Filmmakers spent three years following and filming pandas in China’s Qinling Mountains.

Pandas (Ailuropoda melanoleuca) are popular for their comically round body shape and adorable antics, and videos of captive pandas playing in snow; rolling around like giant balls; using their heads to climb; or even accidentally face-planting, are undeniably enchanting. But when these bears are seen in their natural habitat, “there’s nothing cute and cuddly about them,” Jacky Poon, “Born to be Wild” filmmaker, said in the documentary. 

Adult male pandas can weigh as much as 300 lbs. (136 kilograms) and are nearly 7 feet (2 meters) tall when standing upright on their hind legs, according to the World Wildlife Fund. Pandas are highly territorial, and males usually interact with females only during mating season between March and May, WWF says.

Read our recent article: Are Giant Pandas still endangered in 2020?

In the tense standoff between the dominant, older male panda and an eager rival, the younger male eventually retreated, but when the female came down from her perch, she fought with the victor and escaped. For weeks, the two males trailed her, their growling challenges becoming more frequent and culminating in another tense confrontation. But a week later, when the female was finally ready to mate, just one suitor remained — the younger male. 

Male pandas’ bellowing, scent marking and female “hostage”-holding are mating behaviors that may trigger ovulation in female pandas. That could explain why pandas are so difficult to breed in captivity, in the absence of this male competition.