Many years ago, my father and I hiked through Big Bend in Texas. It’s a national park now, but in those days it was rough country.

One night we were rolling out our sleeping bags when a couple with a dog asked if they could camp nearby. We welcomed their company and turned in for the night. They tethered their dog to a stake beside their tent.

Some hours later my father nudged me awake and turned his flashlight into the darkness. Illuminated by the light, we saw pairs of yellow eyes peering out of the shadows. A pack of snapping and snarling coyotes were closing in on the dog. Although we chased them off and our neighbors put the dog in their tent, we slept fitfully.