“There’s one Mom!” My son drops down beside a small frog perched on a reed. Sensing his presence, the frog leaps further down the bank. My son is a blur of bright yellow rubber boots and unfettered enthusiasm as he runs alongside, hoping for a better look. Water sprays and the frog jumps around effortlessly, until finally it settles in a small pool. “Over here!” he yells, motioning me to him. We crouch around it, two giants hovering like low clouds over this tiny creature. It’s a Columbia spotted frog, its back a dark moss green and speckled with small irregular dark brown spots. For the next few moments, we marvel over its tiny webbed feet, beefy quadriceps and bulging eyes. 

I remember going to the same spot at Cottonwood Slough with my Dad. Frog watching is one of the first encounters many of us have with wilderness. There is something other-worldly about them, as if when close to one, you’ve been let in on a secret. I am saddened then, to read that frogs, and many amphibians (toads, salamanders and newts) around the world, are succumbing to what one review calls “the largest infectious disease threat to [their] biodiversity,” the spread if chytrid fungus. 

Chytrid Fungus causes a disease in amphibians called chytridiomycosis. This disease is responsible for widespread amphibian decline. Several studies document over 200 species’ extinctions on six continents. It’s been difficult to determine a trend in amphibian decline due to a lack of long term monitoring over several decades. Declines in some Alberta amphibian populations have been noted, which are likely due to habitat loss. 

The fungus is thought to kill host amphibians in a couple of ways. Primarily, it targets keratin, a fibrous protein that toughens their skin and helps regulate the water content of their bodies. In tadpoles, it affects the development of mouthparts, disrupting their ability to take in food and thrive. In juveniles and adults, it is thought to disrupt processes critical in maintaining the life of cells and removing metabolic waste from the body.

The fungus was first reported in wild and captive frogs in North and South America and Australia. Ecologists are not sure whether the fungus naturally occurs here in North America, or whether it was brought here from somewhere else. One theory suggests the fungus traveled between continents by the trade of infected frogs used for human pregnancy tests, and more recently in the trade of American bullfrogs most commonly served as “frog legs” in restaurants. Regardless, we know it can spread from site to site, although the mechanisms aren’t well understood. Frogs may carry the fungus when they disperse across the landscape. It may also be transported by birds, humans, and insects. I was recently given a tour of the veterinary hospital at the San Diego Zoo and Wild Animal Park. Several of the exotic amphibians in their care had been infected with chytrid fungus, and one veterinarian hypothesized the fungus may have come in on the hands of volunteers who have amphibians at home. 

In addition to being spread by contact, ecologists have not ruled out the possibility the fungus may have an environmentally resistant stage that allows it to be spread by wind.

According to Scott Stevens, a species at risk biologist for Sustainable Resource Development, the fungus is widely distributed in the province, and its presence here is not new. It has been documented in museum frog specimens as early as 1973, although the monitoring of live species is relatively recent. Although it is devastating some populations in other parts of North American like the Colorado Rockies, Stevens says as of yet, there have been no scientific links established between the presence of Chytrid Fungus in Alberta and local amphibian population declines. 

Part of the reason for this may be that not all frogs that carry chytrid fungus develop the symptoms of the disease chytridiomycosis. It is possible some species are more susceptible than others. It is also possible that human-caused or environmental factors have put some populations more at risk. For example, frogs that are already stressed by water pollution, lack of habitat or climate change, maybe be more susceptible than those that are not.

Ward Hughson, Aquatic Specialist for Jasper National Park points to the importance of monitoring in understanding the level of threat chytrid may pose. “The point of monitoring is to be aware of change when it happens.” 

This means conducting surveys over a number of years. Like other ecologists in the province, Hughson is monitoring for the presence of chytrid fungus in live populations here in Jasper National Park. Frogs and toads are briefly captured and their skin is swabbed. Swabs are sent away to a lab to be cultured. Monitoring began last year, and Jasper is still waiting for the results. Stevens says the appearance of chytrid in Jasper is not inevitable, but likely. 

A lack of scientific evidence linking chytrid fungus to amphibian decline in Alberta does not mean there has been no impact, or that we will not see one in the future. It simply means we don’t know either way. With no long-term baseline data, population changes can be difficult to detect. Examples of previously unexplained amphibian declines now linked to chytrid fungus are beginning to emerge. An eleven-year study in Colorado now links the fungus to a population decline of boreal toads. Here in Alberta, it may be years before ecologists understand the level of threat chytrid poses to local populations. 

In the meantime, Stevens says the best thing the public can do to prevent the spread of chytrid is to reduce or eliminate the transfer of aquatic plants and animals between sites. This can be done by keeping boats, boots and equipment clean.

Back at Cottonwood Slough, my son and I watch the Columbia spotted frog swim to the edge of the small pool, then climb onto a rock to sun itself. Suddenly, a small fly whizzes by, and the frog’s long tongue picks it out of the air in less than a second. “Whoaahh” we both scream. What timing. For us, the magical world of frogs is very much alive, for now.