What is the Bullfrog Control Dilemma?

Every year, around the beginning of July, Fraser Valley residents start to hear the sound of invasive predators in their local wetlands. The loud “barrum barrum” mating call of the American Bullfrog (Lithobates catesbeianus) is certainly a distinctive sound.

 

 

If you haven’t heard this bellowing call, consider yourself (and your local wildlife) lucky. Bullfrogs are invasive, meaning they are not indigenous to this area and are causing ecological harm. Native to Eastern Canada and the United States, Bullfrogs are not part of the natural ecosystem of the Fraser Valley. Bullfrogs reproduce quickly and can grow so big that natural predators (like herons, otters, hawks, and snakes) are less likely to try to eat them.

 

So, why don’t we just remove the Bullfrogs? Unfortunately, the situation is much more complicated than it seems.

There are two things you absolutely need to know:

Trying to control Bullfrogs can result in harming native species rather than helping them

The best thing we can do is leave Bullfrogs alone and focus instead on creating healthy habitats for our native species

 

Read on to learn more about the three major issues surrounding Bullfrog control in the Fraser Valley: Identification, Population Dynamics, and Purpose.

Issue 1: Identification

Local frogs are frequently misidentified as Bullfrogs. Often, people think they are controlling Bullfrogs when they are actually euthanizing native species instead.

The Western Toad, a species at risk, is one of the most common species accidentally euthanized. A large adult Western Toad could go on to make 20,000 tadpoles each spring. A person removing a single adult Western Toad does much more damage to the population than a Bullfrog could have done.

Identification becomes even more difficult when dealing with egg masses, tadpoles, and juveniles. At these life stages, Bullfrogs look very similar to native species in shape and size.

 

Key takeaway: Never engage in species control efforts without first consulting an expert. Harming native amphibians is not only detrimental to the local ecosystem, it is against the law under the BC Wildlife Act.

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Issue 2: Population Dynamics

Bullfrogs, like our native frogs and toads, hunt their prey by sensing movement. If they determine the potential prey item will fit into their mouths, they will try to eat it.

This means that Bullfrogs can be cannibals, eating their own young. This is an important component of Bullfrog population dynamics: large adult Bullfrogs help to control populations by eating younger Bullfrogs. Studies have shown that removing only adult Bullfrogs from an area will actually increase the number of Bullfrogs in the population overall, as more small Bullfrogs survive to adulthood.

In order to successfully control Bullfrog populations, a multi-life stage removal approach must be undertaken. Professional training is required to differentiate between different amphibians’ egg masses, tadpoles, and juveniles. This type of control program requires a comprehensive management plan. 

Key takeaway: Removing Bullfrogs from a population can actually cause an increase in the overall number of Bullfrogs in future years. If you try to remove multiple life stages, your odds of accidentally harming native species increase drastically.

Issue 3: Purpose

Before we try to solve this Bullfrog control dilemma we must ask ourselves why we are engaging in Bullfrog control. Given all of the risks, is Bullfrog control really worth it?

The solution to the Bullfrog control dilemma is counterintuitive to how we typically manage invasive species. Removing Bullfrogs is not the answer. Once Bullfrogs are established in an area they are nearly impossible to eradicate. Bullfrogs can migrate over four km on land, meaning your property will continue to be re-infested with Bullfrogs shortly after you remove them.

The purpose of any invasive species management program should be to help native species and ecosystems flourish.

Do not focus on the Bullfrogs! Instead, focus on what native species need to thrive. Ponds, wetlands, and streams with riparian vegetation. Access to shrubs and forests. Pesticide-free areas to travel through. Insects and rotting logs. Woody debris in the water to use as hiding places and as anchors for their egg masses.

The best way we can help native species and ecosystems is to create, enhance, and maintain healthy, connected habitats.

Conclusion

Here at the FVC, we encourage residents of the Fraser Valley to learn about the ecosystems in their neighbourhoods. Get to know the insects, birds, and amphibians that reside there. Learn about what these species need to thrive, and work towards restoring healthy habitats for all creatures. Bullfrogs will never be eradicated from the Fraser Valley. We do not recommend individuals engage in Bullfrog control without a comprehensive management plan in place. Instead of focusing on Bullfrog control, we recommend working towards ensuring our native species have the habitats they need to survive the many threats they face, including climate change.

 

Are you curious about how your property could better support nature? Check out our Nature Stewards program for more information.

 

If you have a frog observation and would like more information, submit your sightings to Frog Finders.

 

For more information about the Fraser Valley Conservancy’s approach to Bullfrog management please send us an email.

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