Watering holes are often exciting places to watch animals interact, and new video from Kruger National Park in South Africa doesn't disappoint.

While touring the massive park, a couple happened upon a wildebeest that had just been bitten by a crocodile. It's likely the herbivore had approached the water for a drink when it was ambushed from below. The wildebeest struggled to free itself but the crocodile kept a firm grip on the slender leg in its powerful jaws.

For nearly eight minutes, the wildebeest and crocodile were engaged in a ferocious game of tug-of-war, and eventually the wildebeest appeared to tire.

Slowly the crocodile began to drag the wildebeest under water. Crocodiles, with their long, heavy bodies and stubby legs, have the biggest advantage over large prey like wildebeest when submerged.

As the wildebeest becomes more and more overwhelmed by the water and the crocodile's persistent pull, two hippopotamuses approach from offscreen. Suddenly, they charge toward the crocodile, causing it to lose its grip on the wildebeest. The mammal broke free. But with a likely broken leg, it may not survive long.

So did the hippos rush in to "save" a wildebeest in need?

Not likely, says Douglas McCauley, a National Geographic explorer and professor at the University of California Santa Barbara. Despite the fact that they're herbivores too, hippos can be extremely aggressive. Earlier this month, a sleeping hippo in Kenya was startled by a lion and snapped the big cat's neck.

McCauley offered two theories for why the hippos, likely sub-dominant males, incidentally "freed" the wildebeest.

The first is that the crocodile had encroached too closely on the hippos' territory. Hippos and crocodiles, which both frequent watering holes, generally are wary of each other. Hippos are too big and powerful for crocodiles to eat and hippos generally confine their prey to vegetation. But when a crocodile gets within about two meters (six feet) of a hippo, the territorial mammals may snap or charge, says McCauley.

McCauley's second hypothesis, the one he says is more likely in this case, is that the wildebeest's splashing prompted the hippos to stake their territory.

"My best guess is that the hippos are acting very aggressive toward anything that tries to enter the water. They'll come charging in and try to drive you away," he explained. (Watch what happens when a hippo attacks a boat.)

In other words, while the hippos appear to be "rescuing" the wildebeest in the video, it's more likely they were aggressively claiming their territory.