For the past decade, poachers have killed rhinoceroses in the wild and in protected reserves around the world at alarming rates, threatening the survival of four of the world's five rhino species.
The poaching is driven by a demand for rhino horns in southeast Asia that has grown nearly insatiable; so much so, experts say, that any living rhino - anywhere in the world - is now at risk of being killed.
Perhaps no rhino death illustrates that threat more forcefully than the killing of Vince, a 4-year-old male white rhino who was slaughtered this week inside his enclosure at a zoo outside Paris. The rhino - discovered by his keeper at the Thoiry Zoological Park today - now holds the ominous distinction of likely being the first rhino to be killed by poachers inside a zoo, experts said.
"This is the first time we've heard of it," said Crawford Allen, senior director of Traffic North America, a regional office of the World Wildlife Fund (WWF).
"It's certainly the first time it's happened in Europe.
"It's an incredibly shocking and distressing occurrence," he added. "It's also a game-changer for zoos. They've woken up today and realised their world has changed if they have live rhinos in their collection."
In a statement posted on Facebook, the Thoiry Zoological Park, which is 50km west of Paris, said its "entire staff is extremely shocked" by Vince's killing. The animal was born in a zoo in the Netherlands in 2012 and arrived at Thoiry in March 2015, the zoo said.
The zoo pinned the killing on criminals who forced open an outer gate outside the rhinoceros building overnight. The intruders then forced open a second metal door and broke open "an intermediate inner door" that allowed them access to the animal lodges, the zoo said.