LOS ANGELES – Katja Sutil was enjoying her visit to the San Diego Zoo's gorilla enclosure when one of the massive apes suddenly charged toward her, slamming its powerful fist into the glass and leaving a deep crack just inches from her face.

"I was really shocked. There was probably a 6-foot crack and the gorilla was just staring at me," she said. "It was terrifying."

Zoo officials said in a statement that Denny, a 10-year-old western lowland gorilla, broke one of the three layers of tempered glass separating guests from the gorilla habitat on Saturday. Denny was not injured; however, the exhibit will be temporarily closed as the glass is repaired.

"It is common for male gorillas, especially in adolescence, to express these types of behaviors," a zoo spokesperson said in a statement. "Bursts of energy, charging, dragging items, or running sideways are all natural for a young male."

Sutil said that, before charging at the glass, Denny appeared to be playfully fighting with the other male gorilla in the exhibit.

"They were really fun to watch because they were kind of taunting each other," she said. "They kept going in circles, almost swiping at each other, but then not quite hitting each other."

A similar incident took place in 2020 when another gorilla damaged a layer of glass at the zoo while engaging in a physical confrontation with a fellow ape.

Adult male gorillas are extremely strong. They can weigh between 300 and 500 pounds and are capable of lifting up to 10 times their body weight.

Sutil said she traveled from Los Angeles to visit the San Diego Zoo with her sister as a belated birthday gift and that it was a trip she would certainly not be forgetting. She and her sister ran away from the exhibit as quickly as they could after they saw the crack.

They were not aware that the protective glass had three layers, and once the giant crack appeared, they worried that Denny could easily break through if he charged again, she said.

Denny was born at the San Diego Zoo on Dec. 26, 2014, where he was raised by his mother, Jessica, and father, Paul Donn. He has several siblings including brothers Maka and Mandazzi, and half-brothers Ekuba, Gordon, Gerry and Bouendje.

Maka unexpectedly died in August at age 30 from cardiac arrest during a medical evaluation. His death was mourned by zookeepers and visitors alike, and possibly also Denny. Scientists have observed gorillas expressing grief and behavior changes after the death of a sibling or troop mate.

Gorillas are a critically endangered species due to hunting, the exotic pet trade and loss of habitat from logging and mining. Through its African Forest Program, the San Diego Zoo has focused its gorilla conservation efforts on the Ebo Forest in Cameroon, home to numerous threatened plant and animal species.

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