I found it incredibly distracting to see the amount of animals out and about that would never roam so freely in daylight, let alone with humans about! Possums, wombats, echidnas, wallabies, diamond pythons, a family of ducks (???), etc. I live on a property and I am lucky if I ocasionally spot a wombat or a wallaby very early in the morning. Let alone such a menagerie!
it's common today to expect more realism because we've had such good quality for the past two decades but... at the time when the earthing was made the bar was still quite low and people didn't care so much about super realism with details like the ones you pointed out. viewers' suspension of disbelief was there anyway even if the authenticity was a huge stretch. back then realism was not a priority and audiences 'gave a pass' to what would truly look silly to us today.
not sure how old you are but...
movies in the 70s and prior were not as realistic as what we see today. the 80s brought improved realism in film but 'the earthling' came out just after the 70s when many directors still worked in that earlier "TV MOVIE" style of lame realism. (i noted this same point recently while re-watching one of my favorite shows 'magnum PI' ...i was like "damn this is so silly and unrealistic" but i remember that at the time, early 80s, it was considered the BOMB with audiences lol)
anywho, this is my guess as to why they didn't probably take great pains with the animals
when i watch stuff from the early 80s and backwards i always take this into consideration
"As the day hits the night we will sit by candlelight, we will laugh we will sing..."
I think you've both missed the point of those scenes. The ending is clearly a metaphor. It's also something that most non-Australian viewers miss. You are both right in pointing out that the wildlife shown is grossly out of place. Nocturnal animals appearing in broad daylight. Many animals in the wrong environment - to the extreme in some cases. Species that would never be seen near each other, let alone near people.
The extreme 'unreality' of the final scenes is not related to the era in which it was shot. Most non-Australians would probably not realize how completely removed from reality that mingling of animals is. There is another level to this film that most people, unfortunately, miss.
Think back to those archetypical scenes of paradise that you find in Jehovah's Witnesses leaflets, for example, and then watch those final scenes again. Foley didn't go back to the hidden valley of his childhood to die; he has gone 'home'. He has already died. He's in paradise, at last. Just substitute a diverse and normally incompatible array of Australian animals in an idyllic setting, for the mingling of lambs, lions, and people in a classic Biblical paradise scene.
With this in mind, try watching the movie again. It will of course be harder for those of you who are not very familiar with our animals and landscapes. But as Foley gets further away from civilization, the landscape gradually changes from a typical (and accurate) bush setting, to more and more scenes where the wrong species of plants and animals are brought together, culminating in the final crowded scenes of the old homestead, where everything is wrong and exaggerated. Paradise, or perhaps the Garden of Eden.