Knife-wielding gorilla
One of the most high-profile mishaps at the Calgary Zoo, however, was a non-fatal one.
In 2009, a gorilla keeper inadvertently left a knife in the animals' enclosure, which one of the gorillas picked up and played with, appearing at times to brandish the weapon menacingly.
Barika, a gorilla at the Calgary Zoo, holds a knife accidentally left behind by a zookeeper in this photo taken in June 2009. (Heike Scheffler)
The bizarre scene was photographed by a zoo visitor and made international headlines.
The zoo later described the incident as being "overblown" and noted that, despite the appearance of the photos, gorillas don't understand the concept of using tools as weapons.