Ring-Tailed Lemur Home Ranges Correlate with Food Abundance and Nutritional Content at a Time of Environmental Stress

In order to determine whether ring-tailed lemurs (Lemur catta) adapt their ranging and select an optimal diet at a time of food shortage, we observed two adjacent troops in Berenty Reserve, Madagascar for over 250 h. The troops, created by a recent fission, ranged through closed canopy gallery forest next to a river and open forest away from the river. We conducted the study in September–October, 2000, normally a time of seasonally low resource availability, which was intensified by damage from a previous windstorm and recent drought. To examine the impact of environmental stress, we mapped their ranging patterns, intertroop encounters, feeding patches, siesta trees, and sleeping trees. We then correlated their ranging and feeding behavior with nutritional analyses of leaves and fruit from tamarind trees located in different parts of their ranges. One of the troops, D1A, ranged farther into open forest than previously. However, the range for troop D1B and the closed canopy portion of D1A's range were located in traditional positions for historical troops D and E. Both troops ate significantly more mature leaves from the tamarind trees in the closed canopy forest, where the leaves had significantly higher nutritional content (water and protein) than that of open forest samples. They fed on tamarind fruit significantly more often in the open forest away from the river, where it was more abundant. The lemurs selected a diet that maximized leaf water and protein and ranged where fruit was most abundant but at high energetic costs for troop D1A.