Sexual Dimorphism and Social Structure
Modern felids demonstrate excellent examples of sexual dimorphism as a function of competition between males for females. Lions, for example, have a high degree of competition for females. Because a single male controls of a pride of many females, the male has been selected for size and power. Tigers, in contrast, exhibit only a small amount of sexual dimorphism because single individuals tend to control their own territories. Distinct males rarely come into contact with one another and substantial sexual dimorphism has not been selected for.
Smilodon exhibits only a small amount of dimorphism. There is very little overall size dimorphism, and only a slight dimorphism in the enlarged canines. Thus, it is believed that Smilodon shared a similar lifestyle and social structure to modern tigers, where males faced little competition for females and generally pursued only one at a time. This also suggests that Smilodon did not live in groups and was solitary like modern tigers (Valkenburgh & Sacco, 2002).