Gentoo penguins will present a mate with a pebble that they find to attract a mate. emperor penguins have a specific call and movement that they make to attract a mate. which type of isolation do these penguins demonstrate?

The answer is behavioral isolation.

Reproductional isolation is a way to prevent closely related species to mate each other. This is due to reproductive barriers which can be either prezygotic (before fertilization) and postzygotic (after fertilization) barrier. Behavioral isolation is an example of postzygotic barrier. It is based on behavior, including mating sounds and rituals. Thanks to behavior isolation, the different species (in this example gentoo penguins and emperor penguins) will have different mating rituals so they could attract only individuals of their own species, respectively.