I have not yet got a tortoise but am hoping to get a Horsfiend tortoise but was wondering do they Hibinate and what the process is for doing that eg temps etc
Yes, Russian tortoises brumate (hibernate). They should be kept below 50F but above 40F. If the temp gets down below 32F their eyeballs might freeze.
My russian tortoises live outside. When I see that they have all dug down into the ground in the Fall, I dig them up and put them in a place that will stay dry, yet be cold, safe and quiet. You can box them up in shredded newspaper.
Mine have been outside the entire winter. We have had 38 days well below freezing and one ice storm that covered thei garden in thick ice for five days. The first time temps hit 60 last week, my female was up and about, sitting in the sun all day long. That night was back in the 20's and she went right back under. I have not seen the boys, but the girl was just fine if a little sluggish. I'm hoping to see the other two this weekend.
To answer the question, you need to make sure they have plenty of room and plenty of places they can feel comfortable digging in and that the soil is nice and deep for them to get below the frost line. I like to find out where they are going under and put a box or a "hide" over it just in case. make sure it is in an area that has great drainage and does not get that wet or stay wet. You might also want to build a box and put them in it like Yvonne said.
To follow up on what Stephen (Saleama) said, it depends where you live in the world if you should let your Russian tortoises brumate outside or not. If the tortoise garden is covered with snow during the winter, it's probably ok to allow them to stay outside providing they can get below the frost line. A big layer of snow protects the tortoises from freezing.
But if you live where your winters get quite a bit of rain, you should not allow them to brumate outside. I lost almost my whole flock? herd? bale? of Russian tortoises the first year I had them because I allowed them to brumate in their outdoor pen. I had 15 or so, and after that winter I was left with only a few...maybe 4 or 5? Memory is gone. They just don't do well if allowed to get wet while brumating.
I have two. I do not hibernate mine. They stay inside during winter as they are little. (5 inches and 4.5 inches.) they are active and just as happy as ever. But here in Oklahoma we had a tornado and the next month a blizzard. So I wouldn't want them outside even if they were hibernating.
My garden has EXCELENT drainage. If it did not, I would never allow them to go under in there. I checked and double checked it by running a hose for hours, then digging deep where the water stood and filling it back in with good soil and mulch mixes. In fact, I have a sink hole that is covered with wire grateing that goes under my apartment. In 2 hours of watering and another day or two of storms, my garden was drained the next day. It makes it hard to keep certain plants alive, but it is great for the torts. If you do not have or don't know how good your drainage is, find out and until you do, do not let your torts hibernate in there.
Yvonne, the term most used for a group of Tortoises is "Creep" and Turtles is "Bale". I prefer to call my group of torts and turts a family. I have a family of tortoises and turtles!