Back in April of 2015, a video featuring Kijito, one of the gorillas that is held captive at the Henry Doorly Zoo in Omaha, Nebraska went viral, showing the enraged animal as it ran towards the people located behind the viewing window. Kijito clenched his fists and managed to crack the glass that separated him from the outside world.

zoo gorilla

Although this video received a lot of views around the globe, it wasn’t an isolated incident.

Apparently, there are over 100 videos online that feature Kijito and many other gorillas in the Omaha zoo charging and slamming into the windows. The latest video, which you can see below, shows a man standing in front of the glass window as a gorilla jumps into the air and slams hard into the glass.

These animals are often being subjects to taunts, which is one of the reasons they act this way. Experts believe that captivity can be very stressful for most of animals, especially big ones. When you add in the loneliness, lack of exercise, and constant exposure to taunts, the result is a very stressed and nervous animal, which can exhibit violent behavior. “In the wild, animals may roam for hundreds of miles, hunt their prey, raise their children, explore, play and enjoy complex social relationships,” says animal rights organization Peta UK. “Yet in zoos, their lives are restricted to four walls.”

The easiest way to make sure gorillas and other animals don’t end up in these situations is to stop supporting the institutions that put them there. If you want to learn more about the best ways to keep wildlife where it belongs, we suggest you check out the Born Free Foundation, an organization that focuses on the rights of animals, and tries to rehabilitate animals that have been held captive and release them back into the wild.