Little information is available regarding the mating systems of rough-toothed dolphins in the wild.
The reproductive habits of rough-toothed dolphins are not well known, though captive studies provide some information. At birth, rough-toothed dolphins measure 1 to 1.3 m in length. Calves attempt to nurse within an hour of birth, but are initially unsuccessful, unable to connect to their mother’s mammary slits. Within the first 3 days, calves can successfully nurse, which takes place underwater and occurs throughout the day. Calves nurse, rest, and play on a daily basis. Play time generally follows nursing and includes exploration to the surface while staying in close proximity to the mother. Calves rest around midday for about 60 minutes. At 2 months of age, calves begin to eat fish and decrease nursing time.
Rough-toothed dolphins exhibit sexual dimorphism, and mature males are longer than mature females. In both sexes, the most rapid growth occurs in the first 5 years. Females reach sexual maturity at 9 to 10 years of age at a length of 212 to 217 cm and a weight of 101 to 108 kg. Males reach sexual maturity at 5 to 10 years of age at a length of about 216 cm and a weight of 92 to 102 kg.
Range weaning age: 2 (low) months.
Range age at sexual or reproductive maturity (female): 9 to 10 years.
Range age at sexual or reproductive maturity (male): 5 to 10 years.
Key Reproductive Features: gonochoric/gonochoristic/dioecious (sexes separate); sexual ; viviparous
In captivity, female rough-toothed dolphins protect their calves by swimming in close proximity to their young and positioning themselves between the calf and other dolphins. The length of the mother-calf relationship is unknown. A female rough-toothed dolphin, presumed to be the mother, was observed supporting a dead calf at water's surface for several days. During this time, she was escorted and protected by a number of male rough-toothed dolphins. This may demonstrate a prolonged mother-calf association in rough-toothed dolphins. Such behavior has been observed in the tight social groups of other marine mammals.
Parental Investment: precocial ; female parental care ; pre-hatching/birth (Provisioning: Female); pre-weaning/fledging (Provisioning: Female); pre-independence (Provisioning: Female)