EFFECTS OF GROUP SIZE AND SEX ON VIGILANCE IN OSTRICHES ( STRUTHIO CAMELUS ): ANTIPREDATOR STRATEGY OR MATE COMPETITION?
1988; Taylor & Francis; Volume: 59; Issue: 1 Linguagem: Inglês
10.1080/00306525.1988.9633919
ISSN1727-947X
AutoresJoanna Burger, Michael Gochfeld,
Tópico(s)Avian ecology and behavior
ResumoSummary Burger, J. & Gochfeld, M. 1988. Effects of group size and sex on vigilance in Ostriches (Struthio camelus): Antipredator Strategy or Mate Competition? Ostrich 59:14-20. We studied vigilance behaviour in wild Ostriches (Struthio camelus) in five game parks in Kenya. In 173 groups ranging from one to ten ([xbar] = 2,8 ± 2,5) birds, the overall sex ratio was 1 male: 0,78 females. Using focal animal sampling and one minute time blocks, we recorded time spent feeding, head up, walking, and preening. Data were analyzed using multivariate regression models. The variance in vigilance behaviour and time devoted to eating was explained by sex, flock size, distance from observer to the flock, nearest neighbour distance and park (but not vegetation cover). We suggest that vigilance in females relates primarily to predation pressure, and thus decreases with group size. However, in males vigilance relates to both predation pressure and social factors (male-male competition). These results suggest that vigilance behaviour does not respond to only one selective force, but must be examined in light of conflicting selection pressures.
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