Question

Populations of two coexisting species are both tertiary consumers in a community. What relationship may exist between these two organisms?

Answer 1

If two species of tertiary consumers are living together in a community, there build a competition between them.  

Tertiary consumers feed on primary and secondary consumers and there is no one to feed on them hence named as Apex consumers.

If two consumer species are living together, there will be limited amount of food source which will give birth to competition and which might to lead extinction of one specie.