Can a German shepherd kill a cougar?

it can it it wants to. it depends on the environment. if it feels intruded, it will instinctively react. otherwise, it's as harmless as a baby chihuahua.

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I'm going to say yes, and here's why. Firstly, most dogs can. If they bite hard enough to cut through your trachea, it's possible you could die if untreated. Larger dogs could more easily do this.

Normally, however, if dogs are trained correctly not to bite, even German shepherds can be kind and caring.

So yes, they have the physical capability to do so. Would they? Only if untrained and provoked enough.