I did the GVI internship on April last year. For that I spent 3 months on a game reserve and another 3 months in a work place.
First thing you should know: game reserves are, above everything else, a business. There's no truly wild place in South Africa. Being the property of someone and a profitable business, it must be managed. I would say the reserve is like a zoo without cages.
For that, we need to give way to the tourists satying at the lodges, going on game drives. As I said, the reserve is a business, and a lot of wrong decisions can be made, not regarding the well being of the wildlife. What we in our time in GVI is locating everyday the lions and the semi-imprinted cheetah (which sometimes you will get out of the vehicle and go into the block to locate her on foot). We take basic data as behaviour, location and wheater conditions and type it at the computer back at base. Only the volunteer responsible for data on that specific drive will do it, though. Other activities during drive include operating the telemetry equipment, doing vehicle check before drive, operating the spotlight on the way back to base when it's already dark.
We collect data on other animals we might come across, like rhinos, elephants, buffalos, hyenas, etc. But these we do not track, so it's not the priority to locate first, coming across them only by chance or if we have time left after finding the "key" animals.
Sometimes volunteers will do other tasks such as reserve work by cleaning the roads, educational bush walks, base work (which is a rotation of volunteers to look after the base - cooking, cleaning - during the day).
As an intern, you will have some extra activities that the common volunteers don't. That would be basically for your education about the bush and conservation through game reserves. You will have a few lectures and will have to do some assignments. You will have a mentor to talk about your goals. And you will learn about tracks, birds and trees. But most of your knowledge, will come from your own effort. There as several books available at base and staff members willing to answer your questions. But if you don't commit yourself with your self education, you won't learn as much as you could.
There's three bathrooms, two of them with shower (not the best of showers, but at least there's hot water). Currently there are three dorms for volunteers. Most of the matress are very old and used and you will sleep on bunk beds. It's something you can get used to quickly, sleep in a room full of people and later on you can even miss it. Most of volunteers go to bed early, before 9, as we need to get up before the sun rise. The meals are prepared by the volunteers in charge, a pre made menu that can be adjusted to any diet requirements.
My second part of the program was spent in CROW (Centre for Rehabilitation of Wildlife) based on Durban. Even if I had all the help from GVI to get there, with tips of flights, places to stay and transport, I had to deal with the costs.
CROW has nothing to do with GVI except the booking, so I won't give the feedback of my time there here. But I got there thanks to GVI. When calculating the fee for volunteering at CROW, through GVI the value is around 4 to 5 times more. So if you're interested, I recommend booking directly with CROW and not any travel or volunteering agency.
The cost for internship or volunteering with GVI is very high. There are plenty of game reserves that take volunteers for much less. Of course I can only talk about my experience with GVI, and in general I'm really thankful that it started a 2 year journey through South Africa. In the end was definetely worth it. I will always remember my time at the reserve and cherish deeply as one of the greatest moments of my life.
I recommend this program for whoever wants to do a safari in South Africa and take good pictures while making friends and getting closer to the environment. Is a much better way to know the wildlife and also to keep yourself busy during a trip. You will have an amazing experience. It just wouldn't be my first option for an educational internship.