The physically undemanding Headhunters’ Trail runs from the park's camp 5 for 11km in the direction of Limbang and is an overland alternative to flying in or out of Mulu. The park does not offer guided trips along this trail, but several private tour operators do, and it's also (theoretically) possible to trek it without a guide.
This backdoor route from Mulu to Limbang takes two days and one night and can be done in either direction, although most people start at the park. After climbing the Pinnacles, it's possible to walk the Headhunters' Trail (unguided) on day three instead of returning to park HQ.
From camp 5, the Headhunters' Trail runs through the forest to Kuala Terikan, from where you'll need to take a boat to Medamit, linked by road with Limbang. If you plan to do this trip without a guide, you must arrange road and river transport ahead of time – Borneo Touch Ecotour can organise a boat and van in either direction for about RM500. If you're starting in Limbang, remember to contact the park to reserve sleeping space at camp 5.
The route is named after the Kayan war parties that used to make their way up the Sungai Melinau from the Baram area to the Melinau Gorge, then dragged their canoes overland to the Sungai Terikan to raid the peoples of the Limbang region. New roads mean that the trail is no longer much used, making it more likely that you'll spot wildlife along the way.