Results of a 4-year study in Sangay National Park, Ecuador, indicated that the mountain tapir Tapirus pinchaque, consumes a wide variety of woody and non-woody plant taxa primarily as a foliose browser, and has a preference for some nitrogen-fixing plants. The more closed-cover Andean forest and chaparral habitats contain a greater abundance of mountain tapir-favoured food than the more open grassland paramo, riverine meadow, and pampas vegetation types. Andean forests are considered the most critical habitat for the survival of this tapir because of their provision of cover and food. Field observations and results of faecal germination experiments show that the mountain tapir assists in the successful seed dispersal of many species of Andean plants. Significant regressions between: (1) seed germination and (2) both the natural logarithm (In e) of the preference ratio and the dietary abundance of food species indicate a mutualism between the mid to high montane-dwelling mountain tapir and the plants it consumes. A significant relation during the past 2 to 3 million years is proposed between: (I) the crossing of the Panamanian Isthmus and the occupation of the mid to high northern Andes by ancestors of the mountain tapir, and (2) the rise of the Andes and formation of the montane forest and paramo ecosystems above c. 2000 m elevation.