Seasonal dietary variation and its implications for primate extinction risk

Previous research has shown that ecological specialization is a key biological predictor of extinction risk. Ecologically specialized taxa are less able to adapt and survive under various environmental scenarios. Ecological specialization may be measured along several niche axes, with dietary niche being a common focus of analysis. Several measures have been used to quantify dietary specialization including, the number of food species eaten and the ability to consume different types of food (e.g fruit, leaves, animal matter). These measures do not account for seasonal shifts in diet, which may be especially important during time of low food availability. The goal of this current study was to quantitatively investigate the role of seasonal changes in diet and its ability to predict species’ extinction risk. Data for over 30 primate species were gathered from the literature. Dietary seasonality was defined as the coefficient of variation in the monthly leaf and fruit consumption of each species. In addition, several other well-established predictors of extinction risk were included as independent variables. These predictor variables were used in multivariate generalized linear regressions to predict species’ IUCN category. Several independent variables were statistically significant predictors of extinction risk, including the degree of seasonal variation in fruit consumption. Species that exhibited more across-month variation in fruit intake displayed a lower risk of extinction. These results show that the ability to switch resources during times of low preferred food availability may increase species’ survival.