3.1 Individual vigilance
In total, we obtained 870 mins observations from 34 family groups. For each family the observation lasted for 10.2 mins on average (range: 2.2-23.5 mins), which met our expectation of 10 min.
Adults spent significantly more time on vigilance (adults: 27.30-31.28%vs juvenile: 8.74-16.65%; p <0.05) and relatively longer vigilant bout (adults: 17.4-12.8s vs juvenile: 8.4-11.8s; p >0.05) than juveniles (Table 1). No significant difference in adult vigilance proportion (F =0.106,df =2, p =0.899) and duration (F =0.833, df =2,p =0.440) among three family groups existed.
Vigilance behavior of adults was closely related to observer distance (vigilance proportion: F =3.139, df =24, p =0.001; vigilance duration: F =1.804, df =24, p =0.053) while juvenile vigilance was not significantly correlated with any of the variables of family type, disturbance level and observer distance (p <0.05, Appendix table 1).
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