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Curious Nature: Leap Day is for the toads

Aspen Dobbins
Walking Mountains Science Center
A boreal toad hangs out on the Ossagon Trail in California's Redwood State Park. Today, boreal toads are estimated to occupy just 1% of their historical breeding areas throughout the West.
Special to the Daily

Hoppy Leap Day! Occurring once every four years, a leap year is almost as rare as this week’s leap loving star. Who might that be, you ask? Warty skin, isolated environments, enjoys the occasional insect … no, it’s not your teenager, it’s actually Colorado’s only alpine amphibian, the boreal toad.

Once abundant across beaver ponds, marshes, and subalpine lakes, these toads have experienced a dramatic population decline that landed them on the endangered species list for Colorado in 1993. So what has caused such an intense plummet in population? Surely the little guys didn’t just hop away.

Amphibians have existed on earth for over 300 million years, but in the past two decades, the slippery critters have been in some pretty big trouble. Nearly 168 species have gone extinct and at least 43% of existing species have populations that are declining. This is detrimental for not only the boreal toad, but all amphibious species.

Other than being good at catching flies, amphibians are good indicators of a healthy ecosystem. Since amphibians live in both land and water environments and have thin skin that they breathe through, they are first to be affected by environmental changes. If there are lots of toads and other amphibians in a habitat, it means the ecosystem is healthy. If these species begin to disappear, it means they are unhoppy with their homes becoming polluted, diseased, and fragmented

Clocking in at a max of 11 centimeters, the boreal toad is one of Colorado’s toughest residents. They survive in alpine environments at elevations from 7,500 feet to 12,000 feet. Boreal toads are gray and greenish in color with dark blotches along their backs and belly. They have a white stripe that runs down their spine as well. One characteristic that really sets the boreal toad apart from other toads is their lack of vocal sac. This gives them a soft chirp instead of that classic loud mating call, or so I’ve been toad.

A large portion of the demise of the boreal toad can be contributed to human impacts such as habitat destruction, pollution, and climate change. Perhaps their biggest threat though is the fungus known as batrachochytrium dendrobatidis. Bd causes a disease called chytridiomycosis which is the lead culprit wiping out boreal toads in the Rocky Mountain region. The fungus makes its home in the outside layer of cells on the toad’s skin, causing the skin to thicken. This toadally stops their skin from being able to absorb water and oxygen. Unfortunately, having thick skin is not very helpful when you’re an amphibian.

The fungus is more commonly passed between male boreal toads as they tend to gather together each year. Females are more solitary and may only breed once every one to three years. This means that even if the population is not severely impacted by the fungus, the sex ratio of the population may become skewed beyond normal, healthy ranges, creating a whole new set of problems.

Today, boreal toads are estimated to occupy just 1% of their historical breeding areas. Conservation efforts have been in place since 1993, including efforts to gain Endangered Species Act protection. However, that protection has been denied every time. Thankfully different agencies, like Colorado Parks and Wildlife, have devoted significant resources in the past two decades toward researching the cause of boreal toad declines in the state and exploring ways to recover the species. Hopefully, these conservation efforts will continue in the future or the boreal toad may finally croak.

This Leap Day, pledge to protect your nearby wetlands and water to help prevent the boreal toad from croaking its last croak.

Aspen Dobbins is a Naturalist at Walking Mountains Science Center who enjoys the occasional insect and searching for amphibians.


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