This lean, mean, destroying machine is the monster looming over the poor little burrowing owls.
And after the incident with the snakes, Chuck Muckle reminds us who would win in the battle between beast and bulldozer:
"Can they kill a bulldozer, too?" (9.108)
That's all he has to say for Curly to understand that this machine stops for no animal.
But the "steel hulk" (18.40) is more than just a construction vehicle. This machine symbolizes the destruction of the environment as a whole. While Mullet Fingers mourns for his disappearing home, Roy reminds us that, "Same thing happens everywhere" (14.113).
Roy takes the power of a bulldozer to the next level and remarks how even a mountain couldn't stand in its way. Ultimately, the only way to save the burrowing owls (and all animals) is by stopping the bulldozer in its tracks.
Couldn't a shovel also destroy the environment, you ask? Sure, but not on the same scale.
Technically a bulldozer and shovel achieve the same goal (digging stuff up). But a shovel is like a paper airplane while a bulldozer is like a Boeing 747. So, you know, slightly different.
In Hoot (and real life) bulldozers are inanimate objects. And it's not like there is some black magic floating around Coconut Cove to make these bulldozers come to life. It's the people behind the bulldozers who are the real threat. These bulldozers represent all the people and companies who completely disregard the negative impact their actions (and construction) have on the environment.
Think of the burrowing owls, y'all.