And the answer: dolphin.
Dolphins and whales typically give birth tail-first in order to prevent their calves from drowning during the birthing process. This usually takes a couple of hours, and the baby will be ready to swim by the time it leaves the womb.
While nine months certainly feels like a long time to carry a child, some marine mammals endure pregnancies that can span almost double that time. For the average bottlenose dolphin, a nine month period is all that it takes to carry their calf to term, but for other dolphin species, gestation can take anywhere from 10 to 16 months. What’s more: in order to guide their calves to air, dolphins will endure several hours of birth (tail-first, no less) before severing the umbilical cord and teaching their offspring to swim.
Luckily, dolphins make for excellent mothers. Studies show that adult dolphins will vigilantly guide their calves for at least the first five years of their life— teaching them social skills, hunting strategies, navigation, and more. Most dolphins nourish their calves with milk for the first two to three years of their life, but some have been documented nursing their offspring for up to ten years after birth!
In the first few moments of a dolphin’s life, its mother will usher it to the surface for its first breath of fresh air. However, it takes some time for the newly born calf to get adjusted to its new environment, and the baby dolphin will begin to breathe by “chin slapping,” or raising its head higher than necessary to ease into the breathing process. Soon, the calf learns to swim around his mother for both nursing and “slip-streaming,” which refers to a low pressure area created around the mother dolphin while she swims. This strategy enables the calf to save its energy, and allows it to begin its period of rapid growth.
Learn more about dolphin gestation and motherhood here.