Wild baboons accustomed to human observers still do not consider them a neutral presence, according to a new study.
It provides the first empirical evidence, the researchers say, that tolerance towards human observers is a personality trait that varies from one individual animal to the next, not a quality that applies equally to all members of a group.
Andrew Allan from the University of Durham, UK, who led the study, says behavioural ecologists have tended to assume that habituated animals simply ignore people, but there is a lack of empirical evidence to support this.
To test it, he, Annie Baily and Russell Hill – who all are involved with Primate and Predator Project at the Lajuma Research Centre in the western Soutpansberg Mountains of South Africa – documented their tailored interactions with 69 chacma baboons (Papio ursinus) at the centre.
Each was approached repeatedly by two observers – one familiar and one unfamiliar – who walked directly towards them without pausing, dropping markers on the ground to measure the distance at which the baboon turned to look at them (visual orientation distance) and the distance at which it moved away (flight initiation distance).
They completed 1656 trials in total, finding that the identity and personality of the individual baboon played the greatest role in predicting which response would occur.
“Observers do not appear to be considered equivalent to a predator. Instead, baboon responses mimic typical responses to approaches from dominant or threatening conspecifics,” they write in a paper in the journal Science Advances.
“This suggests that observers are unlikely to be considered ‘neutral’ but are instead more equivalent to a high-ranking social threat.”
The researchers acknowledge that the way they approached the baboons was atypical, but suggest the findings point to the need to further investigate whether wild animals are impacted by human observers, which could lead to biased research results.
“Much animal behaviour research uses direct observations on habituated subjects, and we need to consider the extent to which our presence may influence the data we collect,” says Allan.