc...Barb has one of the smaller females first hatchlings and I am willing to bet it is probably not as big, or won't be as big, as the one you have. Both would have been started day 1 in high humid-set ups like we all like, given a variety of good food, and similar care.

 

[Neal]

I just realized I should have said something about sexual dimorphism. That will play a big role too, certainly with most leopards. Males of the SA variety tend to grow equally as large as females. Whereas normal types, the females tend to be quite larger.

That could be another influencing factor in your observations Jodie.

 

[Jodie]

It is very interesting. Of the trio I got from you both females are big, 3273 grams and 2613 grams. The male is less than half at 1049. The 3 were from the same clutch, were they not?

 

[Neal]

Yep, I remember that clutch well.