There is a flash back in which one of the protagonists describes how his abusive father killed his dog. It is pretty descriptive. I wish I had known about it going in.
In the chapter ‘Interlude: The Arrival’, a squirrel is killed and crushed and it’s VERY graphic. You could really skip this whole chapter - just know that there’s a tunnel that all of the animals avoid and when the squirrel dies, it feels itself turning into mist and going to another place.
In Chapter 11: ‘Circles, Stovepipes, and the Strange Smell of Funnel Cake’, the rangers find a sick deer and decide to put it out of its misery. It’s graphic and hard to read; to skip it, stop reading when Fig slams on the brakes. All you need to know is Fig’s gun jammed so Nate had to shoot the deer, and Nate gets a call from Olly’s school.
In Chapter 71: ‘Better Remember, Lightning Never Strikes Twice’, they pretty vividly describe skinning a squirrel for food.