Young rattlesnakes do not yet have their rattles, and since they are hard to see, they are as dangerous as adults, according to the National Park Service at Yosemite. Furthermore, some adults may lose their rattles, so it is a good idea look out for the triangular head. And, especially in Folsom Lake and Auburn SRAs, where a percentage of the rattlesnakes don't rattle at all.
The snake season is here, so beware, the snakes are leaving their dens and looking for something to eat and bask in the sun. Hikers should be wearing boots and long loose pants; mt. bikers slow down so you don't run over them (and get bit in the process), dog walkers KEEP THOSE DOGS SAFE AND ON LEASH, and equestrians should really listen to their horses who can hear and smell them way before their riders can.
Most people bitten by rattlesnakes have inadvertently stepped or ridden over them. Snakes detect movement by sensing vibrations in the ground. Their eyes see well even in low light. Rattlesnake bites can be dangerous but are very rarely fatal to humans. With proper medical treatment, including antivenin, bites are usually not serious.
After the rattle, rattlesnakes’ most distinctive physical feature is their triangular head. Also, they have vertical pupils, like cat’s eyes. Remember, natural selection has benefitted snakes that don't rattle. Watch for that triangular head.
Generation after generation of rattlesnakes will use the same dens, sometimes for more than 100 years. Upon leaving their dens, they like to sun themselves on rocks and other open places. Though they are not nocturnal, in the hot summer months they may be more active at night.
Despite their venom, rattlesnakes are no match for California King snakes, which are fond of putting them on their dinner menus. DON'T KILL CALIFORNIA KING OR MOUNTAIN KING SNAKES! (pictures below the rattlesnake.) THANKS TO STEPHANIE FOR THE NEW PICTURE AND INFORMATION.