Sexual dimorphism in pinnipeds particularly elephant seals is the most pronounced among Carnivorans.Sexual dimorphism in lions is the most prominent among felids
Sexual dimorphism is the condition where sexes of the same species exhibit different morphological characteristics, particularly characteristics not directly involved in reproduction.[1] Sexual dimorphism in carnivorans, in which males are larger than females, is common. Sexual selection is frequently cited as the cause of the intraspecific divergence in body proportions and craniomandibular morphology between the sexes within the Carnivora order.[2][3] It is anticipated that animals with polygynous mating systems and high levels of territoriality and solitary behavior will exhibit the highest levels of sexual size dimorphism. Pinnipeds offer an illustration for this.
Different types
Body size
Sexual size dimorphism is the difference in body size between the sexes within a group of some sort or another. Carnivorans exhibit high levels of sexual size dimorphism with males generally being larger than females.[4]
Canine tooth
Males have larger, longer and more powerful canines than their female counterparts. A study of skull and tooth size in 45 species of Carnivorans showed that sexual dimorphism was most pronounced in the size of the canine tooth.[2] Breeding systems seems to be the most reasonable explanation for the finding. Social species like lions, in which males have a canine teeth 25% larger than females are the most sexual dimorphic of felids.
Skeletal structure
In terms of skeletal structure,
Carnivorans are highly sexually dimorphic. Males have more robust and larger skulls which promotes a stronger biteforce, larger necks to permit more powerful neck muscles that work to prevent torsional loading of the neck and improve the ability to rend with the teeth and jerk the skull. Males also have larger scapulae that enable more muscle to transmit force from the trunk to the forelimbs and stabilize the shoulder joint and stronger limbs with better mechanical advantages due to anatomy.[5][6][7]
Mechanisms
A secondary factor that propels the evolution of sexual dimorphism might be provided by niche divergence and resource partitioning. For instance, the evidence for the divergence of the intersexual niche is found in the size and structure of the craniomandibular bones. The ecological difference between the sexes and even a decline in intersexual rivalry for resources and habitat usage is reflected in the skull's phenotypic variation.[8][9] It is well known that many carnivoran species' males and females use different dietary resources. This is frequently manifested in prey size, with males frequently consuming larger prey than their female counterparts.[10][11] Moreover, there is a correlation between sexual dimorphism and carnivory in carnivorans, meaning that species that are more carnivorous have larger size differences between males and females.[2][12] Hence, increased sexual dimorphism in obligate carnivores lessens intraspecific nutritional competition by minimizing conflict between males and females.[13]
Because they have an evolutionary impact on body size in both males and females, or both, sexual selection and natural selection are frequently seen as the main mechanisms behind sexual size dimorphism. It has long been assumed that sexual selection is the main cause of sexual size dimorphism in the majority of endothermic vertebrates (including mammals and birds), where the larger sex directly boosts its reproductive success through intrasexual competition.[14][15][16][17] The evolution of sexual size dimorphism has been theorized to be influenced or maintained by natural selection.[18] It is also possible that sexual selection has influenced the evolution of sexual size dimorphism, as suggested by the hyperallometric patterns found in both mammals and birds.
