Native Aquatic Species Coordinator Harry Crockett with Colorado Parks and Wildlife (CPW) answers some of our questions about how Denver Zoo got involved with boreal toads in Colorado, and how YOU can help save wildlife in our state. 

Denver Zoo: What inspired you to work for CPW? 

Harry Crockett: I always wanted to be a wildlife biologist, and always leaned toward things that live in the water, owing to a lifetime of fishing, working a number of seasons as a river trip guide, and other water-oriented passions. When I got my Masters at Colorado State University, my thesis project was in cooperation with Colorado Parks and Wildlife, so I got familiar enough with the agency to know I wanted to be part of it. I was lucky enough to get hired by CPW as a seasonal technician which made me even more sure of my career path. Working with the boreal toads has become one of the most compelling parts of my job.  

DZ: Why are boreal toads an important species to work on restoring in Colorado? 

HC: Aldo Leopold’s famous ecological insight that the first rule of intelligent tinkering is to keep all the parts, certainly applies to these toads–we don’t fully know the role they play in the montane environment but we know they have a role and it’s important. For those who need a more human-utilitarian reason to care about boreal toads, all amphibians are important indicators of aquatic and riparian system health because they are so much a part of both the aquatic and terrestrial worlds. They’re an early warning system about water quality and overall environmental health. Toads used to be very common throughout the Southern Rockies–there are many anecdotes from the 1960s and earlier of them being so abundant around montane wetlands at certain times of the year that one had to work to avoid stepping on them. And the fact that they have declined so greatly shows that something is badly amiss–an invasive disease in this case.  

On a basic level of connecting with another species, you don’t maybe think of toads as charismatic but boreal toads have a ton of personality. Interacting with them will definitely deepen your appreciation that even humble species are inherently important. I want my grandkids and all future generations to be able to go up in the mountains and encounter toads in their natural habitat, it’s part of the full experience of the greatness that is the Southern Rocky Mountains. 

DZ: How did Denver Zoo come to work with CPW on the boreal toad project? 

HC: The interest really started on the Denver Zoo side, going back more than 10 years, before I was even involved. Zoo staff would attend the Boreal Toad Conservation Team meetings every year, and we just kept up discussions about how we could increase our collaboration. For the past few years, the Zoo has housed and bred boreal toads for release in Utah, so we were very intrigued with that possibility for our toads from the Southern Rocky Mountain populations. When the greater space resources became available, CPW and the Zoo both jumped at the opportunity.    

DZ: What makes Denver Zoo uniquely qualified to be a partner in this project? 

The specific success at breeding boreal toads in captivity, that I mentioned above, was very compelling because that’s proven to be really hard to do. We had a lot of luck earlier on at the Mumma Native Aquatic Species Restoration Facility (CPW’s native species hatchery, producing 12 species of at-risk fish plus the boreal toad), but it’s been much more hit-and-miss for going on ten years now. The fact the Zoo was producing the same animal for Utah definitely caught our eye. But beyond that, we know the Zoo is a national leader in breeding and assisting in other ways with conservation of imperiled amphibians from around the world. To have such a great resource right here in our own backyard is certainly a unique opportunity.  

DZ: How can people do their part to preserve and protect Colorado’s natural species and spaces? 

HC: For the toads specifically, there are some very practical things you can do to help, and one of the biggest is to avoid behavior that might spread the chytrid fungus to new areas. Staying on trails is great; especially avoiding going from one wet area to another without changing/ drying / disinfection footgear in between. The same precautions will keep you from accidentally stepping on a toad or degrading sensitive wetland habitat. If you’re fishing, disinfect your waders when going from one body of water to another (you should be doing this anyway to avoid spreading whirling disease and other organisms that can imperil sport fisheries).  

More generally, support conservation in whatever way works for you. The Zoo has terrific volunteer and community science programs, and so does CPW.   Getting involved in a way that gets you interacting with a part of nature that you really care about is so much more personally rewarding than just writing a check, although donating money is also important if you can afford it.       

For more information about our boreal toad project click here and follow us on Facebook, Instagram, TikTok and Twitter for updates! 

By: Julie Krajewski, Colorado Conservation Specialist 

High on Mount Evans, visitors can enjoy views of mountain peaks, alpine lakes and glacier valleys, as well as the chance to see iconic Colorado wildlife, such as Rocky Mountain bighorn sheep, mountain goats, pika, and yellow-bellied marmots. The Summit Lake area is a National Natural Landmark and home to rare plants only found at Summit Lake and in the Arctic circle. With the highest paved road in North America providing the opportunity to drive to 14,130 feet, the Mount Evans Recreation Area attracts 200,000 visitors each year.  

While it is unusual to see mountain goats and bighorn sheep in areas with high human activity, on Mount Evans, the sheep and goats often congregate around parking lots and roads. This close proximity to humans can pose serious risks for both tourists and wildlife. Sheep and goats are susceptible to many hazards when near humans, including increased stress, behavioral changes, disease risk, and exposure to human food as well as human and pet waste. Bighorn sheep and mountain goats may act aggressively towards humans if they feel threatened. Both sexes of sheep and goats have prominent horns and are capable of inflicting serious injuries. In 2010, a hiker was killed by a mountain goat in Olympic National Park. 

In 2020, Denver Zoo began to study and address human-wildlife conflict on this iconic fourteener. While the Mount Evans Scenic Byway is typically open during the summer months, it was closed due to COVID during the 2020 season creating an experiment for how the presence/absence of huge crowds of visitors impacts wildlife behavior. With support from a National Geographic grant, DZ scientists used remote cameras to document how wildlife used the landscape while the road was closed.  

This work continued during the summer of 2021, when the road reopened to visitors. Last summer, Denver Zoo’s Field Conservation team began investigating how to discourage wildlife from congregating in high-human use areas. Bighorn sheep and mountain goats seek out sources of salt and other minerals in their environment. In addition to naturally occurring mineral licks, sheep and goats are drawn to human-created sources of minerals. Some examples of these mineral sources are salt on vehicles and roads, and minerals in human urine found at restrooms and other places humans and their pets urinate. We took soil samples at different locations across Mount Evans to look for signs of higher salt content or other pollution. Also in 2021, Denver Zoo scientists experimented with the use of mountain lion urine as a deterrent to discourage bighorn sheep and mountain goats from coming into the parking lot at Summit Lake. With signs of a predator in the area, goats and sheep may be less likely to enter the parking lot and to congregate around human-created mineral sources.  

Aside from interactions with humans, there are other potential dangers to unusually large congregations of bighorn sheep and mountain goats. A higher density of animals in a small area can lead to increased competition for resources and increased aggression within the herds. Larger groups also create the potential for increased disease transmission. The primary threat to bighorn sheep populations today is pneumonia, caused by the bacterium Mycoplasma ovipneumoniae. This bacterium was introduced from domestic sheep herds to wild sheep and goats. While mountain goats typically don’t become ill from Mycoplasma, they can be carriers of the disease and can spread it to bighorn, which are very susceptible and face high mortality rates when infected (70-90%). Large congregations of sheep and goats can create super-spreader events that put entire herds at risk. 

Denver Zoo’s work on Mount Evans continues in 2022 as we collaborate with Denver Mountain Parks, US Forest Service, and Colorado Parks and Wildlife to make Mount Evans a safer place for both visitors and wildlife. Some ways that you can help keep wildlife safe and healthy are to only observe wildlife from a safe distance, back away if bighorn sheep or mountain goats approach you, utilize available restrooms, and practice Leave No Trace principles (pack out what you carry in). And never feed wildlife. Keep an eye out for Denver Zoo staff if you’re on the mountain this summer — we’d love to answer any questions you may have about how to share the land with wildlife! 

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