Squirrels gather as many nuts as possible and bury them to prepare for winter. which type of behavior is this?

The correct answer is fixed action pattern behavior.

Explanation:

A fixed action pattern refers to an instinctive behavioral response initiated by a very particular stimulus. Once initiated, the fixed action pattern behavior cannot be ceased in the midway, it is performed till the end. The behavior is generated by a neural network called the innate releasing mechanism.  

The fixed action pattern is stimulated in reaction to an external sensory stimulus called in the term of animal behavior as a sign stimulus. For example, the gathering of as many nuts as possible by the squirrels and burying them to prepare for the winters, no matter what the condition is an illustration of fixed action pattern behavior.  

this is a good question! i'll do some research and come back when i have the answer!