Once it goes down, Duke quickly heads over to the lizard's head. Partially to help Megaera retrieve that sword, and partially to force that jaw to stay open for Colin. Or maybe to talk to Colin-

"How close to the core do you think you are? It might be easier for you to cut the thing open than for us. If you can keep going." Of course, they could always start cutting from the other end of the lizard and look for the core that way-

Also Duke might be looking for any charred scrap of deer left. Gotta catch a baby lizard or two!