In The Time of Dinosaurs

I reared up to my full height and took a look around. I could tell that we had run up into the mouth of a river.
The riverbanks were steep on our side of the river. My pathetically dim bear vision could barely make out some vague shapes moving on the far bank. I sniffed the air. The grizzly sense of smell is excellent. What I smelled was puzzling. <I'm smelling ... I don't know what. It's like something is missing. Like the air has been scrubbed clean. I smell various trees and plants, but. . . > I shook my huge head. <I don't know. Something I should be smelling, only I'm not>
Tobias stood up shakily on his talons. <Car exhaust? The smell of fossil fuels burning? The faint smells of backyard pools and grease-belching fast-food restaurants? The smell of human sweat, perfume, garbage? In
other words, all the smells of civilization?>
<Yeah. Exactly. You're right.> I glared at him. <Too right. How did you know? What's going on, Tobias?>
<Well, my wings and tail are a mess, but my eyes are still working. I can see what you can't.>
<You can't see smells.>
<No. But I can see that small herd over across the river. That small herd of hadrosaurs over there.>