The number of wild horses per square kilometer in a prairie is the horse populations is called

Population density of horse

Explanation:

Population density refers to the number of people (or any other living species) existing in a particular area. This reflects the quantity of a particular type of living species that exist over an area of about 1 km².

Population density is obtained mathematically by, dividing the total population of the area by the total size of the area.

In the given question, it describes the quantity (number) of wild horses that are present per square kilometer in the prairie lands. This refers to the population density of horses.