We are all used to seeing acrobatic dolphins surfing and jumping effortlessly through the ocean. But until recently, we were unaware of the expectant mothers lagging behind their pod.
Dr. Shawn Noren and her team observed dolphins (located in Hawaii) for 10 days before giving birth and followed their progress for 2 years after calving. Dr. Noren observed that during their 12-month gestation period, dolphins develop a ‘bump’ akin to the ‘bumps’ seen in humans. However, for a marine mammal designed to be streamlined, the ‘bump’ could drastically affect an expectant mother’s lifestyle and lifespan!
Dr. Noren explained how the drag experienced by an expectant mother effects their speed:
“When a pregnant animal is swimming at 1.7 metres per second, it has the same drag force acting on it as a non-pregnant dolphin swimming at 3.4 metres per second.”
“So the pregnant dolphin can only go half the speed as the non-pregnant dolphin before it gets the same drag force.”
Dr. Noren also observed the arc of the tail whilst swimming reduces by 13% in a pregnant female. This is thought to be down to the location of the foetus in the abdomen creating surface tension in the mother’s skin, reducing its flexibility.
These two factors slow pregnant females to a maximum speed of 13km/h (8mph), which is markedly slower than a non – pregnant female whom can reach speeds in excess of 22km/h (14mph). This puts them in danger of becoming ‘easy prey,’ as the top speed of their natural predators would be equal to, or higher than, the maximum speed of a pregnant dolphin.
Pregnant humans may feel ‘less streamlined’ as the weeks pass by, but at least they are not reliant on their shape to glide through the world’s oceans like these graceful mammals!
By Haley Dolton
