If you have ever photographed some where that attracts a lot of other photographers you will recognize this behavioral pattern. It happens all the time in Yellowstone but it could be at any national park, wildlife refuge, or any other place where photographers gather.
If there is something to photograph, photographers will be spread out across an invisible line waiting for the action to start. Then, someone always has to get closer. Usually it is because they think their camera lens is too small to do the job. They are probably right, but that person seems to think that because they have a smaller lens, they should be entitled to move up! First of all, that person is likely then to be in front of and in the shot for a great many other photographers, but secondly and more importantly, there is a REASON everyone else is hanging back – regardless of the size of their lens. If that person would stop to think, would it occur to them that everyone would like to be closer? Ethical photographers hang back because the subject needs space. How much space depends upon the tolerance of the subject. If any one photographer closes in on the subject they are likely to spook it, particularly when there is a crowd. The subject is very much aware of our presence, moving in, breaking the line, only serves to make it nervous and very likely to spook. When that person moves in they are thinking only of themselves, without respect for the subject and or their fellow photographers. That person won’t get the shot because the subject will spook, but they will get a reputation among the other photographers for being a jerk or worse. Please, don’t be that person!