Southern Pacific Rattlesnake
Crotalus oreganus helleri
The Southern Pacific rattlesnake is a pit viper, meaning that it has deep pits between the nostril and the eye on either side of its head. These pits open into highly sensitive infrared detecting organs, with which the snake can “see” the warmth radiating from potential prey. While rattlesnakes are venomous, they are not normally aggressive toward people. If you encounter one basking on the trail, give it some space and it will slither away.
Pit vipers like this one can essentially "see" infrared through the pair of pits located between their eyes and nostrils.
What’s for Lunch:
Birds, small mammals, lizards, frogs, other snakes, and insects
Coastal dunes, coastal sage scrub, grassy areas, and chaparral