Habitat shifting by the common brown lemur (Eulemur fulvus fulvus): a response to food scarcity.

During periods of food scarcity, most primates display behavioral responses, such as dietary switching or adjustment of traveling and foraging efforts, within home ranges. In rare cases, several primate species leave their home ranges for other remote habitats to seek alternative resources; this migration-like behavior is termed "habitat shifting." Reports of habitat shifting have concentrated on platyrrhines, but this behavior has rarely been observed among prosimians. During 1 year of observation of a troop of common brown lemurs (Eulemur fulvus fulvus) in Ankarafantsika National Park, northwestern Madagascar, habitat shifting occurred twice. To understand the causes of this behavior, I examined the seasonal availability of fruit resources in the range continuously used by the troop during the year (defined as the annual range) and compared feeding activities and vegetation types between the annual range and new areas. The troop usually stayed within a 38.7-ha annual range, defined by a 95 % fixed kernel analysis based on GPS location data collected at 5-min intervals. In April 2007, the lemurs suddenly moved to a habitat 1.0-1.5 km south of their annual range and concentrated on the consumption of Grewia triflora fruits for 2 weeks. In November 2007, they visited a habitat 0.8-1.7 km southeast of the annual range and exploited fruits of Landolphia myrtifolia. These new areas were open habitats with high densities of the respective fruit species. The density of fruiting trees was low in the annual range during these periods; thus, habitat shifting to areas with different phenological productivity appeared to be an effective response to fruit scarcity. Brown lemurs are generally categorized as a nonterritorial species, and the lemurs observed here showed no agonistic behavior in intergroup encounters during range shifting. Such nonterritoriality may allow brown lemurs to shift habitats, a behavior resulting in long-term absence from their annual range.