Prince William: Prince George "has a voice to match any lion's roar"

Prince William and Kate's little prince apparently has a good set of lungs on him.

William joked about the couple's seven-week-old son, Prince George, during a speech at Thursday's Tusk Conservation Awards in London.

"As you might have gathered, Catherine and I have recently become proud parents -- of a baby who has a voice to match any lion's roar!" the 31-year-old said. "This is actually our first evening out without him, so please excuse us if you see us nervously casting cheeky glances at our mobile phone to check all is well back home."

Thursday's awards ceremony was Kate's first formal event since giving birth to George on July 22. William, who is patron of the African conservation charity Tusk Trust, handed out two awards at the event and championed the evening's cause in his speech.

"Like any new parents, our thoughts inevitably turn to the world that our child will inherit," he told the crowd. "It is unfathomable to imagine a world in which children who have been born in the past couple of months may grow up in a world in which rhinoceros have ceased to live in the wild."

William noted that 35,000 elephants had been killed for their ivory in the last year alone. "The possibility of extinction is bad enough for one of our children growing up here in the West, who never experience the magic of seeing a rhino; or even for my own little George, who Catherine and I very much hope to introduce to east Africa -- a place we know and love -- in the fullness of time," he said. "But for a child growing up in Africa and whose birth-right and economic inheritance these creatures are, it is nothing more than immoral that he or she may never experience what his parents and grandparents knew and treasured."

The gala took place on the same day it was announced that William is ending his military career to focus on royal duties and public service.