Cetartiodactyls are monogamous, polyandrous, polygynandrous, or polygynous. Polygyny, in which social groupings consist of adult females and their young and one or a few adult males, is a common cetartiodactyl strategy. It occurs in species as different as elk (Cervus elaphus) and killer whales (Orcinus orca). Sexual dimorphism in ornamentation (such as antlers) and body size indicates intense male-male competition for mates in many species.
Mating System: monogamous ; polyandrous ; polygynous ; polygynandrous (promiscuous)
In general, cetartiodactyls are not highly prolific, giving birth to just one or two young every one or two years. However, some members of the family Suidae may have 12 or more young at a time. Breeding may be either seasonal or year-round. At least one species, the minke whale (Balaenoptera acutorostrata) regularly experiences a postpartum estrus. Gestation periods are as short as four months in small artiodactyls to as long as 17 months in Baird's beaked whales (Berardius bairdii), and youngsters are weaned between 2 1/2 and 24 months of age. Age at sexual maturity varies widely as well, from 5 months to more than 10 years.
Key Reproductive Features: iteroparous ; seasonal breeding ; year-round breeding ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); viviparous ; post-partum estrous
Most cetartiodactyls have precocial young, as it is necessary for them to be able to walk or swim from the moment of birth. Young stay with their mothers for at least four months. In some species, such as bottlenosed dolphins (Tursiops truncatus), young remain with their mothers for up to five years, long after they are weaned. Males may care for their offspring indirectly by defending family groups, but they generally do not help females raise their young.
Parental Investment: precocial ; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female); pre-weaning/fledging (Provisioning: Female, Protecting: Male, Female); pre-independence (Provisioning: Female, Protecting: Male, Female); post-independence association with parents; extended period of juvenile learning; maternal position in the dominance hierarchy affects status of young