The second in line to the British throne visited an elephant sanctuary, where he met Ran Ran, a 13-year-old female elephant who was discovered in 2005 with a leg wound caused by an iron clamp trap.
Handed carrots by the animal's keeper, William passed them to Ran Ran, who reached for more with her trunk even while her mouth was crammed full.
The visit to Yunnan province, a tropical region bordering Myanmar and Laos that has been the focus of government efforts to stop poaching and reduce conflicts between people and elephants that eat their crops, was organised for William to learn how Asian elephants are surviving in the wild.
William, who regularly speaks out against wildlife trafficking, was expected to bring up the plight of African elephants, tens of thousands of which have been slaughtered in recent years to meet a surging appetite for ivory in Asia, primarily China.
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Last week, China banned ivory imports for one year in the hope that it would help reduce the demand for African tusks and protect wild elephants.
China's illicit trade in ivory began to explode in 2008, when Beijing was permitted to purchase 62 tons of ivory under the Convention on International Trade of Endangered Species.
The purchase was presented as a way to keep China's traditional artisan ivory carving industry alive.
After legal pieces started showing up in shops, it soon became a status symbol in China. Carved ivory has historically been highly prized in China, and its scarcity has turned it into an investment choice akin to gold and silver.
During their meeting, Xi explained China's policies and work protecting elephants and other wild animals and told the prince that he hopes to strengthen international cooperation in this field.
William arrived in China on Sunday after a four-day trip to Japan. In Beijing, he met Chinese political leaders as well as young people from disadvantaged backgrounds, another issue close to his heart.