In the Upper Minnesota River Valley lies a landscape with bedrock estimated as old as 3.6 billion years—land with ancient bones. In places the bones poke up through the thin topsoil to form rock outcrops. These rocky expanses have seen ice, fire, and flood. Their vistas are inspiring and may surprise those unfamiliar with this part of southwestern Minnesota. They entice you to touch and gently explore their hidden spaces and perhaps to see the world from different perspectives.
The prairies of this region—including rock outcrops as well as adjacent grasslands and savannas—once were vast and were maintained by bison, fire, wind, and water. Today, most native prairies have been lost or degraded. Those that remain can host rare and sensitive species particularly adapted to these distinctive habitats. Some of these species are tiny, elusive, or ephemeral—easy to miss or to harm, so one must tread carefully. My story is of two special creatures, common five-lined skinks and bullsnakes, and this valley that is their home.
Looking Out for Reptiles.
I'm part of the Minnesota River Reptile Project Team, a collaboration since 2015 of the DNR's Nongame Wildlife Program and the agency's Minnesota Biological Survey. Our mission is to better conserve Minnesota's reptiles in the Upper Minnesota River Valley. To help do that, we're studying common five-lined skinks and bullsnakes, also known as gophersnakes.
Reptiles are fascinating creatures that play important roles in the food web as both predator and prey. Some, like our project species, are listed as species of greatest conservation need under the Minnesota Wildlife Action Plan. Reptiles are generally far less studied than game species and most birds, resulting in critical information gaps. In this valley, our knowledge of reptile numbers, distribution, habitats, and conservation needs was outdated and sparse. On top of that, conservation and land-use decisions generally haven't considered reptiles. That's a concern because reptiles have distinct needs and can respond differently than other wildlife to habitat changes. Snakes and lizards certainly can't fly to new places when their habitats are lost or no longer suitable.
Natural resource managers, conservation groups, and others concerned about these species are requesting better data and expert guidance about rare reptiles and other underrepresented wildlife in wildlife management areas, state and county parks, scientific and natural areas, and private lands. That's where we come in.
The project team began by identifying potential habitat on public and private lands in the valley, based on previous records and new information. We also asked DNR staff and local residents to report sightings of these elusive reptiles. We then took to the field to find both reptile species, hiking many miles, often over rugged terrain.
In Search of Skinks.
The common five-lined skink is a small, striped lizard that is sometimes nicknamed the "blue devil" for its electric blue tail, most vivid in juveniles. You might think this would make skinks really easy to find. Think again.
Despite the name, they're secretive and, in Minnesota, rare—unlike the much more common northern prairie skink. Finding a five-lined skink requires diligence; catching one takes skill. When we spy one, there's no time to think! Braving prickly pear cactus spines, we fall to our knees and pounce quickly yet gently to capture a wily five-lined skink in cupped hands.
We're not always lucky. This tiny lizard is wicked fast and has a detachable tail, a clever adaptation that can foil both predator and biologist. Even so, we've captured more than 300 five-lined skinks at more than nine locations. We photographed, weighed, measured, and marked each skink before release.
At many sites we documented skink occurrence and distribution. At three key sites, we monitored populations more intensively by checking daily beneath squares of plywood and tin set along survey routes across outcrops and adjacent habitats. We also collected detailed information about these habitats. This allows us to estimate skink abundance and to evaluate how they use habitats and respond to changes, such as invasions of woody plants and land management practices like cutting vegetation, spraying herbicide, and conducting prescribed burns.
This five-lined skink population in western Minnesota is separated from others by geology and distance. Its nearest Minnesota counterpart is nearly 134 miles away, and its habitats actually are more like those of its cousins in southern Ontario than those in southeastern Minnesota.
Throughout most of their range, five-linked skinks are associated with hardwood forests with some openings. In contrast, the population we are studying is found among large outcrops of granite or gneiss that supply open areas for basking. Yet the skinks spend most of their time under cover. Rocks, stumps, logs, crevices, and patches of grasses and forbs provide protection from predators and weather extremes. Skinks also rely on these spots for nesting and hunting for insects, spiders, and other small prey. Adjacent woodlands and scattered trees offer shelter from the summer heat. In our study area, five-lined skink habitats usually include water sources like wetlands or small outcrop pools.
To survive, skink populations need all these things in close proximity since they can't travel far. And there's the catch: Rock outcrops are in limited supply. Furthermore, not all outcrops are equally suitable. Some are skink havens. Others naturally lack critical features like deep crevices where skinks can survive winters.
Unfortunately, many once-inviting sites are no longer "skink friendly" due to habitat loss and degradation. Historically, periodic fires and native grazers helped keep prairie open while maintaining fire-tolerant oak savanna, where bur oaks provide cover. After European settlement, however, fire suppression, periodic drought, and reduced grazing allowed aggressive species like red cedar, sumac, and buckthorn to dominate. Native wildlife and plants especially adapted to open outcrops were crowded out.
Our findings indicate that skinks benefit from selective cutting, prescribed burning, and careful herbicide application to keep invasive species at bay. Monitoring sensitive species like skinks helps us refine how, when, and how often we take these steps and to know which special features to retain or restore such as loose rock, downed decaying logs, woodland edges, or scattered trees. Roads and land development fragment landscapes, and rock quarrying can destroy these irreplaceable resources. When habitat losses mount, travel between remaining habitats becomes risky or impossible for these small animals, further imperiling isolated populations.
Beautiful and Elusive.
Bullsnakes are beautiful! They're typically tawny and golden yellow with distinct dark blotches and bands. Like intricate beading, the bold patterns on their heads uniquely identify each individual. Adults may reach more than 6 feet long, making the bullsnake the longest snake species native to the upper Midwest.
Locating bullsnakes posed an even greater challenge than five-lined skinks. For nearly three years, we attempted to live-trap bullsnakes where they had been found years before, and we searched several other potential sites. Through spring 2017, we had found only one confirmed hatchling bullsnake and empty eggshells from a successful clutch, but no sign of adults. This didn't bode well. Were they nearly gone in southwestern Minnesota?
Then last June—eureka! A private landowner alerted us to bullsnakes on his property. Since then we've captured 12 bullsnakes: eight adults and four juveniles, with a mixture of males and females. As we did with the skinks, we documented and marked each one. With help from a veterinarian, we implanted radio transmitters in 10 snakes to help identify individuals and to track their movements and habitat use. The other two were captured too late in the season to safely implant transmitters.
Snakes in a Squeeze.
Why are bullsnakes so hard to find? Their coloration acts as camouflage, allowing them to blend into surroundings. They also spend a lot of time in burrows seeking cover and prey. More importantly, they're increasingly rare, and so are their key habitats. In eastern Minnesota, bullsnakes tend to be found on dry prairies, savanna, and woodland edges. These areas usually are very sandy and have abundant pocket gophers.
However, many prairies here have since been developed or converted to sand and gravel mines or fields of row crops. Some are slated for off-road vehicle recreation. Others have been engulfed by trees, shrubs, and invasive species.
In this valley, our project team has found bullsnakes in only one locale so far, almost exclusively on grazed pasture. Like fire, moderate grazing helps stem the tide of woody invaders, although bullsnakes mostly avoided heavily grazed areas. The hillsides where we found the snakes were only slightly sandy with few native prairie plants and few, if any, pocket gophers.
Although still chiefly grassland inhabitants, bullsnakes often sheltered beneath downed logs and in tree cavities. They depended on deep burrows to safely overwinter below the frostline. Radio telemetry tracking revealed that our bullsnakes moved regularly among upland hills, wetlands, and wet meadows. However, they're surrounded by unwelcoming lands and roadways that often are barriers or death traps. Like five-lined skinks, bullsnakes are in a squeeze from habitat loss, degradation, and fragmentation.
We're continuing to track and search for bullsnakes in 2018, now that we have a revised profile of potential habitat. Meanwhile, our preliminary findings are already informing conservation. For example, we've advised land managers to leave a few logs and scattered hollow trees when clearing grasslands, and we've alerted them that some at-risk species use certain cattle pastures and may benefit from practices such as prescribed fire and moderate grazing.
Habitat restoration and remnant prairie protection are key pieces of the puzzle. Still, questions remain. How much space do these bullsnakes need to thrive? Where are opportunities to connect wildlife habitats in this "working landscape" where agriculture and wild things meet? Are the snakes thriving in cattle pastures or are they simply using remaining habitats? Can modifying grazing and grassland management practices help bullsnakes, other wildlife, and cattle? Collaboration with private landowners, cattle producers, and conservation grazing specialists may yield answers.
Bullsnakes face other threats unrelated to habitat. Sadly, some people intentionally kill snakes, motivated by misplaced fear. In truth, bullsnakes are non-venomous constrictors that eat rodents and other small animals, including those that feed on crops or are carriers of Lyme disease. The snakes go about their business quietly and largely unseen. Hiding, camouflage, and escape are their first lines of defense. They can put on a tough-guy act when cornered: a loud raspy hiss and a vibrating, rattle-less tail that mimics a rattlesnake. Savvy landowners, though, value these beneficial neighbors and simply let them be on their way. Our research project encourages this sort of understanding, and the Nongame Wildlife Program is stepping up its work promoting snake appreciation and protection statewide.
Although the Minnesota River Reptile Project focuses on two rare species, its importance extends far beyond these creatures. The prairies they inhabit are some of the rarest, most imperiled ecosystems in Minnesota. Our rare reptiles are ambassadors for vulnerable and potentially restorable habitats along the Upper Minnesota River Valley—a priority landscape under Minnesota's Wildlife Action Plan, Prairie Conservation Plan, and the Upper Minnesota River Valley Master Plan.
Our project weaves together these initiatives for the greatest benefit. For example, one of our skink study sites is a conservation easement where the Nongame Wildlife Program led a Prairie Plan restoration project to benefit species dependent on prairie rock outcrops. This lies next to another study site on managed public lands. This approach allows us to study a larger habitat complex and use new knowledge to further restorative conservation.
Strong public and private partnerships are crucial for conservation. Our team has been supported by many cooperators, including conservation-minded private landowners whose involvement and knowledge are vital. With our partners, we're translating findings into more effective action, part of an ongoing, collaborative process of adaptive conservation.
Humans are a part of—not apart from—our environment. Native ecosystems are interdependent in complex and often unseen ways. When species are declining or lost, it signals that the "web of life" that supports us is unraveling. Reconnecting native habitats is good for reptiles, for other wildlife, and for people. Why conserve and restore these habitats? It's about more than vistas; it's about the ancient bones beneath our feet and the life these landscapes support: a renaissance of rocks, reptiles, and prairie supported by our combined efforts.