By definition, Vivarium is an enclosure, container, or structure adapted or prepared for keeping animals under seminatural conditions for observation or study or as pets; an aquarium or terrarium. The story of the movie exactly just like the definition of the tittle
THIS IS THE WHOLE POINT OF THE STORY (according to me): Alien (or whatever it is that abducted Tom and Gemma) can't raise their own offspring and need a human couple to help them to raise their own offspring just like the bird at the beginning of the story. And the bird that raise the baby bird (although the baby bird is not its child and this baby bird actually the one that killed the biological baby bird), can't do anything about it.
The whole point of the movie explained entirely in this scene when a student of Gemma saw dead birds (The one that has been showing at the beginning of the movie). This is their conversation and the meaning of the conversation and the relation with the meaning of the movie itself:
Student: S Gemma: G
S: Who did that to the poor baby birds? => this is we as an audience ask why the story punish both Tom and Gemma G: I don't know. Maybe it was a cuckoo. => this is the Story explaining itself. The explanation is at the end of the movie when Gemma hit the Yonder's Boy S: Why? => this is we as an audience ask the reason of that torture to Tom and Gemma and countless another couple in the story G: Because it needed a nest. => this is the Story explaining itself. S: Why doesn't it just make its own nest? => This is us again, asking the question G: Because that's nature, that's just the way things are. => this is the Story explaining itself. We as an audience can't complain because that's just the way things are S: I don't like the way things are. They're terrible. => This is us again, at the end of the movie, hated the Story so much. So many plot hole (you can read the plot hole at the end of this review) and so many unanswered questions make us feel incomplete when leaving the theater after seeing the movie G: Well... it's only horrible sometimes. => this is the Story UNABLE TO explaining itself. This is why the logic of the movie is so low according to me. The story can't explain it self and only stating the statement that it's only horrible sometimes
Though it's never made explicit in Vivarium's ending, the most obvious interpretation of Yonder and the strange boy that Tom and Gemma are forced to raise is an alien abduction story. The film opens with a shot of a newly hatched cuckoo pushing other baby birds out of the nest. This is a phenomenon in nature known as brood parasitism, in which some birds will lay their eggs in a stranger's nest in order to trick the other bird into raising their young. In Vivarium's opening, the cuckoo eventually becomes so large that when its unwitting adoptive parent returns to feed it, the cuckoo looks like it's about to consume the adult bird's head - foreshadowing the movie's ending.
Vivarium takes the behavior of the cuckoo and reimagines it as an alien or extradimensional species that has invaded Earth and forces humans to raise its offspring by trapping them together in a "nest" (in this case, the house at No. 9 in Yonder). Just as some female cuckoos are able to lay eggs that resemble the eggs of the bird species whose nest they are left in, the boy's species is able to imitate humans closely, but not perfectly. Tom and Gemma notice something is off about Martin as soon as they arrive in the real estate office and observe his strange behavior, and the boy's voice definitely doesn't sound like a normal human child.
Compounding the alien abduction theory is the strange alien language that appears in the boy's book and the patterns that appear on the TV, which are clearly communicating to him. At one-point Gemma asks the boy to imitate the person who gave him the book and he starts to transform, with bulging growths on his neck. Later, after she attacks him with the pickaxe, he gets down on all fours and scuttles like an animal - all of which points to him being an alien species in disguise. The impossible space that Gemma stumbles into when she tries to chase the boy at the end of the movie definitely seems like an alien construct, as does the impossible space of Yonder itself.
Based on Vivarium's ending, it seems that these aliens age rapidly, growing to adulthood within a year (the boy looks about six years old after just three months) and declining from middle age to old age within the same space of time. They sustain themselves by trapping human couples in Yonder and forcing them to raise their weird children, and when a new "Martin" reaches adulthood, he replaces the old one. The aliens do not appear to form any kind of emotional attachments to their adoptive parents, and do not grieve for them when they die
Tom and Gemma are literally stuck in this heteronormative structure of what a couple is "supposed to do" as they get older. Against their will, they have been forced into the suburban life, a home they despise, a routine they grow resentful of, and a child neither of them wanted. They are now stuck on a path for life that is both mundane and horrifying - one that ends in their deaths, with their bodies left to rot on the grounds of the house they hated. They aren't alone in this nightmare either, as the parallel worlds of Yonder reveal. This is the world that awaits us all, or at the very least, the white heterosexual middle-class couples to whom this fantasy is primarily sold to.
Interestingly, Tom and Gemma never ask out loud why they have been trapped in the world of Yonder and its restrictive rules. They just get on with it because they have to. This is partly what makes Vivarium so fascinating: It is keenly aware of the smothering expectations placed upon people to adhere to societal norms, even as they become more unattainable and less desired by younger generations. Nowadays, we are less tied up by such conventions and it's far more normal for people, whatever gender they are, to remain unmarried, child-free, or off the property ladder, whether it be through choice or financial restrictions. Still, even today, it is that image of the happy suburban white couple with children and a mortgage that dominates the world and is deemed the default mode of life. Tom and Gemma were not picked to become a new part of Yonder for any other reason than because they were there, and that makes their fate all the more terrifying. It could happen to anyone.
The most interesting and arguably the boldest aspect of Vivarium is in how it takes on the concept of parenthood. Here, to be a parent is to be forced into a one-sided parasitic relationship that will sap you of your very life essence. It is to be miserable and unfulfilled, to commit to something that will never make you happy or yield vaguely satisfying results. Tom and Gemma did not want a child but the society of Yonder demanded it, and the boy who grows in years as the days pass is unnerving, lacks imagination, and is utterly helpless without them. It's a blunt metaphor for the realities of parenting, but most stories end such narratives in a happy way, revealing how it was all worth it in the end.
Vivarium doesn't do that. This is a film with the sheer guts to position the act of being parents as potentially the worst thing one could do with their lives, a mistake they will regret until they die. That remains one of society's last true taboos and Vivarium pulls no punches with it. Even when Gemma shares tender moments with the boy, she absolutely refuses to let him call her his mother. Her dying words to the now-grown boy are just that: "I am not your mother." It's a final act of defiance in the face of a world that took everything from her, and one that verbalizes countless people's lives, both within Yonder and in the real world.
1. there's no explanation what the Yonder's boy really need actually from the human being. From the story itself, AUDIENCE ARE ABLE TO see that the Yonder's boy actually can raise its own kind. No need to established such a complicated vivarium in term of Yonder neighborhood and put a couple of human being in there in order to raise its own kind. Constant supply of food, electricity, etc., you named it. The Yonder's boy even can understand the TV channel in the other hand, the human couple that raise it, can't.
2. there's no explanation why the Yonder's boy need to be exist in our world and what is its purpose.
3. there's no explanation how the vivarium established in the first place
4. there's no explanation why Gemma and Tom need to die
Major failure in point number 1 above make the story pointless. Although as an audience we can get the meaning and associate it with our real-life condition but nevertheless, it is still meaningless.
Truman show (starred Jim Carrey) is an example of vivarium but it is elegantly explaining the plot. The story (Truman Show) reveal itself and audience feel completed when leaving the theater after seeing the movie; whereas impossible to get the same feeling after watch this so-called Vivarium.
Review by andylaode from the Internet Movie Database.