"Tusked elephants breed less than tusk-less ones due to poachers" (63 chars)

You are just describing how an evolutionary response works, not being more accurate.

I would specifically argue that the word "response" is itself contextually inaccurate, in the sense that it triggers ambiguity as to whether the change in reproductive rates is _intentional_ or not. My headline removes that ambiguity.

A different attempt: "Tusked elephants breeding less than before due to poachers. Tusk-less ones unaffected" (85)

“Tusk-less elephants outbreed tusked ones”

But that wouldn’t be as catchy and as misleading/misunderstood as the original. Anyone reading that one will assume that elephants are purposefully being born without tusk, but it’s just a ratio consequence of tusked elephants dying early.

You did not mention poachers' potential impact.

“- due to poachers”

"Poachers cause evolutionary benefit for tusk-less elephants"