Last year, Yellowstone saw a record number of visitors — more than 4 million — as well as a record number of vehicles entering the park.

Overcrowding has concerned park superintendent Dan Wenk for a few years now. Last year, he hired a social science coordinator to research statistics on the visitor experience for that very reason.

Like most of the country, Wenk is dumbfounded by the visitor behavior that’s prompted so many newspaper stories and Facebook posts. And it’s not just this year. Five tourists were gouged in 2015 by bison, most while trying to take selfies.

But Wenk isn’t sure if these incidents correlate with overcrowding.

“I don’t know if they are related. We’re really not crowded right now compared to what we’ll be in July, so how do you explain the people on Grand Prismatic Spring? And in July, that baby bison’s not going to be nearly as easy to put in the car,” Wenk said over Memorial Day weekend.

Wenk has served as park superintendent since 2011. He also worked at the park from 1979 to 1984. A lot has changed since the 1980s. Thirty years ago, there were fewer bison, hardly any grizzly bears and no wolves, and cameras weren’t in everyone’s pockets.