Diet of Alouatta belzebul discolor in an Amazonian Rain Forest of Northern Mato Grosso State, Brazil

Prior field studies of Alouatta showed the highest frugivory in A. belzebul. During 10 mo between October 1999 and October 2000, we studied the feeding ecology of a group of 7–9 red-handed howlers (Alouatta belzebul discolor) in a primary forest on the banks of a tributary of the Teles Pires River, near Paranaíta, MT, Brazil (9°34S; 56°19W). The howlers used 3 types of habitat: upland (terra firme) forest, flood plain forest (igapó) and palm forest (açaizal). During 45 complete days of observation, the group fed on 67 plant species (N = 2039 feeding records) in 24 families. The 2 most used families were Leguminosae and Moraceae, with 17 species each. Fruits predominated (40–80%) in every month, except June, when young leaves accounted for 54% of the diet. Dialium guianense (Leguminosal, Caesalpinioideae) was the most consumed species. Flower (6%) and mature leaf (5%) consumptions were low. Tree bark, live and decayed wood, and woody twig monthly consumption varied from 0 to 26%, and occurred only in igapó, where they used mostly Macrolobium acaciaefolium (Leguminosae, Caesalpinioideae), Clitoria amazonum (Leguminosae, Papilionoideae) and Licania cf. canescens (Chrysobalanaceae). Our study on Alouatta belzebul discolor complements the high frugivory in A. b. belzebul and documents uncommon dietary items for the species. Although there is intraspecific variation in howler diets and new studies have shown higher frugivory for more folivorous species, Alouatta belzebul seems to be the most frugivorous howler species, in spite of its wide geographical distribution and, in this case, sympatry with Ateles chamek, a frugivore.