I'm not sure their title, or how they became one. I'd recommend you research different Animal Documentarians Biographies and see what degrees they have, how they got into the career, what they do in there off time, etc.
some degrees or classes you might want to look into are:
Wildlife/Exotic/Zoo (biology, care, ecology, conservation, education, etc)
....Since 2000, Jeff has partnered with Animal Planet and Discovery Communications as host and executive producer of THE JEFF CORWIN EXPERIENCE. He also serves as the executive producer of the new series CORWIN'S QUEST. His first book, Living on the Edge: Amazing Relationships in the Natural World from Rodale Publishing, is now in paperback.
When not in the field, Jeff lectures on wildlife, ecology and conservation to audiences across the United States. Jeff also established an interactive museum and environmental education center called the EcoZone. ....
....Jeff has bachelor of science degrees in biology and anthropology from Bridgewater State College, and a master of science degree in wildlife and fisheries conservation from the University of Massachusetts at Amherst....
David Frederick Attenborough
Born 8 May 1926, the younger brother of actor Lord Richard Attenborough. He never expressed a wish to act, and instead studied Natural Sciences at Cambridge University, graduating in 1947, the year he began his two years National Service in the Royal Navy.....
At age 18, Marty traveled to Alaska on his own with an 8mm movie camera. He became trapped by snowfall in a remote valley, but survived by hunting and trapping local wildlife. He returned home and with the warm reception of his unsophisticated movie of his adventure in the north, decided to pursue a career in wildlife documentary making. In 1970, Marty graduated from the University of Arkansas with a degree in English. From there he traveled to Africa to film a new documentary. While in Africa, he was confronted with massive and wasteful killing of animals and returned to America with the intent to produce films that argued for nature conservation.
By the mid-1970s, Marty had produced several full length documentaries but had failed to hit upon a project that was an outstanding success. At this time, he approached the programming managers at Public Broadcasting System (PBS) about a half hour long wildlife show....
How about a wild career working with animals! We'll introduce you to dedicated people all over the world who are working with and for wildlife.
There's a small bit about the film crew for Jack Hanna
I hope the info helps you get started. Good Luck.