question about feral baby cats leaving their mother.

when and how do they leave their mother when they are old enough?

do they leave one by one, all at the same time, and how far do they wonder before they stop, etc? 

Usually, the mother just up and walks away one day and doesn't go back.  It varies but several factors are in play.  Such as, food source, the amount of food and the health of the mother, the size of the litter, etc.  Usually about 9 weeks to 10 weeks is when a lot of feral mothers leave.  They are getting bigger and she can no longer "hunt" up enough food for everyone plus she has taught them to hunt for themselves.  Perhaps not successfully but they learn from experience.  A feral life isn't a cushy and cozy life of a housecat at all.

oh. so it is not the babies who leave, it is the mother who leaves? 

but i thought that the mother should be the one who has been living in that particular area for a long time. so she has to find an entirely new area to live?

She doesn't leave the area but she leaves the kittens.  Sometimes, usually the kittens will stay close to eachother for a little while longer.  Not always but sometimes.  It depends on a lot of factors, some of which I mentioned.  But yea the mom is the one to walk away usually. 

She keeps them in a "nest" area and it's part of her territory but only a small part and she helps them learn to hunt or scrounge or find food but once it gets to be too much for her, she leaves and heads to another part of her territory.  The kittens may stick around or may go "looking"  which leads them to another territory.  It's all instinct really.

I don't know what's "usual". . .but my feral momma cat raised a litter before I could catch her (I finally trapped her when the kittens from her next litter were 10 weeks old). It didn't seem at all dramatic, the boys just kinda started drifting away when they were about 4 months old, spending longer and longer away from the home area. One boy I caught and neutered at 6 months, and he's still around. The other one disappeared when he was about a year old, and hasn't been back.

Her daughters hung around, and she was particularly close to one of them. I caught one and had her spayed at 6 months, the other was pregnant at the same time as her mother, and it looked like they would have raised their litters together (but the daughter was killed before giving birth ). So nobody left suddenly, she didn't chase any of them away, etc. But they all had plenty of food and resources, it's probably different for ferals who live in tougher areas.

In our experience mom left at around 3 months old, the kittens supported each other until they were around 6-7 months old, after which the males struck off to find new territories. Though we did have a brother and sister who stayed with each other a year before he died.

how do they support each other, do they share the food? do they sleep together or close by?