The usual sorts of field surveys just don't work with dragons. Uh-huh, you say, thirty to eighty feet long (plus tail), flies, breathes fire, and you can't find them to count? Yup. That's right. You can't. After Old Pete opened the cages, they didn't just wander off, they disappeared. That's one of the reasons that a few people - Old Pete included - started wondering if dragons were, you know, intelligent.
Well, the mainstream scientists weren't having any of that, of course, humans are humans and animals are animals and anyone who says it's not that simple is a sentimental fool and a Bad Scientist. There is nothing you can say to a scientist that's worse than accusing them of being a Bad Scientist. They'd rather be arrested for bank robbery than for sentimentality.