Answer: Giraffes

Giraffes have the highest known blood pressure of any creature on earth for a very good reason: their hearts are fighting gravity every step of the way. Just like we use pumps to transport water up to the top of lofty water towers, giraffes require a strong heart and high blood pressure to push blood all the way up the lengthy neck that is a significant part of their 14.1–18.7 feet high bodies.

How high is their blood pressure? While a human being in good health and with average blood pressure has a blood pressure of around 120/80 mm Hg, giraffes maintain blood pressures that are at least approximately twice that of humans and it can skyrocket much higher when the animal is running or otherwise exerting itself.

Don’t worry though, giraffes have evolved to sustain the significantly higher blood pressure. Not only are the walls of their hearts incredibly thick and muscular (much like we design the walls of a boiler to withstand higher pressure), but giraffes have a mechanism for selectively expanding and contracting blood vessels to control and route blood through their body to regulate local pressure.