As I said, after the initial bolting away from it, I'm more than sure they'd shoot
as you say, while shes munching she's a open target.
You could also be picky, one gun shot can be enough to scare away any big cat, the hundreds of rounds going off she'd probably bolt for the nearest exit or some sort of hiding hole, or she could go into a mass panic'd rage at which point anything that moves would be considered a threat. It's the same principle if you have a dog during firework night, you let the dog go hide, don't be stupid enough to try and get them out
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I find it funny you call it ridiculous, yet you didn't quote me to tell me your opinion. Maybe hoping I didn't actually see it to tell you why it's wrong?
As the other guy mentioned, a tiger would be far out of the norm, short of being a veteran poacher or hunter (even then I'm dubious), if something that big, that vicious comes behind you, surprises you, you would not stand your own ground at all. You fight or flight system would kick in, you're adrenaline levels would soar and you'd be running before you even clicked you were holding a gun and she was stationary.
But hey, I'm just a Zoologist / Biologist with countless hours logged working in close proximity to animals like this, what would I know?
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Just to be nit picky, they did address that earlier on in the season mentioning her dietary requirements and maintenance to look after her (Not to mention he's her former keeper so he's not a complete idiot who came across a cub and threw a chain on it), malnourished a bit maybe, near death? nah, she'd eat Ezekiels face before she got to that stage.
Tbh I think the show has worked her in quite nicely, when I first found out about it I thought it would be over kill, tiger this, tiger that etc