This looks amazing but expensive
Learn to Become a Game Ranger by training whilst on a gap year in South Africa
Also, something which appeals is to get in touch with national geographic and ask about current projects, you could ask for a voluntary job, do training at the same time and work your way up, tons of people start in the voluntary sector unpaid...
The jobs they have advertised seem mundane and boring but you could always enquire about something more interesting like photography and offer your services for free (and do some training at the same time)
National Geographic Jobs, Careers, Employment