Home-range size of the bare-ear marmoset (Callithrix argentata) at Alter do Chao, central Amazonia, Brazil

We studied factors affecting variation in home-range size of four groups of bare-ear marmosets (Callithrix argentata) in parches of forest within a ce ntral Amazonian savanna. We determined relative use of different parts of t he home range by radiotelemetry. We estimated fruit availability monthly in transects through each home range and mapped the habitats within the home range of each group. We determined the densities of gum- and fruit-producin g trees in 18 50 x 50-m quadrats and related these data to the frequency of use by marmosets. Home-range size varied by a factor of 6 between groups, even though the study area covered <15 km(2) and included only one major bi ome. Marmoset activity was concentrated in areas with many gum-producing tr ees. Monthly range size is positively correlated with fruit availability on ly for the group with the largest home range; the other groups appeared to be responding to other factors. Home-range sizes appeared to be limited by the size of the main patch of contiguous forest available to each group. Ou r findings suggest that conservation planning that does not consider the po ssibility of large differences among primate home-range sizes may be unsati sfactory.