Sensory information and associative cues used in food detection by wild vervet monkeys

Abstract

Understanding animals' spatial perception is a critical step toward discerning their cognitive processes. The spatial sense is multimodal and based on both the external world and mental representations of that world. Navigation in each species depends upon its evolutionary history, physiology, and ecological niche. We carried out foraging experiments on wild vervet monkeys (Chlorocebus pygerythrus) at Lake Nabugabo, Uganda, to determine the types of cues used to detect food and whether associative cues could be used to find hidden food. Our first and second set of experiments differentiated between vervets' use of global spatial cues (including the arrangement of feeding platforms within the surrounding vegetation) and/ or local layout cues (the position of platforms relative to one another), relative to the use of goal-object cues on each platform. Our third experiment provided an associative cue to the presence of food with global spatial, local layout, and goal-object cues disguised. Vervets located food above chance levels when goal-object cues and associative cues were present, and visual signals were the predominant goal-object cues that they attended to. With similar sample sizes and methods as previous studies on New World monkeys, vervets were not able to locate food using only global spatial cues and local layout cues, unlike all five species of platyrrhines thus far tested. Relative to these platyrrhines, the spatial location of food may need to stay the same for a longer time period before vervets encode this information, and goal-object cues may be more salient for them in small-scale space.

Partially shared consensus decision making and distributed leadership in vervet monkeys: older females lead the group to forage

“…Thus, the motivation for these males to leave the sleeping site appeared to be gaining access to a feeding area with easy to acquire, calorific human food before other group members. The same pattern was noted during feeding experiments on this same group of vervets (Teichroeb & Chapman, ). When experiments were set up and baited near the sleeping site, adult and subadult males left the sleeping trees at first light to gain access to the rewards available at experimental sites before others in the group could approach.…”

Playing it safe? Solitary vervet monkeys (Chlorocebus pygerythrus) choose high‐quality foods more than those in competition

“…Visual cues in foraging may be even more important in catarrhine primates who possess enhanced visual abilities (e.g., trichromacy) relative to other sensory capabilities such as olfaction (Teichroeb & Kumpan, ). Indeed, previous foraging experiments have shown that vervets predominantly rely on visual signals to locate food rewards (Teichroeb & Chapman, ). It is thus possible that the differences in quantity in Teichroeb and Aguado () were easier for the monkeys to differentiate based on visual cues than the differences in quality in this study, which did not impart any unique visual signals (each piece of popcorn looked the same regardless of nutritive quality).…”

“…This was important to assess because in the remaining phases, we manipulated the nutritional composition of the popcorn on the platforms and indicated which platform(s) had nutritionally different rewards to the monkeys using the flagging tape beacon. Vervets have a trichromatic color vision (Jacobs, ) and we knew from a previous experiment that vervets easily learned to associate a beacon with a reward (Teichroeb & Chapman, ). The flagging tape beacon was found to work well because it was visible from a long distance and the monkeys did not have to see the top of the platform to see the beacon.…”

Social Behaviours and Networks of Vervet Monkeys Are Influenced by Gastrointestinal Parasites

“…In this study, oral ivermectin was placed within a banana slice and given to specific individuals when they were foraging in isolation. This method of baiting had been well tested on the study group [44]. At this time, direct faecal smears of adults and subadults were carried out daily, with samples collected opportunistically.…”