Resource Tracking: Food Availability and Propithecus Seasonal Reproduction

Abstract

In order to examine the ultimate causes of the strict reproductive seasonality found among Malagasy primates, we compared the feeding ecology and reproductive timing of two Propithecus species in dry forest and in rain forest. We examined the associations between phenology, feeding behavior, and foraging effort over an annual cycle in golden-crowned sifaka (P. tattersalli) and Milne-Edward’s sifaka (P. diadema edwardsi). Specifically, we described resource tracking and reproductive timing for P. tattersalli in very seasonal northern forests and then examined whether P. diadema edwardsi in the less seasonal southeastern rain forest follows similar patterns. Propithecus tattersalli tracks immature leaves such that when they are available this sifaka will concentrate on this food type regardless of the high availability of staple foods such as seeds and mature leaves. Correlation matrices were used to examine the relationships among food availability, diet and foraging effort. Immature leaf consumption was correlated positively with both immature leaf availability and with DPL in the golden-crowned sifaka. The strongest positive correlation was immature leaf availability with DPL and the strongest negative correlation was mature leaf feeding with DPL. High immature leaf availability and high levels of immature leaf feeding occurred in the early wet season. Propithecus diadema edwardsi also increased immature leaf feeding frequency and as well increased total feeding time during periods of increased immature leaf availability. The timing of high immature leaf feeding and availability was similar at both sites. In both species, infants were born in June or July and were weaned in November and December. As Propithecus species are anatomical folivores, the increased nutrient demands on lactating females may require higher quality foods as well as higher levels of food intake. In both species, the period of highest immature leaf intake was during late lactation and weaning. Slight differences in the two species’ responses to seasonality suggest that, although reproduction may be timed such that late lactation and weaning coincide with high levels of immature leaf availability, resource seasonality alone may not be the ultimate cause of strict breeding seasonality in sifaka.