An ecologist recorded twelve white-tailed deer, Odocoileus virginianus, per square kilometer in one woodlot and twenty per square kilometer in another woodlot. What was the ecologist comparing?

The correct answer is - density.

Explanation:

Density in the ecology is the measure refers area available as living place is known as ecological density. The ecological and crude density is showing the difference in that in ecological density consist only that portion of the land is colonized by the species.

In this given comparison the ecologist is comparing the density in different portions of land for white-tailed deer, Odocoileus virginianus, and woodlot.

Thus, the correct answer is - density.