Will sleep during the day

Without knowing the broader context, I question the need for "will" in your sentence.

In the pet store:

Customer: I am looking for a special pet. I am awake all night, and I sleep during the day.
Salesperson: Oh, how about a raccoon, owl or opossum? These animals (will) sleep during the day. They are nocturnal animals.

Thank you both so much.

Yes, I see, but somehow the 'will' in that sentence sounds a bit strange to me. It is as if the animals will sleep during the day on occasion, or in certain conditions, for instance if they have to, or something of the sort. It is as if it is not what they do naturally.

I guess I will have to try to get used to that usage.

Many thanks.

azzYes, I see, but somehow the 'will' in that sentence sounds a bit strange to me

It is for emphasis; in the same way as "They do sleep during the day."

azza. These animals will sleep during the day. Does that mean that they do it on some days or every day?

It doesn't say for certain that either of those things happens.

azzCould the sentence be used if it is their regular, daily habit?

It could.
_________

"will" can be used to indicate typical behavior.