A bird enters the mouth of a crocodile and feeds on parasitic leeches. The bird gets food and crocodile gets rid of the blood sucking leeches. Both the partners can live independently. Such an association is:
Protocooperation is an interaction between two living organisms of different species which is mutually beneficial, but both organisms can survive successfully without the relationship. In the aforementioned relationship, the bird feeds on the ectoparasites in the crocodiles mouth. The bird gets a meal and the crocodile gets rid of its parasites, but nevertheless its not an obligatory relationship. Both the organisms can survive without this relationship, therefore this relation is protocooperation.