Breeding Seasonality in Female Vervet Monkeys (Chlorocebus pygerythrus) Living in an Anthropogenic Landscape

Resource availability is intricately linked to female reproductive success, and poor timing of reproduction can negatively impact maternal and/or infant survival. Thus, females should exhibit flexibility in the timing of reproduction that reflects local conditions. We examined eight years of data on births, conceptions, mating seasonality, and interbirth intervals (IBIs) in relation to food availability, weather, and female dominance rank in three groups of vervets (Chlorocebus pygerythrus) living in a forest-agriculture matrix near Lake Nabugabo, Uganda. Births (N = 126) occurred year-round but were moderately seasonal (61.1% of births in October-December). The degree of seasonality varied slightly between groups. However, there was no survival difference for infants born within or outside of birth peaks. Fruit availability did not vary seasonally, nor did feeding on either natural or anthropogenic foods. IBI did not vary between groups but was shorter than those of other wild populations, with most females breeding in successive years. Higher-ranking females had shorter IBIs than lower-ranking females. The moderate breeding seasonality and shorter IBIs in the Nabugabo vervets compared with other populations may relate to habitat differences and latitudinally-variable factors. The maintenance of a birth peak despite consistent food availability suggests vervets and other primates may be phylogenetically constrained, which prohibits adapting to changing environmental conditions, such as climate change.