The exhibit was at the forefront of zoos moving away from cages in favour of more realistic living environments and adopting a range of exhibits, from natural habitats behind glass walls to jungle-like settings separated from the public by hedges and bamboo fences.
While police are investigating what happened in Cincinnati and federal inspectors are planning their own review, the zoo says it too will look at whether it needs to reinforce the barriers even though it considers the enclosure more secure than what's required.
The breach, the zoo director said, was the first time a visitor had entered the zoo's Gorilla World, which opened in 1978 and was billed as the first "bar-less" outdoor gorilla habitat in the nation.
A federal inspection less than two months ago found no problems with the gorilla exhibit, but earlier inspections reported issues including the potential danger to the public from a March incident involving wandering polar bears inside a behind-the-scenes service hallway.
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At least two animal rights groups were holding the zoo responsible for the death of the 17-year-old western lowland gorilla on Saturday, charging that the barrier made up of a fence, bushes and a moat wasn't adequate.
Most gorilla exhibits around the country now have open-viewing areas often protected by a combination of glass walls, mesh netting and moats.
Zoo Atlanta, which boasts the nation's largest gorilla collection, has several outdoor viewing spots that are designed to give visitors the feeling of being very close, but they are still separated by a series of safety barriers.