Plot-wise, the appearance of a bear puts a temporary halt to the “Whose putz is bigger?” contest between Mark and Sid. The bear also forces a halt to the Homicide Brothers’ attempt to squash Mark with a huge boulder. They decide to bail on the entire enterprise. So much for plot.
It’s interesting how characters pop in an out or move here and there so quickly. For example, where was Jeb, until now? Did Sid suddenly jump up the cliff (panel 3) or is that supposed to be a down-looking-up view? Normally, Rivera is quite good at depicting vistas and perspectives.
Mark presumes this must be a mother bear protecting her young, when Jeb already established that he is being protected by a bear. Why? How can Mark tell male from female? According to the Virginia Department of Wildlife Resources, females have more tapered faces (longer snouts); their legs are not as straight, thick, and long as males; and their bodies are more streamlined, less blocky. In short, this looks like a male to me. But I’m not about to look between its legs to verify my conclusion.