[9] When not underground, they seek litter or vegetation (particularly tules) to use as cover from predators and environmental extremes, and they avoid rocky or otherwise open areas.

[4] Due to their predominately aquatic lifestyle, giant garter snakes prey upon fish, frogs, and tadpoles.

[11] Starting in March to mid May, male giant garter snakes emerge from hibernation search for a female to mate with.

Males were observed to have a decreased body condition during early spring, as a result of allocating energy towards mate searching and reproductive opportunities, forgoing growth and feeding.

[13] Giant garter snakes are ovoviviparous, meaning they carry eggs internally but give live birth.

Following the spring mating season, birthing occurs from mid July to early October[13] with average litter size of 17 young.

[4] The giant garter snake has fared better in the Sacramento Valley because rice cultivation and the associated canals have provided habitat.

[16] Attempts are underway to restore artificial wetlands to provide quality habitat for the giant garter snake, but it is too early to know if these efforts will significantly aid the recovery of this threatened species.

In addition to habitat loss and fragmentation, introduced predators such as the American bullfrog and the northern water snake may also be suppressing recovery.

[18] Adult giant garter snakes will commonly eat bullfrog juveniles and tadpoles, which may put them at increased risk for parasite contraction.