The gray fox (Urocyon cinereoargenteus) is an under-studied species in North America. Here we provide data gathered through observations over 17 d at a gray fox den in San Mateo County, California. We recorded prey indices through direct observation, as well as through indirect observation with photos recorded by motion-triggered cameras. The largest prey was a mule deer fawn, which we determined was killed by a gray fox. This finding is the first record of gray fox predation on mule deer. Lagomorphs and rodents formed the majority of prey items. We also recorded behavior that both contradicted and corroborated previous literature. We observed the male bringing food items to the den, a behavior that previous researchers have disagreed about. We also observed allogrooming between the adult pair, as well as one instance among pups where leg-lifting accompanied by presentation of the genitalia was clearly used as an aggressive dominant behavior rather than a submissive behavior, as reported in previous literature.