Table 2. Literature examples for assessing predictions concerning vigilance responses. Predictions were: more time is spent vigilant or less time is spent foraging or resting when disturbance stimuli (A) approach more directly, (B) remain at closer distances, (C) have a greater group size (e.g., more ecotourists), and (D) occur concurrently with a greater level of natural predation risk (see the Vigilance section for details).

Study Species Stimuli Predictions       Supported Rejected Not tested or controls lacking Burger and Gochfeld (1998) several waterbird spp. people on foot C A, B, D   Duchesne et al. (2000) woodland caribou people on skis or snow shoes C A, B, D   Frid (2001b) Dall’s sheep fixed-wing aircraft A B, C, D   Galicia and Baldassarre (1997) American Flamingo motorboat C B A, D   Papouchis et al. (2001) bighorn sheep cars, bikes C A, B, D   Stockwell et al. (1991) bighorn sheep helicopter A B, C, D   Ward and Low (1997) American Crow urban pedestrians and traffic B, D A, C