I don't know. Maybe they are, up north, but I live in Stockholm. The main danger animal on the roads of Sweden are moose, I'd say. Dangerous not because they're particularly violent but because they can weight up to 500 kilos, and that weight will fall down on the driver and passenger in the event of a collision.
I know, you can do the same in Swedish too. We do it a little less often, but still, you should translate it the same way in this course. You could say Du såg renen? as a question in Swedish too. If you're not sure intonation is enough, you can add a Så … at the start, just like you would with So … in English.
It makes sense that you guys would want us to use question order, plus the two questions can be used a little differently, where "Did you..." order is the default phrasing and the subject-first order is a bit more particular (or more slangy).
Like in this example, if you're asking someone if they saw a the reindeer just in general, you would say "Did you see the reindeer?" because you don't know if they did or not. You could also ask "You saw the reindeer?" as a slangy or quicker way to ask as well, and it's more colloquial to say it this way if you are specifically looking for confirmation (which is the sense that "So you saw the reindeer?" gives as well).
But, if someone had already told you that they saw the reindeer, you might say "You saw the reindeer?" if you were surprised or if you were skeptical. In this case replying to a sentence like "I saw the reindeer!" with "Did you see the reindeer?" would be a little strange and redundant because the person has already said that they saw it.
Does Swedish make this kind of differentiation too? Or do you just use the same word order for both questions and just change the stress of the sentence?
(I mean, obviously there are more response options that can be phrased as question like "Did you, eh?" which I find hard to explain the context for so I hope people know what I mean because it's a little different than "Did you, now?", or you could say things like "Did you see the reindeer?" which has a "But did you really?" sense to it where you're getting the other person to doubt their recollection, and it would be cool to know how you would convey these questions in Swedish too.)
Your reply is a bit long so I'm not sure what exactly what you're asking, but if it is "Would you say 'Du såg renen?' to express doubt/surprise the same way you'd ask 'You saw the reindeer?' in English?", then the answer is yes.
As for a way to say "Did you, now?" in Swedish, I don't think there is a neat translation for that but I'd translate it as "Verkligen?", which pretty much means "Really?", or possibly "Det säger du.", literally "You say that.", which is pretty much equivalent to the English "You don't say."