Some of the best evidence of the effects of resource competition

Some of the best evidence of the effects of resource competition on females comes from studies of the effects of increasing group size, which commonly depress fecundity and increase mortality of females and their offspring (Clutton-Brock, Albon & Guinness, 1982, van Schaik et al., 1983; Clutton-Brock, 2009b, 2009b, Silk, 2007a; Clutton-Brock, Hodge & Flower, 2008). Very similar patterns of resource competition occur in males, where breeding activity can also have high energetic

costs (Lane et al., 2010), and individuals compete both for direct access to resources Sunitinib and for access to feeding territories (Clutton-Brock, 2007), and survival is often sensitive to food shortages (Clutton-Brock, Major & Guinness, 1985). As well as competing for access to resources, females, like males, often compete to breed and, as in males, the structure of social groups intensifies conflicts of interest between group members (West-Eberhard, 1983, 1984). In some mammals, females compete to become sexually mature and, in extreme cases, one female suppresses the sexual development of all other females, evicting individuals that attempt BI 6727 clinical trial to breed (Creel & Creel, 2002; Clutton-Brock et al., 2006; Clutton-Brock, 2009b).

In others, females compete for access to mates, even though operational sex ratios (the ratio of males to females that are ready to mate at a given time) are biased towards males. For example, in some ungulates where males defend groups of females during a well-defined mating season, there is often more than one receptive female in a male’s harem on the same day, and females commonly compete for the attentions Progesterone of males (Bro-Jørgensen, 2002, 2011). Female competition may help females to ensure that they are mated by one or more males

within the time frame of their reproductive cycles (Parker & Ball, 2005), for the sperm supplies of successful males can become depleted (Dewsbury, 1982; Preston et al., 2001, Wedell, Gage & Parker 2002) or popular males may strategically conserve sperm for subsequent mating opportunities (Parker et al., 1996, Wedell et al., 2002). As would be expected, the frequency of overt female competition for mating partners increases in populations where adult sex ratios are strongly biased towards females (Milner-Gulland et al., 2003, Cheney, Silk & Seyfarth, 2012), where there is a high degree of reproductive synchrony (Emlen & Oring, 1977; Stockley & Bro-Jorgensen, 2011), or where females mate with multiple partners (Charlat et al., 2007).

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