As for who to call? LOL, the 12 year old boy next door is probably the quickest to respond, but animal control or animal rescue would be the proper authorities.
FLATHEAD SNAKE:
Natural History: Probably nocturnal and found mostly in spring and autumn under rocks, logs, and other moist debris in forest or brushy slopes. Burrows deeply as surface soil dries in summer. Sometimes found on or along roads at bottoms of rocky hillsides. Mates in April and May and deposits 2-4 eggs in moist soil or under rocks during June. Young hatch in September at 7-0 cm TL. Eats scorpions, spiders, centipedes, and a variety of other small arthropods, which it probably tracks by scent.
VENOMOUS ALERT... SORT OF...
Two small, grooved rear fangs and small venom glands are apparently used in subduing prey, but the snake is no threat to human beings and does not bite when handled. Preyed upon by birds, small mammals, lizards, and other snakes.
"Rear fangs" means the teeth are in the back of the mouth, and would be nearly impossible to bite human skin, break the skin, and get ANY venom in the bloodstream... and even if it did, it's only strong enough to kill insects, not humans.
I'm assuming you aren't suggesting we use him as a control group to find out if it (New Mexico Banded Rock Rattlesnake) is poisonous? :0)
Pookie & Me