Every wildlife photographer needs at least one long lens because most wildlife is often at a distance and often it is best to photograph them at a distance, even if it’s possible to get closer, because the subjects will be more comfortable. There’s also the issue with proximity to dangerous animals.
A big question for many wildlife photographers is whether 400, 500, 600mm, or even more is necessary.
In a video on his YouTube channel, Adrian Cho talks about his experiences with Sony’s 400 GM lens as well as the issue of 400 vs 600mm for wildlife photography.