By Ryan M. Connor
Going to sleep was always a struggle at my grandparent’s house on the humid South African coast when I was growing up. It wasn’t the bright moonlight or the snoring that kept me up at night, it was the screeching croaks coming from right outside my bedroom near the pool. It was annoying, but my passion for nature didn’t mind it so much as it did the others in the household. You too may have had those sorts of experiences when it came to frogs in your past.
One of the most recent adventures I went on was down to Denver, Colorado. I went to a reptile convention with a few friends from college. There were reptiles and amphibians filling the conventions floor. Many, creatures I had only ever seen pictures of. I got to thinking why I had only ever seen these animals in pictures, when they were everywhere when I was a child. It turns out that I wasn’t alone in thinking this.
“One of the more larger experiences in my life was of my great grandmother, who used to live by a large pond and a lake and we used to look for tadpoles and that was really a large moment [in my life],” said Erika Stonebay, an invested amphibian pet owner from Fort Collins, Colorado, who has been keeping frogs for about 14 years. With wide eyes she exclaimed, “Eventually that frog pond became a pond without frogs.”
The United States Geological Survey (USGS), found:
“The average decline in overall amphibian populations is 3.79 percent per year, though the decline rate is more severe in some regions of the U.S., such as the West Coast and the Rocky Mountains. If this rate remains unchanged, some species will disappear from half of the habitats they occupy in about 20 years.”
The sad part is, these effects are being seen worldwide. Which explains why my family hasn’t seen or heard many frogs in South Africa for so long.
One of the biggest reasons for this decline is because of Batrachochytrium dendrobatidis (Bd), better known as the chytrid fungus which causes chytridiomycosis in amphibians. It has caused the decline of at least 501 amphibian species worldwide, including 90 species to have gone extinct because of it, according to Matthew Warren from Journal Nature.
Amphibian skin is like a lung, they use their skin to breathe, but to do this the skin must be moist, just like our lungs. Its why amphibians live near water, to keep moist.
“The fungus has little tiny microscopic swimming zoospore stages that swim up, attach to their skin and go inside their skin cells,” explained Dr. Valerie McKenzie, a professor at University of Colorado in the department of Ecology and Evolutionary Biology who studies parasites and pathogens of amphibians, including the Chytrid fungus.
Dr. McKenzie elaborated on the issue, “Imagine for example, there were one virus that was wiping out [animals] across the mammal diversity. What if COVID didn’t only affect people, but also was killing bats, rats, dogs, cats, donkeys, whales? If COVID was killing all those mammals all at once, we would be in full panic, freaking out. That’s what’s happening to amphibians with this fungus.”
Amphibians act as middle players in the ecosystems. They themselves are food and they are predators, eating tons of insects constantly. She said, “If you took amphibians away from our environment, you could see a big increase in insects.” This is worrying considering that insects can be crop pests, and that insects include mosquitoes which carry and transmit diseases to humans. Amphibians keep these populations under control.
Dr. McKenzie pointed out how amphibians are food for many other larger vertebrate organisms too, so declining amphibians populations will have an “up-chain” effect on those animals. “So, they’re an important puzzle player in the food webs of our ecosystem,” Dr. McKenzie explained.
And Chytrid Fungus is not the only thing plaguing amphibian populations. Climate change and land use changes do too.
Climate Change
Changes in temperature can lead to changes in the timing of life processes such as hibernation, and create mismatches with food webs and exacerbate amphibian species vulnerability, according to Gao et al. (2015).
Erika Stonebay, who is also studying Zoology at Colorado State University explained that amphibians respond to changes in the environment in different ways and some frogs can be more tolerant to climate changes like freezing for example. But she explained that some of these extreme changes in the climate, mean that the frogs are unable to go through the processes that they need in time in order to get to move on with their life, and thus survive.
“It’s making it harder to get a hold of certain species of frogs or they’ve gone entirely extinct in the wild. So now you can only get them from captive bred, which has also inflated the prices. Which, isn't the point but it is sad,” she said. It impacts her and other pet owners who care about the conservation of these animals. Stonebay explained, “I have Firebelly toads and it’s usually recommended that you have a group of three, but I only have two and I cannot get any more, so it affects their behaviors.”
Stonebay advocates for not going out into the wild and decreasing amphibian populations there, explaining the importance to not spread chytrid fungus and other parasites into captive populations because she says, “Once it is in the population, its very difficult if not impossible to get it out of that population.” That is why she says “there should be a barrier between wildlife and captivity because if some of these parasites and chytrid fungus do get introduced to the captive populations, then [amphibian species] will be gone.”
Land-use changes
Land-use changes have also exacerbated much of the issues related to climate change and the chytrid fungus. Dr. McKenzie said, “The way [chytrid fungus] affects [a] species or population does vary, there are some species that are heavily affected and die a lot, like boreal toads. And there are other species that can handle these [effects] and be okay with it,” she explained. Colorado has both types, and the frogs that are okay with the fungus act like “Bd farms,” exposing the susceptible species to the fungus.
The species that are okay with it are invasive bull frogs, which are not native to Colorado. She said that they're becoming “really abundant, especially up and down the front range where there is modified habitat a lot.” Bullfrogs require permanent water bodies, which are not naturally abundant in Colorado. She said, “If there are ponds in Colorado they tend to be ephemeral, where they dry up in the late summer.” She explained that human communities have created a lot of unnatural permanent bodies of water, like storm runoff retention ponds and golf course hazard ponds. And these are good invasive bullfrog habitats.
Can we help?
As much as all the problems sound hopeless, there have been a lot of work to try and find remedy to the issues. For example, some chemicals released by some amphibian cells act as a “kryptonite to the fungus,” Dr. McKenzie said. “I started wondering, Wow, I wonder if any of those bacteria live on boreal toads here in Colorado. And so I started looking and we[(Dr. McKenzie's lab)] found some,” she said. Her labs experiments have been focused on learning about the symbiotic bacteria and whether they could manipulate them to make a treatment to make amphibians better able to tolerate the fungal disease. She said, “We’ve had success doing it in lab experiments.” She went on to say how a graduate student finishing his PhD is now leading trials to test this treatment in the wild.
How this treatment works is by releasing trace antifungals that can help repel chytrid fungus spores. She explained how the probiotic treatment will prevent most of the spores from getting to skin cells and infecting the frog, but she explained, “some spaces might have lots of those chemicals blocking those spores, but then other patches of the skin might have less, where some of those spores can get in, so it’s not going to prevent total infection, but it can reduce the level of infection quite significantly.”
A new variant of the chytrid fungus has also recently become known called Bsal according to USGS (2018). Which has begun threatening salamanders. A single Bsal spore is lethal, whereas around 10,000 were lethal for Bd. Spillover from captive to wild populations is the suspect for the introduction of the fungus into Europe. It is a major concern to the United States, and has even prompted the creation of a Bsal task force to deal with the issue. Unrestricted and unauthorized translocation, importation, propagation are what is leading to many of these issues, and these are issues agencies like Colorado’s Division of Wildlife (2001) try to regulate. But it requires current and future amphibian pet owners to be responsible to stop detrimental problems like chytridiomycosis from becoming widespread more than it already is. It requires people to advocate for research and procedures to be put in place to prevent outbreaks such as Bd and Bsal.
Dr. McKenzie said, “We as humans are the cause of what is being called the sixth mass extinction event.” Elaborating she said, “Sometimes, it’s obvious that we’re destroying habitat or overfishing. But one of these ways that’s more insidious and we don’t realize we’re doing it, is by accidentally spreading wildlife diseases around the planet.”
There’s there’s a lot more in Pandora’s box that we can prevent if we get better about our biosecurity and if we are much more careful with the way we move things around the globe; we can still have a globalized, successful, modern world, but we can be way more careful in how we move things around and not pass these pathogens. ~Dr. Valerie McKenzie (PhD)
There is a common misconception with amphibians that their kind of slimy and dirty, but their benefits to humanity are immense. And for Stonebay, whose primary love in animals stems from frogs, she feels hurt by this attitude towards these animals, whose diversity rivals that of mammals, and whose diversity is more threatened than mammals, reptiles, bird, and fish.
Stonebay says, “I really do advocate for keeping these animals in captivity because then we’re not going as much out into the wild and decreasing their populations there and bringing in potentially dangerous parasites and diseases.”
~1,791 words
Ryan M. Connor
