Translation:The moose do not sleep in the morning.
While you are correct, there are differences between English and Swedish here.
If we say Moose don't sleep in the morning, we're talking about moose in general. The moose don't sleep in the morning however would refer to a specific group of moose.
When we use the definite form in Swedish such as in this sentence, älgarna, we are talking about a specific group of moose.
Moose don't sleep in the morning would translate to älgar sover inte på morgonen in Swedish. This would refer to moose in general.
This is the same in English, but it's somewhat strange to single out a single group of moose if it is a statement true of all moose and if it's not true of all moose it seems like a random observation. That said, the goal is to translate what is there, so I recognize that you shouldn't drop the article.