In a desert ecosystem, coyotes and rattlesnakes both eat the same type of mouse as a primary part of their diets. recently, coyotes have been hunted and killed by people, decreasing the overall coyote population. how will this most likely affect the rattlesnake population over time? it will decrease because coyotes are the prey. it will increase because coyotes are the prey. it will decrease because coyotes are the competition. it will increase because coyotes are the competition.

 It will increase because coyotes are the competition.

An ecological niche can be defined as the functional role which an organism performs in the ecosystem in order to sustain it's life. The functional roles include how an organism obtains it's food, type of food eaten by the organism, type of habitat chosen by the organism and type of breeding season used by the organism.

In the given situation, both coyotes and rattlesnakes are dependent upon the same ecological niche that is they are dependent upon mouse as a primary part of their diets. As, both coyotes and rattlesnakes are dependent upon the same diet there may exist the competition between the two species. But it is mentioned that the coyote population is decreasing therefore the population of rattlesnake will most likely increase as the competition for the same diet decreased.  

true, i don't really know what you're asking but from the info you provided im guessing the answer is true.