It is a bilateral association between different species, in which both benefit; However, such an association is not obligatory, and each species can live in isolation.
The actions of birds that promote the dispersal of plants by eating their fruits and evacuating their seeds in a distant place, as well as the action of insects that seek flower nectar and involuntarily contribute to the pollination of plants are considered examples of protocooperation.
As an example we will cite:
- Paguro snail and actinias - Also known as a hermit bernard, it is a marine crustacean that has a long, soft abdomen, unprotected from exoskeleton. In order to protect the abdomen, the bernard lives inside empty shells of snails. On the shell appear actinias or sea anemones (coelenterates), animals carrying urticating tentacles. To the paguro, actinia does not cause any damage, because it benefits, being taken by him to the places where there is food. He, in turn, also benefits from the efficient "protection" she gives him.
- Toothpick Bird and Crocodile - The stick bird penetrates the mouth of crocodiles on the banks of the Nile, feeding on food scraps and worms in the reptile's mouth. The advantage is mutual because, in exchange for food, the bird frees crocodiles from parasites.
Note: The ecological association between the stick bird and the African crocodile is an example of mutualism, when one considers that the bird removes parasites from the reptile's mouth. But it can also be described as an example of commensalism; In this case, the bird acts only by removing food remains that lie between the crocodile's teeth.
- Anu and cattle - Anu is a bird that feeds on ticks on the skin of cattle, capturing them directly. In return, cattle get rid of unwanted parasites.