Invasive Frogs Devastate Arizona Gartersnake Populations

Native to the eastern United States, American bullfrogs were introduced to Arizona starting in the 1920s with the intention of providing a food source for hunters and anglers. However, these highly reproductive and adaptable amphibians have become a significant threat to native wildlife, particularly the northern Mexican gartersnake.

These native gartersnakes, which depend on wetlands, are now facing severe population declines due to bullfrog predation and competition. Adult bullfrogs are opportunistic predators, consuming native amphibians, reptiles, birds, and small mammals. Juvenile bullfrogs also compete for resources, impacting the survival of young gartersnakes and their reproductive success.

Federal assessments indicate that northern Mexican gartersnakes have vanished from or exist in critically low numbers across approximately 90% of their historical United States range. Remaining populations in Arizona and New Mexico are now fragmented. Efforts to control bullfrogs include netting, trapping, and draining affected wetlands, with some successes like the eradication of bullfrogs at the Cienega Creek complex leading to native leopard frog population increases.

Bullfrogs are highly mobile, with individuals recorded traveling significant distances, making eradication efforts challenging. Their ability to spread through newly formed pools during wet weather complicates containment. Despite these difficulties, conservation teams, state wildlife agencies, and federal partners have been working since the 1990s to reduce bullfrog numbers in critical habitats for native species.