It's highly recommended to go with a knowledgeable guide from a reputable company, not only for the educational factor but for safety as well.
Jungle trekking can be a serious four-hour hike or shorter less strenuous trails, to embrace a wider clientele of varying fitness levels as well as ages.
There is trekking up to the top of the 2287 ft high Gundung Raya or King of Mountians and night walks where you often spot some of the more elusive wildlife that inhabit Langkawi.
There are several reputable nature companies to choose from in Langkawi, Dev's Adventure Tours, Jungle Walla and Fauna Flora to name a few.
The Travelfish newsletter is sent out every Monday and is jammed full of free advice for travel in Southeast Asia. You can see past issues here.