BOTTLENOSE DOLPHINS - Reproduction. Birth and care of young
Age when attaining sexual maturity is variable among bootlenose dolphins. On average , females become sexualy mature at about 5 to 12 years. Males become sexually mature at about 10 to 12 years. Females seem to be sexually receptive during a large part of the year and are generally responsible for initiating courtship and breeding behavior.Bottlenose dolphins may breed throughout the year. However, certain breeding seasons have been observed and vary with location. Breeding seasons generally coincide with calving seasons. Worldwide, calves are born throughout the year. Seasonal calving peaks vary by area.Peak calving appears to be bimodal for dolphins in Florida's Indian River Lagoon; most births occur in April and August. A female dolphin caon potentially bear a calf every two years, but calving intervals generally averabe three years.
Calves are born in the water. Sometimes an assisting dolphin may stay close to the new mother and calf. Althought this assisting dolphin often is referred to as an "aunte: dolphin, it may be male or female. This "auntie" dolphin is often the only other dolphin a mother allows near her calf.In the first few days after birth , the dorsal fin and tail flukes are flaccid and pliable, but gradually become more stiff. Calves are darker than adults and show several vertical, light-colored lines on their sides, a result of fetal folding. These lines disappear within six months. Calves nurse under water, lose to the surface. Observations in zoological parks show that nursing usually begins within six hours of birth. A calf nurses as often as four times per hour for the first four to eight days. A mother dolphin stays close to her calf and attentively directs its movements.
The baby swims close to its mother and is carried in the mother's "slip stream", the hydrodynamic wake that develops as the mother swims. This helps the baby to swim and enables the mother and calf to stay with up with the group. Bottlenose dolphins breeding colonies in marine zoological parks continue to provide a unique opportunity to observe and quantify aspects of dolphin biology. In zoological environments, calves begin to take a few fish at about three to four months, when their teeth begin to erupt. Within a few days of birth a calf can vocalize, but signature characteristics develop with age.