Contextual variables that could be major drivers of VOD and FID responses in habituated chacma baboons (examples from relevant literature supporting the inclusion of each hypothesis can be found in table S1).
| Factors | Link to sensory capacity/FID/personality |
| Response variable: VOD | |
| Observer (pseudo-predator) identity, X1 | Unfamiliar observer considered a greater threat, leading to increased risk perception and tendency to visually orient, resulting in longer VOD |
| Trial number, X2 | (i) Increase or decrease in VOD with trial number indicative of habituation or sensitization (respectively) to FID approach methodology |
| (ii) Consistent individual VOD response through time indicates personality trait. | |
| Compatibility: Not engaged (looking/not looking), engaged (not looking), X3 | Looking may enable animals to collect multiple types of information concurrently; in addition, being “not engaged” may afford focal animals a greater sensory capacity for detection. As a result, individuals looking as approach commences will visually orient toward approaching observer sooner resulting in longer VOD; engaged should yield shorter VOD. |
| Habitat (open/closed), X4 | (i) “Open” habitats may afford individuals greater visibility, increasing likelihood of attending to approaching observer quicker, resulting in longer VOD. |
| (ii) Open habitats are generally considered safer for baboons, as they permit earlier detection and avoidance of predators; therefore, risk perception could be lower, reducing tendency to visually orient toward approaching observer, resulting in shorter VOD. | |
| (iii) Open habitats may increase risk perception, as focal animals are less concealed from potential threats, increasing tendency to visually orient toward approaching observer, resulting in longer VOD. | |
| (iv) Open habitats have lower refuge availability, which may increase risk perception, resulting in longer VOD. | |
| Height (ground/above ground), X5 | “Above ground” may afford individuals greater visibility, resulting in longer VOD. In this context, above ground is <50 cm from ground level and is unlikely to qualify as potential refuge and therefore should not influence risk perception. |
| Number of neighbors within 5 m, X6 | (i) As number of neighbors increase, the likelihood of a neighbor visually orienting toward the approacher increases, i.e., collective detection, which could result in longer VOD. |
| (ii) As number of neighbors increase, the likelihood of predation decreases reducing risk perception and the tendency to visually orient toward the approach observer, resulting in shorter VOD. | |
| (iii) Increasing number of neighbors may mask both the visual and audible cues associated with the observer’s approach, resulting in shorter VOD, e.g., neighbors draw visual attention away from observer or noises from neighbors mask the sounds of observer’s footsteps during approach. | |
| Neighbor flight, X7 | Local conspecifics initiating flight before the focal animal will increase risk perception and evoke vigilance. Both factors could lead to focal animals visually orienting toward approaching observer sooner, resulting in longer VOD. |
| External factors (local alarms, aggressions within 5 min), X8 | Localized threatening stimuli lead to increased risk perception and tendency to visually orient, resulting in longer VOD. |
| Localized visual and audible stimuli may reallocate some of the focal animal’s finite attention, resulting in longer VOD. | |
| Response variable: FID | |
| VODI, X9 | When visual orientation interval (distance between VOD and FID) is long, focal animals will flee sooner, resulting in longer FID. |
| Engaged/Not engaged, X10 | FID will be higher if focal animal was engaged at the start of the approach, as flight costs are higher because of interrupted social time (i.e., grooming) or loss of food patch (i.e., foraging). |
| Observer (pseudo-predator) identity, X1 | Unfamiliar observer is considered a greater threat; therefore, FID should be greater for unfamiliar observer |
| Trial number, X2 | (i) Increase or decrease in FID with trial number indicative of sensitization or habituation (respectively) to FID approach methodology |
| (ii) Consistent FID response through time indicates personality trait. | |
| Habitat (open/closed), X4 | (i) Open habitats are generally considered safer for baboons, as they permit earlier detection and avoidance of predators; therefore, risk perception could be lower, resulting in shorter FID. |
| (ii) Open habitats may increase risk perception, as focal animals are less concealed from potential threats, resulting in longer FID. | |
| (iii) Open habitats have lower refuge availability, which may increase risk perception, resulting in longer FID. | |
| Number of neighbors within 5 m, X6 | (i) Risk diluted with greater number of neighbors; therefore, FID should decrease as number of neighbors increases. |
| (ii) Increasing number of neighbors increases localized visual and audible stimuli and therefore may reallocate some of the focal animal’s finite attention resulting in decreased FID. | |
| Neighbor flight, X7 | Local conspecifics initiating flight before the focal animal will increase risk perception and therefore increase FID. |
| External factors (local alarms, aggressions within 5 min), X8 | (i) Localized threatening stimuli leads to increased risk perception and therefore increased FID. |
| (ii) Localized visual and audible stimuli may reallocate some of the focal animal’s finite attention therefore decreasing FID. | |