This is the 10146th most frequent Russian word.
белке
The word "белке" is the dative or prepositional case of "белка," meaning "squirrel" in English.
In this sentence, "белке" is the indirect object in the dative case, used to indicate to whom the action of giving is directed, which is the squirrel.
Я дал орехи белке.
I gave nuts to the squirrel.
In this sentence, "белка" is in the nominative case as the subject of the sentence, actively performing the action of hiding.
Белка спрятала свои запасы в дупле.
The squirrel hid its stash in the hollow.
In this sentence, "белкой" is used in the instrumental case (preposition "за" requires this case here) to describe the means or entity being observed.