Though neither animal is endangered and the hunt is legal, it has caused some critics to accuse William of double standards and say it weakens his image as an animal rights activist, ThinkSpain reported.
"The Duke of Cambridge has for many years been a passionate advocate for endangered wildlife and has campaigned tirelessly to help stop the illegal poaching of rhino horn and elephant tusk. His track record in this area speaks for itself," a royal spokesman said.
William and Charles made the joint plea to protect endangered animals for the start of a week of wildlife conservation activities by the royal family, the BBC said. The week is scheduled to end with them attending a conference in London on the illegal wildlife trade.
"This year, I have become even more devoted to protecting the resources of the Earth for not only my own son but also the other children of his generation to enjoy," Prince William said in his televised plea.