Underwater look at invasive clawed frogs
Scientist explains how invasive amphibians can harm native species and habitats
The African clawed frog (Xenopus laevis) is a semi-aquatic frog native to sub-Saharan Africa that readily acclimates to a wide range of habitats. These frogs can take over a habitat, and either out-compete or consume native species of frogs, fish, and other wildlife. African clawed frogs are often carriers of diseases that are harmful to amphibians and fish. Their ability to rapidly reproduce and spread make them a significant conservation concern.
Learn more about African clawed frogs and their threat to native species in this interview with Dr. Max Lambert, a research scientist at the Washington Department of Fish and Wildlife (WDFW). Special thanks to Marie Tweedy from King County Department of Natural Resources and Parks for their help conducting the interview.
Are African clawed frogs in Washington?
Unfortunately, yes. Although there isn’t any direct evidence on how African clawed frogs were introduced in Washington, our Department believes the frog populations were initially established from people dumping aquarium pets into ponds, which is a common practice with other aquatic invasive species.
After receiving reports from contractors, people fishing, and other community members, WDFW has confirmed clawed frogs in three cities in Puget Sound since 2015: Bothell (King County); Issaquah (King County); and Lacey (Thurston County). However, there hasn’t been any broad-scale, systematic survey to identify additional populations in the state, so it is possible clawed frogs are prevalent elsewhere.
African clawed frogs seem to become abundant quickly in human-created stormwater ponds. Although these ponds can also make good habitat for native species, clawed frogs may start to push out native species and make it harder for these species to exist in our residential and urban areas.
Please note: African clawed frogs are classified as a prohibited species in Washington, meaning they may not be possessed, purchased, sold, propagated, transported, or released into state waters.
What are some characteristics of the African clawed frog?
The African clawed frog does not look like a stereotypical frog we see often in European American media, and it rarely ever leaves the water. With olive to brown skin, often with blotches or spots, African clawed frogs do not have eye lids, tongues, or vocal sacs. Their front feet are unwebbed while their back feet are fully webbed with black, sharp claws.
Mature females average larger than males, growing to larger than an adult human fist. Larvae (tadpoles) look like a small catfish, and their most prominent feature is a pair of long thing barbels that extend from each side of their chin.
Unlike native frog species, African clawed frogs are very resilient and can live in a diversity of types of water bodies ranging from polluted stormwater ponds to small streams. However, they are freshwater frogs, so you won’t find them in Puget Sound or in rapid, white water.
Why do these frogs have claws?
The claws these frogs have are like fingernails — and how they use these claws is not always clear. Some believe claws are used to scratch predators, which is likely true. Their claws certainly can hurt! But the primary use of these claws is likely to shred food, which could be a decaying carcass, another frog species, fish, bird, snail, or anything else they can fit in their mouth. In fact, their claws help them eat other frogs and fish that are bigger than them because they can tear their prey into smaller pieces.
How do African clawed frogs threaten native species and habitat?
African clawed frogs harm native ecosystems by competing with and preying on native species. They also have the potential to introduce harmful pathogens that hurt native fish and amphibian populations. African clawed frogs have a long life span, an extended breeding season, and are prolific reproducers. They can even survive severe drought and freezing conditions!
Can these invasive frogs be removed?
This is something we’re trying to figure out, and it’s definitely a big challenge! We’ve tried to remove clawed frogs from a stormwater pond in Lacey. However, one of the challenges we faced was that the stormwater pond was connected to pipes, which meant that even after draining the pond and using poison, clawed frogs were able to recolonize the pond since they were hanging out way up in the pipes.
One technique we have used that has worked well is creating double layers of knee-high cloth fencing around ponds with clawed frogs. This stops the frogs from leaving and prevents them from colonizing a new area.
WDFW is collaborating with partners to figure out best practices to control and manage clawed frogs to prevent them from colonizing across the state. The City of Lacey has been an integral partner since the first detection of clawed frogs there. WDFW is developing more great partnerships with the Washington Invasive Species Council, City of Issaquah, Professors at St. Martin’s and Pacific Lutheran universities, USGS, Trout Unlimited, and others.
Thank you to all of our partners who are helping us figure out best practices to control and manage clawed frogs and prevent them from colonizing across the state.
How can I help prevent the spread of invasive species?
The number one thing people can do to help prevent the spread of invasive species like clawed frogs is to never let a pet go in the wild! As the Washington Invasive Species Council says, “Don’t Let it Loose!”. Never release a frog, fish, turtle, crayfish, or other animal or aquatic plant into the wild, such as rivers, streams, lakes, or stormwater ponds.
The next major thing people can do is to share the Washington Invasives mobile app with your friends and family. The Washington Invasive app allows you to easily report possible invasive species sightings with just a few taps on your phone. Information submitted to the mobile app goes directly to our Aquatic Invasive Species Unit. Even if you’re unsure about the species identification, send in your observation and we’ll be able to figure it out and follow up as needed.
How do I report a possible sighting?
I discourage anyone to go out of their way to look for clawed frogs, as proper surveying requires special tools, equipment, and a permit to protect native wildlife and habitat.
It’s better to keep your eyes open and if you happen to see a frog, take a picture of it and share it with us if you suspect it could be invasive.
If you observe African clawed frogs or any other known or suspected aquatic invasive species, please report your sighting.