Adult male giraffes are much larger than females; they also carry a sizable head and neck. Like cats and dogs, giraffes do not experience estrous cycles, have breeding seasons, make mating calls, or show physical signs that they are ready to mate. So, how do giraffes mate?

The simple answer is: pee, pheromones and a gentle nudge, suggests a new study from the University of California, Davis. The study provides new insight into giraffes’ unique sex lives, their reproductive behaviors and how their anatomy supports those behaviors.

A male giraffe, called a bull, provokes the females to urinate by nudging them and sniffing their genitals. If the female giraffe-cow is interested, she widens her position and urinates for about 5 seconds.

The bull takes that urine in his mouth, curls his lip and inhales with his mouth open. This act, called flehmen, transports the female’s scent and pheromones from the oral cavity to the vomeronasal organ (VNO).

female giraffe drinks
A female giraffe drinks at a watering hole in Namibia while a male invites her to urinate, giving him clues to her sexual receptivity. (Lynette Hart, UC Davis)

Giraffes have papillae on their hard palates that each open into a nasopalatine tract that enters the vomeronasal organ (VNO), which is used for pheromone assessment. Unusually, giraffes were found not to have a prominent nasal connection to the VNO.

While several animals, such as cats and horses, exhibit flehmen, most mammals do not check their pee until it has touched the ground. However, the giraffe is not designed for such studies.

Lead author Lynette Hart, a UC Davis professor of public health and reproduction in the School of Veterinary Medicine, said: “They don’t risk going all the way to the ground due to the extreme development of their head and neck. So they have to nudge the female and basically say, “You have to pee now.” And often she will. He must elicit her cooperation. If not, he knows there is no future for him with her.”

Benjamin Hart, professor emeritus at the UC Davis School of Veterinary Medicine, said: “This is part of their reproductive behavior. This adds to our understanding of what giraffes do when they congregate around a water hole. People like to watch giraffes. I think the more the public understands about them, the more interested they are will be in its preservation.”

The Harts were able to get very close to dozens of giraffes gathered at waterholes in Namibia’s Etosha National Park.

Magazine reference:

  1. Lynette A. Hart, Benjamin L. Hart. Flehmen, osteophagy and other behaviors of giraffes (Giraffa giraffa angolensis): Vomeronasal organ adaptation. Animals. DOI: 10.3390/ani13030354