Final answer:
The statement is true as prey population size and predator population size are interdependent, each acting as a limiting factor on the other's growth in a continual cycle.
Step-by-step explanation:
The relationship between predator and prey populations is dynamic and interdependent. The statement that if a prey population decreases the population of its predator probably will decrease as well is true. This is because prey and predators are in a cycle where the prey population size directly affects the predator population size. When prey numbers increase, predators have more food, leading to an increase in the predator population. Conversely, as predators become more numerous, they reduce the prey population through increased predation. This, in turn, leads to a decrease in the predator population due to a lack of sufficient food resources. Such a cycle can continue indefinitely, with both populations acting as limiting factors on each other's growth.