Mammal: Difference between revisions

On average, [[male]] mammals are larger than females, with males being at least 10% larger than females in over 45% of investigated species. Most mammalian orders also exhibit male-biased [[sexual dimorphism]], although some orders do not show any bias or are significantly female-biased ([[Lagomorpha]]). Sexual size dimorphism increases with body size across mammals ([[Rensch's rule]]), suggesting that there are parallel selection pressures on both male and female size. Male-biased dimorphism [[Sexual selection in mammals|relates to sexual selection]] on males through male–male competition for females, as there is a positive correlation between the degree of sexual selection, as indicated by [[mating system]]s, and the degree of male-biased size dimorphism. The degree of sexual selection is also positively correlated with male and female size across mammals. Further, parallel selection pressure on female mass is identified in that age at weaning is significantly higher in more [[Polygyny in animals|polygynous]] species, even when correcting for body mass. Also, the reproductive rate is lower for larger females, indicating that fecundity selection selects for smaller females in mammals. Although these patterns hold across mammals as a whole, there is considerable variation across orders.<ref>{{cite book | vauthors = Lindenfors P, Gittleman JL, Jones KE |title= Sex, Size and Gender Roles: Evolutionary Studies of Sexual Size Dimorphism |chapter= Sexual size dimorphism in mammals |date=2007 |publisher=Oxford University Press |location=Oxford |isbn=978-0-19-920878-4 | pages = 16–26 |url=https://swepub.kb.se/bib/swepub:oai:DiVA.org:su-16290?tab2=abs&language=en}}</ref>