The phrase "ape territory" refers to the area where apes live and consider their own. It's like their home or habitat where they feel safe and comfortable. Full definition
His verbal skills are put to good use when a small group of humans, led by Malcolm, accidentally wander into ape territory seeking a dam that could restore power to their struggling community. (waytooindie.com)
Unfortunately for them the dam is located deep in ape territory and neither side is happy about it. (nerdlocker.com)
Among the humans, a fuel crisis sends the former architect Malcolm (Jason Clarke) into ape territory outside San Francisco, where resuscitating a hydroelectric dam is his community's last hope to restore power. (telegraph.co.uk)