Yes, remarkable isn't it ? - how numerous species of marine and terrestrial lifeforms have been moving outside their natural habitats over the last 10/15 years. Just to inform the grossly ignorant, the majority of animals are restricted to specific habitats and ecosystems according to evolution, heat/cold tolerance's and preferred food supply. Thus, there are severe limitations on moving outside their known natural habitats. Movement via natural growth and hunting grounds is only possible (generally speaking) if the conditions change - for example, if the water temperature changes to suit marine migration of both predator and prey, or the air temperature changes in the case terrestrial life forms. This often has disastrous consequences for herbivorous species where the food source is fixed.
So when we observe tropical species, like estuarian crocodiles, jelly fish stinger species and other tropical marine life moving into sub-tropical waters, it means the water has warmed to above the normal temperature. It has nothing to do with natural population growth or expansion of hunting grounds. That is a trait common to humans and not animals - generally speaking.
