What do you think of when you hear the word “tortoise”? The giant tortoises that lumber along like tanks over the Galapagos Islands in the Pacific and the Seychelles in the Indian Ocean? The gopher ...

It would be a memorable sight. But it would also be so wrong to tip over Galápagos giant tortoises to see how shell shape affects their efforts to leg-pump, neck-stretch and rock right-side up again.

Millions of years ago, before the Southwest was a desert, the Las Vegas Valley had lakes, marshes and streams that fed plentiful vegetation and animal life, including desert tortoises. As recently as ...