Evaluate the collective function of references cited together in a given text segment.
Classify their combined role into one of the following categories: 'method', 'background', or 'result'.

Text:Among these traits are strict seasonal breeding, cathemerality (equal activity during both day and night), low basal metabolic rates, a low degree of frugivory (a highly variable food source) for primates of their body size, female dominance, and a lack of sexual dimorphism (reviewed in Wright 1999). Given the costs of pregnancy and lactation in lemurs, females of many lemur species are 16 Anim Cogn (2012) 15:15–25
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