If you’ve lived in the United States long enough, chances are that you’ve been greeted by hopping, warty friends on rainy days during warmer months
If you’ve lived in the United States long enough, chances are that you’ve been greeted by hopping, warty friends on rainy days during warmer months. Each region of the US is home to a wide array of native amphibians and reptiles, so that toad could be a Western toad, Woodhouse toad, Fowler’s toad, or even a toad species brought back from extinction like the Wyoming toad.
However, it’s Anaxyrus americanus, the American toad, which remains the most well-known toad species even though it isn’t found in the western halves of Canada and the United States. The bumpy bufonid is frequently depicted in art and nature documentaries with reverence as a common garden helper, but the humble American toad has some surprising twists and turns in its natural history.
Was the American Toad Always Endemic to North America?
Researchers from the University of Texas hypothesized that the American toad isn’t actually endemic to North America. Rather, these toads were introduced from South America prior to the formation of the Isthmus of Darien. Known today as the Darien Gap which separates the two continents, but several million years ago, they were much closer in land mass.
The American toad is not found throughout North America. Photo by Joe McDonald/Shutterstock
This hypothesis was based on DNA sequence data from 82 toads in 56 different toad species, and they found that the Nearctic toads were monophyletic. This means that the toads which now live north of tropical Mexico essentially came from the same ancestors. Even though American toads live in colder and more deciduous climates than their South American counterparts like the cane toad and Rococo toad, they have similar neotropical origins with genetic data to back it up.
As temperatures and UV radiation levels rise out west, toad species native to regions west of the Rockies like the Yosemite toad (Anaxyrus canorus) have attained Vulnerable status from the International Union for Conservation of Nature (IUCN) while the American toad’s adaptability and predilection for moister climates keeps it at Least Concern status. While the American toad’s neotropical ancestry would cause it to gravitate to warmer weather, the high humidity below the Equator would explain why these toads took up residence throughout the East Coast given its infamously humid summers.
Adaptations, Evolutions and Threats
The American toad evolved to survive all types of climate conditions, albeit with some limits. The western half of the US is comprised of deserts, rocky mountains, and the Dust Bowl, which tends to lack the moisture that American toads need to thrive despite having stronger resistance to dehydration than frogs.
American toad’s parotid glands. Photo by Jacques Durocher
In a country as large and biodiverse as the US, endemic and introduced toads are always going to find ways to evolve since they have to constantly watch for natural and man made threats. When Wisconsin-based naturalist Charles Long observed giant American toads in the wild, he noted that toads from the Lake Michigan islands were 20-30 percent larger than the toads he captured from mainland Wisconsin. Even more interestingly, Long also observed that these larger island toads moved primarily by walking instead of hopping like their mainland counterparts.
It would make sense that the island-dwelling toads encountered fewer predators and had better access to food than the toads on the mainland, giving them the chance to grow bigger. Although toads generally walk more than frogs do to get around, this difference in movement could be an evolutionary response more than a simple adaptation to avoiding aerial predators. The mainland toads were more likely to encounter land-based predators, where hopping away is a more effective escape route than burrowing under a rock where that land-dwelling snake can easily find a toad snack. Even if a bird of prey spies a toad from several hundred feet above ground, walking away from the sounds of a descending hawk and into a dirt sanctuary buys more time than trying to hop away from a more immediate threat.
Hognose snakes (Heterodon sp.) love to eat toads, as do other species of snakes, but the most imminent threat to the American toad is human activity. Habitat loss from deforestation and high levels of pollution, plus a chytrid fungus epidemic, now pose more significant threats to the American toad than its natural predators.
The hognose snake in the wild feeds largely on toads. Photo by skifbook/Shutterstock
The US Geological Survey found that US amphibian populations decline about 3.79 percent a year, with the declines more pronounced in drought-stricken areas west of the Rockies. As the northeast sees hotter temperatures and the west coast trades its fires for the east coast’s hurricanes, even hardy and adaptable amphibians that have survived and evolved for thousands of years like Anaxyrus americanus comprise an upsetting portion of this decline.
The American toad may continue to evolve in the face of existential threats, as has been seen with other bufonids like the common European toad (Bufo bufo). Scientists across the pond found that adult toads which grew up in human-created habitats like gardens increased their protective chemical defenses in the form of larger parotid glands.
American Toads as Pets
Even though American toads aren’t as endangered as other toad species, it’s not prudent to take one from the wild if you want a pet toad. (The only exception to this might be plucking a cane toad from areas where they are invasive.) However, many people are now winding up with accidental pet toads as they hitch rides on produce that travels a long distance, and it wouldn’t be responsible to release a non-native toad into the wild.
Yael in his water bowl. A water bowl is imperative to ensure the health of this species. Photo by Rachel Presser
As American toads seek shelter from habitat loss and decide they like your home, or wound up a long way from their origins because your peppers got a better vacation than you did, you just might be blessed with a new amphibian friend. While having a pet toad is an incredible experience, a captive-bred pet toad is the way to go if your American toad didn’t cross your path by chance like this.
While American toads are fairly adaptive and hardy, they still need the proper habitat to have a happy and healthy life. The enclosure should be 20 gallons at minimum for one toad, but 30 to 50 gallons is ideal if you want to create the ultimate toad experience.
American toads are usually loners, but they can do well with a friend or two providing that they’re all females or one male to two females. Male toads living together tend to fight. The larger enclosures are what you need if you plan to house multiple toads together. The enclosure should have hides and other toad-friendly enrichment like cork bark and fake plants.
Yael sits on his feeding bowl. Photo by Rachel Presser
Your enclosure should be fitted with a screen top for ventilation, with the type that has doors that open in the front being ideal. The American toad loves to burrow, so you should have at least two to three inches of moist substrate. Coconut fiber works great as does a mix of organic dirt, frog moss, and other non-particulate substrate. Changing the substrate once a month prevents parasites, irritations, and other amphibian maladies.
Temperature and humidity aren’t very complex. Keeping your toad’s habitat at 65 to 70 degrees Fahrenheit (18.3 to 23.9 degrees Celsius), or about room temperature, is ideal. An under-tank heat pad should be under one side of the glass tank so that it provides a heat gradient, giving your toad a place to warm up on cold days and a cool side to hide when it gets hot. Mist at least twice a day or install an auto-mister, as misty substrate equates to happy toads.
Essentials to Consider for Your American Toad
Mist King V 5.0 Starter Misting System
Zoo Med ReptiTherm Under Tank Heater
Zoo Med Reptivite with D3 Reptile Vitamin, 2-oz bottle
Rep-Cal Calcium with Vitamin D3
Zoo Med ReptiTemp Digital Reptile Terrarium Thermostat
Zoo Med Forest Floor Natural Cypress Mulch Reptile Bedding
Exo Terra Infrared Reptile Thermometer
A humidity gauge in the tank can tell you if you’ve achieved at least 50 percent humidity, a good baseline for American toads. They also don’t require special UVB lighting like reptiles do.
These toads don’t need water features because they spend more time on land, but they still need a water dish. Get a shallow dish, preferably a ramp bowl they can easily climb in and out of. The water should be changed daily and bottled water is safer to use than tap water or distilled water.
Relaxing. That’s Yael. Photo by Rachel Presser.
American toads eat all kinds of bugs in the wild like slugs, worms, crickets, beetles, and other garden pests. They like readily-available feeder bugs like crickets, waxworms, superworms, beetles, and dubia roaches. Because pet toads don’t need to hunt as much as wild toads, you only need to give them three to five medium-sized bugs per feeding. Adult toads only need to eat two or three days a week, juvenile toads should be fed daily.
Dusting the bugs with a calcium supplement and vitamins keeps your toad healthy. While you can form a bond with your American toad, you need to keep handling at a minimum and do so safely. Toad skin is incredibly porous, so you need to wash your hands both before and after handling. Wearing gloves also ensures safe toad handling.
Sources
1 https://onlinelibrary.wiley.com/doi/10.1111/j.0014-3820.2004.tb00881.x
Pauly, G. B.; Hillis, D. M.; Cannatella, D. C. (November 2004). “The History of a Nearctic Colonization: Molecular Phylogenetics and Biogeography of the Nearctic Toads (Bufo)”
2 https://www.fs.usda.gov/nrs/pubs/jrnl/2022/nrs_2022_brown-d_001.pdf
The American Toad, Natural History Box
3 https://www.usgs.gov/faqs/why-are-amphibian-populations-declining
4 https://www.nature.com/articles/s41598-019-39587-3
