I found this young Blacktailed Rattlesnake resting under the dried-out husk of a small mammal (skunk?) in a cave near Phoenix on a survey of lands managed by Desert Foothills Land Trust.

In wet years, this small cave fills with water from a few inches to around a foot deep. It becomes putrid slop, full of javelina feces and dozens of animals hiding from the heat. This small mammal had died in that water, eventually settling against this wall. This summer, the cave was bone dry. But, the dozen or so rattlesnakes that aestivate here each year still showed up.