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Group-living animals may need to spend less time being vigilant, consequently, having more time for other important activities such as foraging (i.e., group size effect). Przewalski’s gazelle (Procapra przewalskii) is a group-living social animal, and a study was conducted in Qinghai Province of China during June–August 2006 by using a continuous focal sampling method to investigate the influences of group size, sex, within-group spatial position, and nearest-neighbor distance on individual vigilance level (defined as scanning frequency per minute). Male gazelles were more vigilant than females. The gazelle’s vigilance level decreased with group size (group size effect), but only for females. The individuals at the central positions within a group were less vigilant than those at the peripheral positions, but the nearest-neighbor distance did not have any significant influence on the individual vigilance level. Our results support the hypotheses of group size effect and edge effects, but the sexual difference in vigilance level and in the response to group size effect on vigilance suggests that there may be sexual difference in the function and targets of vigilance behavior of Przewalski’s gazelles, which warrants more investigation, with incorporation of within-group spatial position, to better understand the mechanism underlying the group size effect and edge effect.
From August 1998 to August 2001, 119 wolf scats were collected from the desert in a pastoral region in northeastern Qinghai-Tibet Plateau, China. The study area is the last habitat for the critically endangered Przewalski's gazelle Procapra przewalskii. Wolf prédation was hypothesized as a cause of the endangerment of the Przewalski's gazelle. The diet of wolf during the plant green period (June-September) and the plant withering period (October-May) were determined using three scat-analysis methods: frequency of occurrence, mass in scats and the ingested biomass obtained with the linear regression models of Weaver (1993). Limited to mąmmalian prey, total agreement was found between thedry weight and biomass methods, but less so between the frequency of occurrence data and other methods. Hare, yak, and small rodents were the important prey species of the wolves during the plant green period, each accounting for 33, 27, and 20%. Yak, sheep and hare were the important prey species during the plant withering period, each accounting for 53, 25, and 17%. Other food types were badger, Przewalski's gazelle, birds, reptiles, invertebrates and plants. The presence of the livestock remains in the wolf's scats may imply scavenging behavior by the wolves, because few cases of missing livestock were reported during the study. No notable seasonal difference in the diet composition of the wolves was found. The food niche of wolf during the plant green period (0.55 ± 0.02) was similar to that during the plant withering period (0.50 ± 0.02).
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