My understanding is that this image was captured by a camera trigger that was setup National Geographic photographer (Sorry, I'm unsure the name). This has been a highly published photo by National Geographic; does this mean that the tiger should be owed all the royalties and not the photographer?
And the important part is that the photographer would have still owned the copyright if it was a human who set off the trigger.
However, imagine a person picked up his camera and took a selfie. The person would own the copyright, not the owner of the camera. The photographer didn't contribute anything artistic.
This is a monkey selfie, so it's in an interesting legal situation.
The best comparison is to abstract paintings done by elephants. Does anyone own a copyright on those?