Testing central place foraging in eastern chipmunks, Tamias striatus, by altering loading functions

Sleeping sites provide new insight into multiple central place foraging strategies of Tibetan macaques (Macaca thibetana)

Food resources, including food types, quantity, and quality, are the key factors that determine the survival and reproduction of wild animals. However, the most basic requirement is access to food. The choice of sleeping sites plays a crucial role in efficiently acquiring food and provides a useful starting point for studying foraging strategies. We collected data on sleeping site and foraging patch uses of wild Tibetan macaques (Macaca thibetana) in Huangshan, Anhui, China, from September 2020 to August 2021. We found that Tibetan macaques used 50 different sleeping sites, mostly located on cliffs, some of which they reused. Sleeping site altitude differed significantly according to season, with higher altitudes recorded in summer and winter. Tibetan macaques did not sleep as much as expected in the peripheral regions of their home range. The sleeping sites were often distributed in proximity to foraging patches, and there was a positive correlation between the use of sleeping sites and surrounding foraging patches. The utilization of foraging patches by Tibetan macaques is inclined towards the multiple central place foraging strategy. Our results provide supportive evidence for the proximity to food resource hypothesis and indicate the important role of sleeping sites in food resource utilization in Tibetan macaques.

A Breath of Fresh Air in Foraging Theory: The Importance of Wind for Food Size Selection in a Central-Place Forager

Empirical data about food size carried by central-place foragers do not often fit with the optimum predicted by classical foraging theory. Traditionally, biotic constraints such as predation risk and competition have been proposed to explain this inconsistency, leaving aside the possible role of abiotic factors. Here we documented how wind affects the load size of a central-place forager (leaf-cutting ants) through a mathematical model including the whole foraging process. The model showed that as wind speed at ground level increased from 0 to 2 km/h, load size decreased from 91 to 30 mm², a prediction that agreed with empirical data from windy zones, highlighting the relevance of considering abiotic factors to predict foraging behavior. Furthermore, wind reduced the range of load sizes that workers should select to maintain a similar rate of food intake and decreased the foraging rate by ∼70% when wind speed increased 1 km/h. These results suggest that wind could reduce the fitness of colonies and limit the geographic distribution of leaf-cutting ants. The developed model offers a complementary explanation for why load size in central-place foragers may not fit theoretical predictions and could serve as a basis to study the effects of other abiotic factors that influence foraging.