Explanation

Creating a filter: The original sentence has a comparison, so we should check that comparison. The answer choices here are largely similar and they all end in the word "mammals." The author's intended meaning is to contrast "mammals" with "kit fox." As for how the comparison is introduced, it's mostly idiomatic: "unlike" is correct and simple. (E) is therefore the correct answer.

Further notes: (C) and (D) both establish improper comparisons of the "kit fox" with "behavior" and "that," whatever "that" is. Therefore, the correct answer is (E). You might wonder whether "in contrast" is ever correct, since it's an English phrase, after all. I'd say that a state of contrast, for example as in the case of two colors next to each other or a setting on a TV or computer monitor, is one in which the differences between two things affects how you view both of them. We have no such thing here -- only a difference, which is captured perfectly by the word "unlike." The correct answer is (E).