Many animals, including Africa's Big Five, roam the savannas of the Sabi Sand Game Reserve in South Africa. Sometimes, these animals turn up in unexpected places – such as the young giraffe that game guides found up in a tree, hung over a fork, dead.
A large male leopard straddled the giraffe, its mouth blood-red. Apparently, the leopard had hoisted the giraffe several metres up the tree. The cat feasted for a few days, leaving only bones, skin and bits of flesh scattered around.
The giraffe weighed 300kg, about five times heavier than its killer. To match the leopard's feat of food-lifting, a man would have to heave almost 2000 Big Macs up two floors in one go.
It seems an utterly bizarre thing to do, but the leopard has a good reason for doing all this heavy lifting. If a leopard does not bother to hoist its kill into the tree, it risks losing its meal to hyenas and lions.
Keeping its kill in a tree helps a leopard to prevent theft, according to a study published in February 2017.
Leopards tend to hoist prey that are between half and one-and-a-half times their own weight
The study by Panthera – a non-profit organisation that focuses on wild cat conservation – found that leopards in the Sabi Sands Game Reserve hunt at least 40 species of prey, from fowls to young giraffes. Leopards hoist half of their kills, and hoisted kills were 67% less likely to be stolen. Still, leopards lose one out of five kills to other predators like spotted hyenas, lions and even other male leopards.
The game guides' familiarity with the leopards gave the scientists a "unique opportunity" to study the animals, says lead author Guy Balme. "The guides know the leopards as well as we know our neighbours." It also helps that "for the most part, leopards accept the game drive vehicles and just ignore them."
Balme and his team collated the guides' observations of leopards and their kills, which they record at the end of every day. Altogether, they analysed information on 104 leopards and 2,215 feeding events between 2013 and 2015.
The scientists found that leopards tend to hoist prey that are between half and one-and-a-half times their own weight. Kills too small or too large were often eaten on the ground. The likelihood of hoisting also spiked if hyenas or other male leopards show up.
If a leopard decides to hoist its prey and senses no competitor nearby, Balme says, it would drag it to find "a tree with a good fork or branch to drape the prey". This sometimes meant hauling it several hundred metres. Once there, the leopard leaps on to the trunk and hoists the prey up to 10m upwards. "These are very powerful cats. Incredibly impressive."
The study noted 39 cases of hyenas running off with food that leopards accidentally dropped from trees
However, the situation is sometimes more urgent. "If there's a hyena nearby, the leopard will immediately drag the prey and leap into the first tree it can find to keep the food safe," says Balme.
Spotted hyenas can hear the noises of a leopard kill, and they approach quickly. But hyenas do not just sit and wait for a kill. "Very often we see hyenas tracking leopards, because the chance of a free meal is high," says Balme. Hyenas commit half of all kill thefts from leopards. "They are a total nuisance for leopards in this area."
The hyenas are completely brazen about it. "They just ignore the leopard and go running in to grab the prey," says Balme. "We have seen only a handful of occasions where a large male leopard can fend off hyenas." On the ground, hyenas beat leopards most of the time, and sometimes even kill the cat.
Fortunately for leopards, hyenas cannot climb trees. That means leopards can guzzle in a tree while hyenas hustle below.
However, the hyenas can still have the last laugh. The study noted 39 cases of hyenas running off with food that leopards accidentally dropped from trees.
Also, trees offer little protection against robbers that climb, like lions and male leopards. While lions claim only one-tenth of thefts, male leopards commit four times that, stealing mostly from female leopards. The result surprised Balme, but he thinks that male leopards can easily spot another leopard eating in a tree across the plains. "Male leopards patrol large territories. Females feeding in a tree for several days makes it more likely for males to find them."
I'm pretty convinced [that avoiding food theft] is the primary reason for leopards hoisting their kills
For the female leopards, a lost kill extorts more than a few days' hunger. The more kills a female has lost, the fewer cubs she could raise.
Balme's study shows that leopards hoist their prey in response to the immediate threat of a competitor. In Botswana, where hyenas also reach high numbers, leopards hoist almost 40% of their kills. Where there are fewer competitors or thicker vegetation to hide – as in India – leopards hoist less often.
There are several other potential reasons for leopards to hoist their prey. For example, a hoisted prey might spoil slower, or allow the leopard to hunt elsewhere then return to feed. But Balme found little or no support for these alternative explanations.
"I'm pretty convinced [that avoiding food theft] is the primary reason for leopards hoisting their kills," says Balme.
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