Invasive Bullfrogs Threaten Arizona Garter Snakes

The U.S. Fish and Wildlife Service identifies bullfrogs as a critical threat to the native northern Mexican garter snake.

Updated on Oct. 29, 2026 in Reptiles

Gouache-painted illustration of a large bullfrog and garter snake in an arid desert wetland, conveying environmental risk. — Invasive bullfrogs, introduced to Arizona decades ago, are now identified as a primary driver in the decline of the endangered northern Mexican garter snake. AI Illustration. Upload story photo >

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Non-native bullfrogs are decimating populations of northern Mexican garter snakes across Arizona by preying on young snakes and competing for resources. Studies reveal that these invasive frogs are now linked to significant physical trauma observed in the snakes.

Why it matters

The spread of bullfrogs poses a dire risk to the northern Mexican garter snake, which currently occupies only 10% of its historical habitat. These predators also carry the chytridiomycosis fungus, further endangering native species like the Chiricahua leopard frog.

A female bullfrog can produce up to 20,000 eggs per clutch, drastically outpacing the average brood of 13.6 young produced by a female northern Mexican garter snake. Management crews mitigate this by using 30-foot seine nets and .22-caliber rifles.

The players

U.S. Fish and Wildlife Service

This federal agency is responsible for the management and conservation of fish, wildlife, and natural habitats across the United States.

State Game Department

This state organization oversees the regulation of wildlife and hunting practices within Arizona.

The details

Bullfrogs were introduced to Arizona in 1926 for sport hunting, but they now compete for native prey and actively hunt young garter snakes. Land managers are responding by draining cattle tanks and conducting targeted control programs in areas like Scotia Canyon.

Arizona introduced bullfrogs for sport hunting and food in 1926.
Control programs for bullfrogs began in southern Arizona during the 1990s.
The Chiricahua leopard frog was officially listed as threatened in 2002.
Conservationists introduced leopard frog tadpoles to Scotia Canyon in 2009.

Culture Shift

The aggressive removal of invasive species reflects a growing shift toward active ecological management to correct historical environmental errors. This approach marks a departure from earlier policies that prioritized introducing non-native game species for sport and food.

Residents and hikers in areas like Scotia Canyon may encounter increased wildlife management activities, including drainage of cattle tanks to control invasive populations. These efforts are essential to preserving the remaining 10% of the garter snake habitat in the state.

The takeaway

The struggle to balance invasive bullfrog populations with native snake health highlights the lasting ecological consequences of historical species introductions. Property owners near habitats should support local land management programs aimed at mitigating the spread of these invasive frogs.