The Northern Pacific rattlesnake (Crotalus oreganus) frequently occurs in wildlife- urban interfaces in coastal California. Rattlesnakes are out of brumation from April to October, often basking when humans are likely to be recreating. For some species, such as Eastern gray squirrels and Western fence lizards, increased exposure to humans results in habituation to human presence and decreased antipredator behavior. This study examines if increased exposure to humans results in decreased antipredator behavior (i.e., rattling, flight) for the Northern Pacific rattlesnake, therefore, increased risk for both humans and snakes. We are quantifying antipredator behaviors of the Northern Pacific rattlesnake by measuring Alert Distances (ADs) and Flight Initiation Distances (FIDs) of individuals encountered on a reserve closed to the public. During each measurement, snakes are photographed for identification, allowing us to track the number of encounters with each snake. Preliminary results suggest decreases in AD and FID with increased temperature, and increases in AD and FID with increased snake age/size and human exposure. Continued data collection will allow us to better quantify AD and FID for snakes with increased exposure to humans, and thus assess the need for managing risk in recreational areas with dense populations of the Northern Pacific rattlesnake.