[hinckley buzzard]

its sheep have remained genetically isolated, and no other sheep have been brought in for breeding,

75 years of in-breeding creating more and more runt offspring.

[Dilbert San Diego]

And the smaller sheep who didn’t survive in the past are now surviving to adulthood. Isn’t that a good thing, that more survive because the winters aren’t as harsh????

[rod1]

You nailed the real reason!
I think you should get Freepers Points for the correct answer.