Two male gorillas fighting at the Omaha Zoo. This file shows clips reproduced with permission from a video taken by Shannon W. Olsen and posted on YouTube on Oct. 23, 2015. This video is particularly relevant to this study because plantigrade posture of the feet is visible throughout the sequence. Specific notable events include a forearm block used by the gorilla on the left at time 00:02-00:03 and shown in slow motion at time 00:40-00:43 and super slow motion at time 00:56-01:03. In the super slow motion clip, notice the toes of the right foot arch to grip the ground at the time of contact with the charging gorilla (01:00) and then the foot begins to spin counter-clockwise at time 01:02. At the beginning of the attack, the charging gorilla begins each hindlimb step with a heel plant. This is best seen in slow motion (00:14-00:21). Retrieved from https://www.youtube.com/watch?v=3T0z1CT-nR8.