You might remember Cecil the Lion, who was the male leader of his pride, but was killed by a big game hunter.
Now some scientists are speaking out, saying the American version of the lion, the mountain lion, is also at danger.
The Safari Club International Convention brings more than 20,000 big-game hunting enthusiasts to Las Vegas, with one of the main events being an auction for hunting excursions around the world.
The auctions include the opportunity to kill African elephants and Alaskan bears.
Trophy hunting has become increasingly controversial, especially since Cecil the Lion's death in 2015.
A counter convention was held at the Luxor, with scientists and animal activists saying they wanted to be an alternative voice for trophy hunting.
Scientists at the counter convention also said they conducted research that shows just how much trophy hunting has affected people living in Southern Nevada.
The Humane Society says they gathered unique data from all states that allow mountain lion hunting. Nevada doesn't have a large population of mountain lions, but that makes it even more concerning for those wanting to preserve its species.
"That has huge conservation concerns for this animal,"says Wendy Keefover with the Humane Society of the United States.
The problem is, since mountain lions are not native to southern Nevada, that means they are fleeing or escaping from other areas, like California, where they are hunted or facing infanticide within their pack.
To escape this, they are willing to live anywhere, and feed on anything.
"If you're constantly killing the adult stable animals in the system, you create social chaos, and that's what's happening in Nevada," says Keefover.
That means, since big game hunters are killing mountain lions, and forcing them out of their natural habitat, they are being found in people's backyards, feeding on their livestock, or even people's pets.
"Killing the dominant males doesn't solve anything, all it does is exacerbate and cause a lot of problems," says Rob Wielgus, the Director of Large Carnivore Conservation Lab at Washington State University.
Activists will be holding a rally in support of Cecil the Lion, and what they call Cecil 2, meaning the mountain lion, in front of Mandalay Bay on Saturday from 10 a.m. to 2 p.m. It's part of a global initiative to speak out against trophy hunting. There will be similar rallies planned across the country.
A spokesperson for the Safari Club International said in a statement, "We fully support the right of protest, but what protestors at this convention should understand is that it would be much more effective to partner with us in conservation than to fight against us."
They went on to say the club has spent $60 million since 2000 in conservation, wildlife education, and humanitarian services.