A comparison of postnatal arterial patterns in a growth series of giraffe (Artiodactyla:Giraffa camelopardalis)

A newborn giraffe already has an adult-style blood supply to its brain. In many mammals, a major artery carries blood directly towards the brain. Adult giraffes instead rely on a specialised arterial network, and the researchers wanted to know when that arrangement develops as a giraffe grows taller.

Haley O'Brien, Paul Gignac, Tobin Hieronymus and Lawrence Witmer studied three female giraffes that had died in managed care: a stillborn calf, a six-month-old juvenile and an elderly adult. They filled blood vessels with material visible on CT scans and reconstructed the arteries in three dimensions. This let them compare the routes supplying the brain, face and developing horns without relying only on dissection.

Even the newborn had a well-developed arterial network and no open proximal internal carotid artery, indicating that this vessel had closed before birth. Most arteries supplying the brain and skull base followed the same pattern across all three ages. The blood supply around the horns changed more clearly as those structures developed. Three specimens cannot capture all individual variation, and the scans show anatomy rather than blood flow in living animals. Still, the comparison places a major feature of adult giraffe circulation before the calf ever begins its rapid postnatal growth.