California's Santa Cruz Island scrub jay, for example, is up to a third larger than mainland jays.
"[But they can't grow] by too much due to the often limited resources and space on any island," Kelly said.
Other species, such as the tiny island fox of California's Santa Rosa Island, may shrinka trend known as dwarfism.
In the process of growing larger or smaller, a few species may change their basic structuresbirds may become flightless, for example. But no species would grow as huge as director Peter Jackson's great ape.
"Kong is obviously not a realistic representation of an island species," said Stanley Temple, a wildlife ecology professor at the University of Wisconsin-Madison. "Primates don't often get to remote islands.
"I can think of no evolutionary advantage for an island primate to become larger than its ancestor," he added. In fact, the opposite would be more likely.
"Think about the small Homo species recently discovered," Temple said, referring to the "hobbit" species of early human (Homo floresiensis) recently found on Flores Island in Indonesia.
"Larger animals have smaller populations than smaller animals, so a population of giants on an island would be small in numbers and, hence, more vulnerable to extinction than a smaller-sized animal."
Many species are particularly vulnerable on islands because the animals have evolved in the absence of competitors, predators, and parasites and have thus lost their defenses.
Granted, King Kong is not meant to be scientifically dissected. The filmmakers deliberately changed some of their animals' anatomies.
The T. rex, for example, has claws with three fingers instead of the scientifically correct twoan homage to the original movie, in which the dinosaur had an extra finger.
But the filmmakers did set out to portray King Kong himself as realistically as possible.
"It's based on a silverback gorilla, absolutely," Richard Taylor, the head creatures designer for the movie, said in a telephone interview from New Zealand, where his Weta workshop is based.
In the 1933 movie, Kong walks around on two feet, beating his chest with clenched fists. The modern Konglike his real-life counterpartswalks on his knuckles and feet and beats his chest with cupped hands.
The new Kong, however, is shown standing straight up on his rear legs and beating his chest, something that a real gorilla can't do to the same extent.
Andy Serkis, who played Gollum in the Lord of the Rings movies, was outfitted with motion sensors to provide the movement and voice for Kong. He also, with the help of 132 sensors, controlled the ape's facial expressions.
To learn how mountain gorillas walk, communicate, and interact, Serkis studied gorillas in one of their natural habitats in Rwanda.
Like Kong, real-life male silverback gorillas are fiercely protective of their females and young. If confronted by a hunter, silverbacks may stay behind and position themselves between the hunter and the fleeing gorilla family.
Frans de Waal is a primatologist at Yerkes National Primate Research Center in Atlanta, Georgia. He says Kong appears "more humanlike than gorillalike," based on the movie previews he has seen.
"The few scenes I have seen have too much direct eye contact by King Kong," de Waal said. "Gorillas almost never stare straight into the eyes of anybody."
Then there is the distinctive gorilla odor.
"The film audience misses out on this," de Waal said. "[It] must be powerful coming from an oversized gorilla. I'm curious if the girl [played by Naomi Watts] will faint."
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