Last summer, Kansas State University veterinarian Gretel Tovar-Lopez headed south on Interstate 35 bound for Oklahoma State University, home to a colony of Sonoran desert toads. She and her colleagues wanted to give each toad a neurological exam to find out whether what’s normal in one species is normal in another.
It turns out it’s not. In fact, clinicians know little about what’s neurologically normal for toads, given scant research into the matter.
So why does it matter what’s normal for a toad?
For one, toads — a type of frog — play a critical role in the food chain, keeping insects in check and becoming food themselves for snakes, birds and mammals. Second, their health reflects the health of the planet. Shrinking numbers can be early warning signs of climate change, environmental pollution or disease.
When the monsoon gets underway in Tucson, reactions are mixed. Toad fans jump at the chance to delight in the desert species’ chunky bodies and distinct sound, described as a low-pitched trill. Others fear the toxin-coated toads on behalf of their dogs.
Some people exploit the toxin for hallucinogenic effects by either licking a toad or drying and smoking the substance. On social media in 2022, The National Park Service advised people to “refrain from licking” toads.
“Licking toads is a dangerous prospect for humans and pets,” according to Robert Villa, community outreach assistant at the University of Arizona’s Desert Laboratory on Tumamoc Hill. It can be dangerous for toads, too, leading to poaching, over harvesting and displacement.
The lack of research doesn’t just affect wild toads. It shapes how veterinarians examine people’s pets as well, starting with the basics of what a toad checkup involves.
A checkup begins with getting its history, including how long it’s lived with someone, where it’s from, what it’s fed, how it’s housed and how long it’s had any symptoms.
Arizona-Sonora Desert Museum, with a resident Sonoran desert toad. Credit: Robin Tricoles
“We actually have a checklist for the owner to fill out, like when you go to the doctor,” said Greg Lewbart, professor of aquatic, wildlife and zoological medicine at North Carolina State University. “Then we do a physical exam from nose to butt.”
Although toads can go weeks without food, anorexia is a sign a toad is unwell, especially if the toad looks weak, lethargic or has lesions. In such cases, a checkup is warranted.
“I have a special place in my heart for marine toads,” said Lewbart. “They’re sturdy.”
As was Worm Man, a Budgett’s frog that Lewbart looked after for 17 years until Worm Man succumbed to cancer. A group of elementary school students named him for his enthusiasm for dining on worms.
Krista Keller, a zoological veterinarian at the University of California at Davis, said most of the patients she sees have human caregivers, but she also works with zoos to manage their collections. “Zoos and aquaria are where the majority of frog and toad medicine happens,” she said. “But I also have clients who have beloved frog and toad family members, especially because toads tend to live a lot longer.” Sometimes as long as 30 or 40 years.
Because their skin is semi-permeable, veterinarians must handle them with care. “We always have to make sure that we are wearing gloves,” said Keller. “Not just to protect us from anything that they might be carrying on their skin, but truly to protect our patients.”
Toads are placed in an open Ziplock bag with a little bottled water to keep it from hopping around and hurting itself, then they get a close look at its eyes, mouth and body condition.“Are they too fat? Are they too skinny? We’re looking at their ability to hop or move around and at their strength,” Keller said.
Veterinarians also check a toad’s heartbeat with a Doppler monitor, the same technology used to hear a fetus’s heartbeat.
“Even more fun than that is a technique called transillumination,” said Keller. “Some of my frog and toad patients are very small, and because they’re so small, you can shine a bright light behind them and see their organs.”
Neurological exams like the ones Tovar-Lopez is conducting are a different story.
Learning what’s neurologically normal helps clinicians determine whether an illness is caused by disease or trauma. For example, fungi infections can lead to limb weakness or immobility, but so can physical trauma.
“We didn’t know what was normal and what was abnormal, so we started developing testing for all of the healthy animals and developing something that was appropriate for each species,” said Tovar-Lopez, who works with zoo species and wildlife.
The neurologic exam is the same across all species. “What changes is how they respond to different tests,” she said.
For example, Tovar-Lopez has found that Puerto Rican crested toads display a withdrawal reflex when gentle pressure is applied to their foot, but Sonoran desert toads do not.
“I honestly didn’t think that I was going to find a difference between these two species that are so related,” she said. “It was surprising.”
Something else surprised Tovar-Lopez. Each toad displayed its own personality during the exam.
“Some of them were like, just stop it, or let me take a break, and other ones would be like, well, I don’t care. Just do whatever.”
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