Posted Mar-18-2017 12:12 PM
This a theory of what might have happened and why. This may contain spoilers to the movie. Read at your own peril.
It is said in the movie that Kong's Parents, as well as the rest of his kind, were killed by the Skull Crawlers. Specifically the Big One (aka Ramarak as it is referred to by that name on the internet but I'm still trying to find where that name came from) is known to be primarily responsible for this. When the survivors come across the graveyard, Marlow remarks that those bones are all that remains of Kong's mother and father. Judging by the size of each skeleton, they do not appear to be much bigger than Kong himself. Does this mean that Kong's parents were about Kong's age when they died? I think it does.
Kong's parents were probably teenagers like Kong when they were killed. When Kong's species emerged from the underground pocket where monsters have been hiding, according to Monarch, they began to compete with the Skull Crawlers. The Kong are the lions and the Skull Crawlers are the hyenas of Skull Island. A natural predatory competition. Casualties on both sides were common. The Kong were quick to kill the Skull Crawlers while they were young and easy to deal with, while the larger adults over-powered the Kong. The Big One is the largest of the Skull Crawlers, meaning that the morality rate of the Kong before they reach adulthood is high. Ramarak was only a little smaller than Kong, yet she (the internet also says the Big One is female. I believe it. Females are usually larger in reptiles.) was easily his match.
Furthermore, both Kaiju species appear to be social animals. Kong is an ape and apes are social animals. Kong is gentle around people (unless attacked) probably because he is lonely and they are very similar to his kind. When Weaver touches Kong, he looks like he is on the verge of tears. This probably because it is his first physical contact with another being in so long that wasn't a violent battle. The Skull Crawlers are pack hunters when it suits them, preferring to go hunt alone most of the time. Should a Kong have grown to full size, which will be close to Godzilla's size (how else are going to fight?), it is likely the larger, adult Skull Crawlers will have teamed up to bring the Kong down. The battles between the warring Kaiju would have gotten so intense that before long the only ones remaining were Kong, his parents, Ramarak and the smaller Skull Crawlers.
They were so near extinction not just because of the fighting, but because of Skull Island itself. The Island is big enough to support Kaiju, but not big enough to support multiple large Kaiju. Thus why they were at war. The Kong were probably protecting the humans, not just because of a strange kinship, but probably because they were offering food to the Kong as well. Since the natives worshiped the Kong, they probably made offerings to them as well as doing other things that would give the Kong reason to protect them. Furthermore, the Skull Crawlers are pretty mean spirited. Ramarak may have went after the survivors probably because she just wanted to kill them for fun. A Kaiju that size would need much more food to support itself (remember the size of the squid Kong killed?). Ramarak even tired to eat Kong's hand because he was holding Weaver (though, that was probably an attempt at payback for taking her eye). Kong may have also protected the humans because of the balance of nature, like Godzilla hunting and killing the Mutos to keep them from reproducing uncontrollably. Kong was very calm and gentle towards other species unless angered, engaged in battle or when they are hunting. For example, Pulling the helicopter off the Sker Buffalo. The natural aggression of the Skull Crawlers made the Kong realize that they weren't just competition, they were a threat. Skull Island isn't big enough for both Kaiju and neither are heading for the ocean. Given parts of the island are filled with swamps, large lakes and rivers, both species are not opposed to swimming. But given that the Island has a plentiful supply of food, competition alone is not a good enough reason to leave.
So with nowhere else to go and not enough room to support both species at full size or avoid each other completely, the only option left was war. The strongest survived and the weakest died. Kong's parents were eventually killed by the Big One, but how? If it was just the one giant Skull Crawler, then both Kong could have beaten it together. So one of two things could have happened.
First theory: the Kong died in the same place but a different times. It is possible one parent went to gather food to feed the young Kong and the rest of the family when the Big One appeared and killed the Kong. When the first one never returned, the second parent probably went to search for their mate, only to discover Ramarak feeding on the corpse. Thus leading to a battle that the Skull Crawlers wins.
Second Theory: Ramarak wasn't alone. Ramarak is said to be the largest, however there could have been more Skull Crawlers of medium size. But given they never appear in the movie means that the medium size ones were either killed by Kong and/or his parents, or they never woke up during the events of the film. It is likely the Skull Crawlers attacked Kong's parents as a group with the Big One leading the charge. The site where they died appears to be a favored feeding ground for the Skull Crawlers, given there are the remains of many different animals and the Skull Crawlers seem to use to site to disgorge the undigested remains of their smaller victims such as humans. Kong's parents may have been passing through or on a hunt when they wandered into this kill zone. Out numbered, they fought and probably killed many Skull Crawlers. The Big One probably circled the adults, looking for weak points before striking. Eventually, numbers brought the adult down. But if they were out-numbered, why didn't they retreat? Every animal has a fight or flight instinct, Kaiju are no exception. So why didn't Kong's parents run? It's because they couldn't. Kong was probably with them. A young, defenseless baby whose parents couldn't leave alone while forging for food. Kong's parents would be more concerned for their son's safety than their own. They fought the Skull Crawlers to the death to buy Kong time to escape.
However it happened is unclear at least for now. With the prequel/sequel comic Skull Island: Birth of Kong coming in April, we won't have to wait long for the answer. Whatever the case, there are many factors to consider. The natural rivalry between both species lead to competition over food and territory. With only so much room on the island, the Kaiju were at constant odds with one another. With no room to compromise, the casualties were high, bring both sides to the brink of extinction. Kong is the sole survivor of his species and is strong enough to keep the surviving Skull Crawlers in check. Despite how much Kong may hate the Skull Crawlers, he won't try to eradicate them entirely if it isn't necessary. Most of them live underground anyways. And even if the Skull Crawler was successful in killing Kong, she would have had a new problem. Kong and the Skull Crawlers are both part of the natural ecosystem of Skull Island. If the Skull Crawlers had no competition, they would reproduce uncontrollably and gorge until the island was a complete graveyard. They would starve unless the take to the sea in search of food. But long before that ever happens, Godzilla would rise to stop the Skull Crawlers and restore the natural order before the island can be ravaged by them. But this is just a theory.