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Hank Green:
    Welcome back to SciShow News.
    Now it's not often that a wild animal makes the headlines, let alone headlines all over the world and for days on end, but that's exactly what's happened with Cecil, an African lion who was killed by a trophy hunter on July 1 outside the border of Zimbabwe's Hwange National Park. Although trophy hunting is legal in Zimbabwe, Cecil seems to have been killed illegally because the thirteen-year-old lion was reportedly lured beyond the park's boundaries with raw meat and the hunters didn't have a legal permit. But for scientists, the lion's death was especially tragic because Cecil was a celebrity of wildlife biology. Researchers from the University of Oxford have been tracking him since 2008, when he was just five years old. By the time he died, Cecil was one of the most thoroughly studied cats in Africa, and thanks to him, we know several reasons why the death of one big cat can be a big deal.

    For one thing, lions are in trouble -- not as much as, say, black rhinos or mountain gorillas, which are facing imminent extinction, but according to the International Union for Conservation of Nature, lion numbers have dropped 40 percent in just twenty-one years. How do scientists know? Well, because for two decades, they've been monitoring 47 separate subpopulations of lions in Africa and India. in 1993, there were 9,310 lions in those groups; last year there were 7,468. Based on those figures, scientists estimate that there are at most 30,000 lions in the world today, whereas in the early 1990s, that figure was closer to 100,000. So scientists know lions are in trouble because they've been studying lions like Cecil. 

    Another thing to consider with Cecil's death is that because of lions' behavior, killing a male lion is essentially killing his offspring too. You've probably heard that lions live in prides, groups of females and their cubs with a couple of males who hang around to mate and defend the territory. Well, Cecil was part of two prides, forming a community of six females and a dozen cubs, and wildlife biologists say that once the dominant male of a pride is gone, it's usually just a matter of time until another male comes in and kills his cubs. That's because the number-one mission of your typical male lion is simply to create as many offspring as he can, and having the cubs of a competitor around means less food and less attention for his cubs.
    Now, a wildlife charity in Zimbabwe has been widely quoted as saying that Cecil's cubs will probably be killed by Cecil's so-called "brother," another male in his pride named Jericho, but the Oxford scientists who studied them both say that that probably isn't the case. What's more likely, they say, is that some other, younger males will move in and eliminate Jericho and the cubs. As the Oxford team recently put it, "Lion society makes 'Game of Thrones' look tame." So Cecil's death may eventually result in the loss of fourteen lions: Cecil, Jericho, and the twelve cubs. That may not sound like a lot, but it's about one percent of Zimbabwe's total lion population.

    Finally, the thing to remember about Cecil is, as the subject of nearly a decade of research, he simply taught us a lot. By tracking and watching Cecil and other lions in Hwange National Park, biologists have made all sorts of discoveries, like that males can strike out on their own at pretty much any age, as young as two-and-a-half and as old as ten, and they learned that some males migrate as much as 200 kilometers to join a new pride. But maybe more than anything, the seven years that researchers spent with Cecil have taught them how fascinatingly complex their lives and relationships are.
    For example, a lot of media attention has focused on Cecil's relationship with Jericho. They're often described as brothers because they lived together in the same pride, as male siblings often do; but they actually weren't related at all and at one time they were mortal enemies. In a sort of obituary of Cecil that the Oxford biologists published this week, they report that, when Cecil was three, his real brother was killed by a rival band of males which included Jericho. It wasn't until four years later that the two met again, but this time Jericho's band was gone because his two brothers had since been killed by trophy hunters. So instead of fighting, the two lone lions paired up and formed what biologists call a coalition, working together in the same pride to fend off rival bands and protect their territory. Now, with Cecil gone, that coalition is gone too, and the balance of power among the park's big cats will change.

    So Cecil's death raises one more question: What does science say about the value or danger of trophy hunting? Well, Dr. David MacDonald, one of the two Oxford biologists who studied Cecil, told the journal Nature this week that the danger is clear enough. Over his years of research, more than seventy percent of the male lions that strayed from the park ended up getting killed by hunters. But he also said that he neither supports nor opposes trophy hunts. He said that sport hunting can be sustainable if it's done with strictly enforced laws that are informed by wildlife science, and that "Our position is to understand the facts... and to support the authorities in enforcing the law."
    Now you probably have opinions about this too. If you do, let us know what you think in the comments below, and if there's science in the news that you'd like to learn more about, let us know here, on Facebook, Twitter, or Tumblr. Thank you for watching, and thank you to this episode's President of Space, SR Foxley. If you want to learn how you could be President of Space or get some other cool stuff, you can go to patreon.com/scishow, and if you want to keep getting smarter with us, just go to youtube.com/scishow and subscribe. 

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