{"id":935,"date":"2025-08-07T10:00:00","date_gmt":"2025-08-07T10:00:00","guid":{"rendered":"http:\/\/audiomateria.com\/?p=935"},"modified":"2025-08-08T19:11:49","modified_gmt":"2025-08-08T19:11:49","slug":"the-us-has-a-bullfrog-problem","status":"publish","type":"post","link":"http:\/\/audiomateria.com\/index.php\/2025\/08\/07\/the-us-has-a-bullfrog-problem\/","title":{"rendered":"The US has a bullfrog problem"},"content":{"rendered":"
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On summer evenings in the Midwest, the muggy air comes alive with a chorus of crickets, cicadas, and frogs \u2014 especially bullfrogs. Their booming mating calls sound like something between a foghorn and a didgeridoo. <\/p>\n

As far as we know, summer here has always sounded like this. Bullfrogs are native to most of the Eastern US, from the Mississippi River to the Atlantic Coast. They evolved here. They belong here. I, for one, adored them as a kid growing up in Iowa, and spent countless summer days trying to catch them to get a closer look. <\/p>\n

What\u2019s unusual is that a few states west \u2014 into Colorado and on to California \u2014 summer nights are similarly marked by the iconic call of the American bullfrog. But here, they don\u2019t belong. They\u2019re unwanted. And they threaten the very existence of some of the West\u2019s other amphibious animals, such as the Oregon spotted frog, which is found only in the Pacific Northwest.<\/p>\n

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American bullfrogs are not native to the Western US. Humans brought them to the region more than a century ago, largely as a food source. And in the years since, the frogs \u2014 which are forest green and the size of a small house cat \u2014 have multiplied dramatically, spreading to countless ponds and gobbling up everything that fits in their mouths, including federally threatened and endangered species. Conservation scientists now consider them among the most dangerous invasive species<\/a> in the Western US, and in the 40-plus<\/a> other countries worldwide where they\u2019ve been introduced. <\/p>\n

That leaves bullfrogs in an unusual position. Invasive species are typically brought in from other countries \u2014 Burmese pythons in Florida<\/a> and spotted lanternflies in New York City<\/a> come from Asia, for example \u2014 but American bullfrogs are, as their name suggests, American. They\u2019re both native and invasive in the same country. And the difference of just a few states determines whether we treat them like pests or as an important part of the ecosystem. <\/p>\n

It\u2019s easy to hate bullfrogs. They do cause a lot of damage and, like other non-native species, they\u2019re leading to what some researchers call the Starbucksification of the natural world \u2014 you find the same thing everywhere you go, which can make ecosystems less resilient. Yet bullfrogs themselves aren\u2019t the main problem, but rather a symptom of a much bigger one.<\/p>\n

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How bullfrogs took over the West  <\/h2>\n

One reason is that people enjoy eating them. Or more specifically, their legs. <\/p>\n

In the 1800s, as the human population in the West surged amid the Gold Rush, so did an appetite for frog legs, which were associated with fancy French cuisine. To meet that demand, people collected native amphibians from the wild, like the California red-legged frog. But as those species became rarer and rarer \u2014 in part, due to overharvesting, researchers suspect<\/a> \u2014 entrepreneurs and farmers started importing American bullfrogs from the eastern US and tried to farm them. <\/p>\n

For a time, it seemed like the bullfrog industry might take off. <\/p>\n

\u201cBullfrog legs! Something to tickle the gustatory glands of the epicurean bon vivants,\u201d a reporter wrote<\/a> in the Riverside Daily Press, a California paper, in 1922. \u201cPropagation of the bullfrog in this state already has become a successful reality. In the near future, bullfrog farming may be expected to take its rightful place as one of the prominent industries of California.\u201d<\/p>\n

That never really came to pass. Bullfrog farming proved challenging and financially risky<\/a>: They take years to raise, they need loads of live food, and they\u2019re prone to disease outbreaks, as Sarah Laskow wrote in Atlas Obscura<\/a>. And for all that trouble, they don\u2019t produce much meat.<\/p>\n

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But while the frog leg industry didn\u2019t spread, the frogs, of course, did.  <\/p>\n

They escaped from farms and, with other accidental and intentional introductions, proliferated until they were common in ponds, lakes, and other water bodies throughout much of the West, including Arizona, California, and the Pacific Northwest. Now, in some portions of the region, \u201cyou see so many bullfrogs that it\u2019s just sort of alarming,\u201d said Michael Adams, an ecologist and amphibian expert at the US Geological Survey, a government research agency that monitors wildlife. There are no reliable estimates of the total population of bullfrogs in the West, though a single pond can be home to thousands of individuals<\/a>.<\/p>\n

Part of what enabled their success is biology: A female bullfrog can lay as many as 25,000<\/a> eggs at one time, far more than most native species. <\/p>\n

But as several researchers told me, humans have also modified the landscape in the West in ways that have helped bullfrogs take over. While western states have rivers and wetlands, permanent warm waterbodies weren\u2019t common until the spread of agriculture and the need for irrigation, said Tiffany Garcia, a researcher and invasive species expert at Oregon State University. Now ponds, reservoirs, and canals \u2014 which bullfrogs love \u2014 are everywhere.<\/p>\n

\u201cIt\u2019s a story of human colonization,\u201d Garcia said. \u201cBullfrogs were brought by people settling and industrializing the West, and they are maintained by people who are natural-resource users of the West. They wouldn’t be here and survive without us changing the landscape to create these systems where they do so well.\u201d<\/p>\n

Bullfrogs are often found alongside other non-native species, Garcia said, which typically tolerate landscapes modified by humans. And sometimes they even help each other succeed. Research<\/a> has, for example, shown that bluegill sunfish \u2014 introduced in the West largely for sportfishing \u2014 can help bullfrogs survive. Sunfish will eat dragonfly larvae that might otherwise prey on bullfrog tadpoles. <\/p>\n

\u201cYou can\u2019t even consider them invasive species anymore,\u201d Garcia said of bullfrogs. \u201cYou have to consider it an invasive community.\u201d <\/p>\n

Bullfrogs are bullies<\/h2>\n

Like unsupervised toddlers, bullfrogs will put pretty much anything in their mouths. Mice, birds, turtles, snakes, rocks, other bullfrogs \u2014 if it fits, they\u2019ll try to eat it. <\/p>\n

This is a big problem for species that are already rare, such as the Chiricahua leopard frog or the northwestern pond turtle. Bullfrogs are shortening their paths to extinction.<\/p>\n

\u201cThey\u2019re implicated in the declines, along with habitat loss and drought, of many of our native reptile and amphibian species,\u201d said Sidney Woodruff, a doctoral researcher at the University of California Davis who studies bullfrogs and other invasive amphibians.  <\/p>\n

In May, Woodruff published a study<\/a> that found that waterbodies in Yosemite National Park that were full of bullfrogs had lower densities of northwestern pond turtles than those without invasive frogs. She also found that where bullfrogs were present, only large turtles could survive. <\/p>\n

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\u201cOur study adds mounting evidence that hatchling and juvenile pond turtle losses to bullfrogs pose a serious threat to pond turtle population persistence,\u201d Woodruff and her co-authors wrote.<\/p>\n

And where bullfrogs live in communities with other invasive species, native animals often face even greater challenges, said JJ Apodaca, executive director of the Amphibian and Reptile Conservancy, a nonprofit environmental group. Non-native crayfish, for example, are voracious consumers of plants and other habitat features that native animals hide in. So, where you have invasive crayfish, the local fauna will be that much easier for bullfrogs to eat. <\/p>\n

Invasive bullfrogs may also be spreading diseases. A study<\/a> published in 2018 linked the arrival of bullfrogs in the West with the spread of a pathogen called chytrid fungus. While the pathogen typically doesn\u2019t sicken bullfrogs, it has helped drive the decline and extinction of more than 200 amphibian species globally, including those in the West. <\/p>\n

Okay, so let\u2019s kill all the bullfrogs? <\/h2>\n

No, a bullfrog-killing spree won\u2019t fix ecosystems in the West. They\u2019re already everywhere, so even if scientists manage to eliminate them from a pond or 10 ponds \u2014 which often requires fully drying out the water body and hours and hours of effort \u2014 they\u2019ll likely come back.<\/p>\n

\u201cIt\u2019s futile,\u201d Garcia said. \u201cWe\u2019re not getting rid of bullfrogs. Not really.\u201d <\/p>\n

Even if we could remove bullfrogs from large areas in the West, ecosystems wouldn\u2019t suddenly revert back to some sort of natural state. Bullfrogs are both a problem themselves and a symptom of change \u2014 of the large-scale transformation of land in the West. <\/p>\n

\u201cThere\u2019s kind of an irony,\u201d said Brendon Larson, a researcher and invasive species expert at the University of Waterloo. \u201cWe’re nurturing these agricultural systems \u2014 which are monocultures and non-native species \u2014 and then we’re turning around and saying we\u2019re surprised when a non-native species does well in response to that.\u201d<\/p>\n

Doing nothing isn\u2019t a great option either. Left alone, bullfrogs will continue to replace native species that comprise the ecosystems we depend on, including insects that pollinate our crops<\/a> and salamanders that can help<\/a> limit the amount of carbon dioxide entering the atmosphere and accelerating climate change. <\/p>\n

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The best approach, researchers told me, is to prioritize bullfrog control \u2014 to get rid of frogs in areas with endangered species or where conservation scientists are reintroducing native species that disappeared.<\/p>\n

This works. For her study on pond turtles earlier this year, Woodruff and her colleagues caught more than 16,000 bullfrogs across two waterbodies in Yosemite \u2014 using nets, spears, air rifles, and other methods \u2014 which they then euthanized. It was only after her team shrank the invasive frog population that they detected small, baby pond turtles in those areas. That suggests that, absent bullfrogs, the turtles were finally able to breed and survive, \u201cproviding some hope for turtle population recovery once bullfrog predation pressures are alleviated,\u201d the researchers wrote. <\/p>\n

Woodruff says she noticed all kinds of other native animals return after clearing out the invasive bullfrogs, including native frogs, salamanders, and snakes. \u201cThe coolest thing to me was that the soundscape changed,\u201d she told me. \u201cOver time, you actually started to hear our native chorus frogs again.\u201d<\/p>\n

Managing bullfrogs is complicated, Woodruff says, and especially for her. She grew up in Alabama and Georgia, where the animals are native. She liked hearing them. But now she lives in California, where she\u2019s studying how they harm the environment, and so hearing them makes her tense up.<\/p>\n

\u201cIt sucks because I love these frogs,\u201d Woodruff said. \u201cIt is not the animals’ fault. They are doing what they instinctively want to do \u2014 survive and procreate.\u201d She tries to stay focused on the point, she said: \u201cWe\u2019re doing this for the native species.\u201d<\/p>\n","protected":false},"excerpt":{"rendered":"

On summer evenings in the Midwest, the muggy air comes alive with a chorus of crickets, cicadas, and frogs \u2014 especially bullfrogs. Their booming mating calls sound like something between a foghorn and a didgeridoo.  As far as we know, summer here has always sounded like this. Bullfrogs are native to most of the Eastern…<\/p>\n","protected":false},"author":1,"featured_media":937,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[14],"tags":[],"class_list":["post-935","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-climate"],"_links":{"self":[{"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/posts\/935","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/comments?post=935"}],"version-history":[{"count":3,"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/posts\/935\/revisions"}],"predecessor-version":[{"id":943,"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/posts\/935\/revisions\/943"}],"wp:featuredmedia":[{"embeddable":true,"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/media\/937"}],"wp:attachment":[{"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/media?parent=935"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/categories?post=935"},{"taxonomy":"post_tag","embeddable":true,"href":"http:\/\/audiomateria.com\/index.php\/wp-json\/wp\/v2\/tags?post=935"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}