The question in the title is pretty well redundant today because you will see many videos on YouTube and on other video websites showing lions successfully attacking and killing both adult and sub-adults giraffes. It said that the main predator of giraffes is the lion and that more than half of giraffe calves fail to reach adulthood because of lion predation.
That conclusively answers the question so I will expand the answer a little by stating that lionesses hunt cooperatively in behaving as rugby players “by division of labour, with the left and right wings circling the prey and the centers lying in a position from which they could capture prey fleeing from the wings.”
Lions knock down large prey animals such as wildebeests and zebras with the impact of their body or they are grabbed and dragged down. The giraffe is killed by a bite to the throat which results in strangulation or it is suffocated with a nose bite.
Sometimes lions hold the nose of the prey animal with one paw while pulling the head down to the chest. This breaks the neck of the animal when it falls. There are also reports of lions “hamstringing buffalo and giraffes”. The information for this information comes from a variety of sources including Wildcats of the World which refers to, for instance, Simba: the Life Of The Lion by C.A.W. Guggisberg 1963.
In the Kruger National Park giraffes feature quite strongly in a long list of prey items in the diets of African lions in which the wildebeest is the top prey animal. In a full list of prey animals of the African lion, in Wild Cats Of The World, under the title “Occurrence of prey items in the diets of African lions (percentage of kills), the giraffe is listed under Kruger National Park at 3.9%. The wildebeest ranks at 23.6% and the impala at 19.7% (in Kruger National Park).
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