death in winter of baby tortoises/turtles

Question
I live in Australia (South Australia)
We have the River Murray Long-Necked and Short-Necked Tortoise (some say turtle)
Why (as pets) do they die within 6 months of getting them?
Is it to do with their fat storage and their digestive system trying to work during hibernation?
Should they not be trying to hibernate so young?

Answer
Captive hibernation of turtles is tough, no matter the species. You need to maintain the right temps and humidity- if things get too wet or dry, or too cold or warm, they won't metabolize properly. It is estimated that up to 25% of turtles in the wild may die in some winters.

I do not know the specific requirments of many Australian turtles, but you can try www.tortoise.org as a starting point.