Ecosystem services expand the biodiversity conservation toolbox – A response to Deliège and Neuteleers

Wildlife tourism is proliferating worldwide and has the potential to raise revenue for conservation as well as public awareness of conservation issues. However, concerns are growing about the potentially negative influence of such tourism on the wildlife involved. We investigate the effects of habituation, ecotourism and research activities on levels of faecal glucocorticoid metabolites (FGCMs), a proxy for physiological stress, in wild western lowland gorillas (Gorilla gorilla gorilla) in the Central African Republic. We compare FGCMs in three human-contacted groups with those in unhabituated gorillas. We also explore how human–gorilla contact influences FGCMs of a gorilla group undergoing habituation and investigate how measures of general human–gorilla contact, tourism and human proximity influence FGCMs in recently and long-term habituated groups. Two of the three human-contacted groups had higher levels of FGCMs than unhabituated gorillas. The group undergoing habituation had the highest FGCMs, which increased up to 21 days following contacts, suggesting a cumulative FGCM response, in line with descriptions of a hormonal adaptation response to a chronic intermittent stressor. FGCMs in habituated groups were significantly associated with increasing frequency of violation of the 7 m distance rule by observers and with a medical intervention but not with other measures of human pressure. Our findings provide critical information for the management of this, and other, species whose conservation depends on habituation for ecotourism.