Table 1 Factors hypothesized to influence VOD and FID in baboons.

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).

FactorsLink to sensory capacity/FID/personality
Response variable: VOD
Observer (pseudo-predator) identity, X1Unfamiliar 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, X7Local 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), X8Localized 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, X9When visual orientation interval (distance between VOD and FID) is long,
focal animals will flee sooner, resulting in longer FID.
Engaged/Not engaged, X10FID 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, X1Unfamiliar 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, X7Local 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.