Common Toads Aren't So Common Anymore

Christian Fischer via Wikimedia Commons // CC BY-SA 3.0
Christian Fischer via Wikimedia Commons // CC BY-SA 3.0 / Christian Fischer via Wikimedia Commons // CC BY-SA 3.0

If the global decline of honeybees has taught us anything, it’s that even the most commonplace, ordinary species are vulnerable. Researchers working with the “Toads on Roads” project now report that populations of common toads are shrinking in the UK and Switzerland. They published their findings today in the journal PLOS One.

The common toad (Bufo bufo) may look rugged, but it’s actually quite fussy about certain things. Mating, for instance—they only want to do it in the ponds where they were born. This typically necessitates a mass migration from their adult territories. Like crabby toddlers, the toads require routine. They’ll follow the same paths back to the pond year after year, hopping around new housing developments and across roads if they have to.

This does not always go well for them—but they’re not totally alone. Volunteer corps of amphibian sympathizers have existed since the 1950s, forming patrols by the side of busy motorways to carry warty would-be lovers to safety. One group, Froglife, has been running its “Toads on Roads” program for more than two decades, helping tens of thousands of amphibians each year. 

It’s an incredible volunteer network. And if you’re a herpetologist, it’s also a pretty excellent source of population data. All you have to do is organize survey nights and hand out plastic buckets.

The researchers behind the current study pulled toad migration statistics from Froglife and other pro-toad volunteer groups from 1975 to 2014 in the UK and from 1973 to 2012 in Switzerland. They knew that most of the toads caught and recorded would represent just part of the whole population—namely, the adults—and used those numbers and what they knew about toad life cycles to estimate how large each population was. They looked at 153 populations in the UK and 141 populations in Switzerland.

The numbers were not encouraging: Researchers found that since the 1980s, toad numbers in both countries have gone down quickly and continuously. Within a few years, if these trends continue, the so-called "common toad" could qualify for the International Union for the Conservation of Nature (IUCN)’s Red List, which identifies species on the brink.

“The fact that toad abundance significantly declined across both countries since the 1980s even at sites where there was an obvious and long-term conservation action in place, (i.e. moving individual toads across the roads by volunteers) is troubling,” the authors write.

The precise causes of the toads’ decline are not completely clear, although the scientists did find a thoroughly unsurprising relationship between urbanization and toad population decline. Traffic and automobile density have greatly increased in both countries over the last 30-plus years; in the UK alone, they've doubled. The toads are also up against some very familiar issues: habitat loss, disease, and climate change.

“While significant conservation improvements have recently been achieved for some endangered species,” the authors conclude, “common species, including amphibians, are still rapidly declining in Europe, largely unnoticed due to lack of resources for monitoring and despite the fact that such species have a disproportionate impact in providing ecosystem function and structure.”

Want to roll up your sleeves and get in on the toad-saving action? If you live in the UK, visit the Froglife website and look for a toad patrol near you. Live elsewhere? Check out your local wildlife center or conservation organization and see if they need help.

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