Dolphin Quest has announced two new arrivals both born on the same day.

The newborn calves arrived within 18 hours of each other on April 1, marking a double birthday for the marine park.

Caliban, a 17-year-old Atlantic bottlenose dolphin, gave birth at 12.28 a.m. Staff were just helping to settle the calf in when along came baby number two, born to 21-year-old Bailey at 6.03 p.m.

"Both Caliban and Bailey delivered their calves rostrum (head) first, which although not unheard of, is rare," said Roma Hayward, Marine Animals manager.

"The births went very smoothly, and mothers and calves appear healthy and active."

Dolphins have a year-long gestation period and the first few months of a calf's life are critical, as they learn to nurse and establish bonds with their mother.

Over the next several weeks Dolphin Quest's marine mammal specialists will be monitoring Caliban, Bailey and their calves on a 24-hour basis.

Another new arrival is also expected as Ely, Bailey's daughter, is due to give birth within the next few days.

All three dolphins were impregnated naturally by males Somers and Nimbus.

It is the fourth time Caliban and Bailey have given birth in Bermuda. The last new arrivals at the Dockyard Keep were in spring 2007 when they delivered calves within three days of each other.

Ely was born to Bailey on June 3 and Bermudiana to Caliban on June 6. Cirrus, a 33-year-old Atlantic bottlenose, also gave birth to Luna on May 23, 2007.

All three births were the result of artificial insemination using frozen semen brought to Bermuda from US marine parks part of a groundbreaking cetacean reproduction study in small population genetics.

Somers and Nimbus were recently moved to Dolphin Quest Hawaii.

The pair were originally proposed to be sent to the MGM Mirage Resort, Las Vegas, as part of a 'breeding loan'. Last month however, they were moved to a sister facility.

Christine Mihelcic, manager of Dolphin Quest Bermuda, said: "We were in talks with Las Vegas but decided to move them to our internal site on Hawaii's Big Island.

"We made the decision looking at all the variables and the bigger picture. It was nothing in particular, but that was the best move for us at that time, looking at population and diversity."

Dolphin Quest plans to run a baby-naming contest in May, once the sex of the dolphins are known. The birth of Ely's calf will bring the population at the Bermuda facility to 12, the maximum allowed by Government.