Biology is always a little more complex than expected. For example, have you heard about Ring species? https://es.m.wikipedia.org/wiki/Archivo:Ring_species_se

Biology is always a little more complex than expected. For example, have you heard about Ring species? https://es.m.wikipedia.org/wiki/Archivo:Ring_species_seagull.svg https://es.m.wikipedia.org/wiki/Archivo:Ring_species_seagull... Until orcas learn how to teleport is not probable that they would mate with another whale that will never share the same space with them at the same time. Not speaking about the different size, "culture" and language that could be an obstacle if they would eventually meet. This planet is big enough to have more than one species of orca adapted to different habitats. If you lose one, don't expect the other taking its place in the same ecosystem necessarily.