Most studies on spatial memory in primates focus on species that exploit the flesh of ripe fruits, which is the patchiest resource available to animals inhabiting tropical forests. Futhermore, these studies usually focus on primates exploiting very large home ranges. Behavioral adaptations associated with enhanced spatial memory, distance-minimization, and fine-tuned food search methods are expected to be at a premium for animals that cover a lot of ground each day exploiting clumped and ephemeral ripe fruits. The purpose of the current study is to gain insights into the foraging strategy of a seed predator exploiting a relatively small home range. While still a patchy resource, seeds are more abundant in space and time than fleshy ripe fruits. Additionally, it is assumed that animals with small home ranges can more readily encounter resources in their supplying area without having to rely upon sophisticated foraging strategies.
I investigated the modes and efficiency of travel in a group of white-faced sakis in Brownsberg Nature Park, Suriname. Using detailed maps of their daily movements, I determined that the sakis travel more quickly and more linearly to a restricted subset of food resources. Furthermore, they were able to arrive at reused feeding sites using alternate and direct pathways. Both of these behaviors are consistent with the use of spatial memory to locate resources, and, more importantly, goal-directed foraging behavior, a search technique primarily associated with ripe fruit eaters inhabiting large home ranges.
While the sakis’ paths were slightly less linear than expected, linearity scores mirrored observations of goal-directed white-faced sakis studied in Venezuela. A number of behaviors and scenarios appear to lower their ability to maintain perfectly linear paths, including, their tendency to monitor the curved perimeter of their territory, their frequent participation in territorial encounters with conspecifics, their zig-zagged movements when sampling resources, and their reliance on and propensity to diverge off of established arboreal pathways to home in on particular sites. They use a small number of arboreal pathways to negotiate the numerous gaps in the canopy throughout their range and to bring them into contact with important feeding areas, overlap zones, and particular trees; however, it appears that they do have the ability to navigate solely by orienting towards certain landmarks in their range.