Agostino Paravicini Bagliani, the author of “Il Bestiario del Papa” (The Pope’s Bestiary), said that for many centuries popes had used animals, like the dove, “to create and confirm the authority and sovereignty” of the papacy, a reinforcement of its power. It was unclear, however, exactly how many popes had domestic pets, he noted; the most famous is Pope Pius II, who lived during the Renaissance and wrote about his dog, Musetta.

Other Renaissance popes also had pets, notably Paul II, who had a monkey; Sixtus IV, who had an eagle; and Leo X, who had a menagerie of exotic animals, including lions, leopards and bears, Mr. Paravicini Bagliani said.

He also cited a famous photograph of Pius XII with a goldfinch perched on his finger.

Pius VI kept a dog, Diana, at the summer papal residence in Castel Gandolfo.

Francis, too, has demonstrated that he respects and cares for animals.

In his 2015 encyclical on the environment, “Laudato Si’,” or “Praise Be to You. On Care for Our Common Home,” for example, he repeatedly pointed to interconnectedness of humans and all creatures.

“Because all creatures are connected, each must be cherished with love and respect, for all of us as living creatures are dependent on one another,” Francis wrote.

And during his papacy, he’s petted a number of animals, mostly dogs.

On Wednesday, Francis said the world was experiencing “an age of notorious orphanhood” that could be countered, in part, by caring for children, either through adoption or naturally. “It is riskier not to have them,” Francis said. “Think about this, please.”

One animal rights group said it wasn’t an either/or situation.

“It is strange to think that the pope considers love in our lives to be limited in quantity, and that giving it to someone takes it away from others,” said Massimo Comparotto, the president of the Italian branch of the International Organization for the Protection of Animals.

“Perhaps the pontiff is unaware of the enormous sacrifices that volunteers endure” to help save animals, he said in a statement. “Anyone who thinks that life is sacred loves life beyond species,” he said.