1. Trail Effects on the Abundance of Snowshoe Hare and Red Squirrel Along the Sourdough Trail in Winter
While neither species is listed as threatened, the snowshoe hare is an important food source for the “ESA threatened” Canada Lynx (Lynx canadensis) and must therefore be monitored to assure sufficient abundance to support Lynx recovery (Ellsworth and Reynolds 2006).
Citation:
Horsley, B. Trail Effects on the Abundance of Snowshoe Hare and Red Squirrel Along the Sourdough Trail. Winter Ecology. University of Colorado at Boulder, 2016.
Keywords:
Mammals, Winter, Ecology, Subalpine, Disturbance, Recreation, Lepus americanus, Tamiasciurus hudsonicus, Tracks, Negative effects.
File Size: 16.4mb
Study conducted by Bryan Horsley
CU Boulder EBIO Program
Winter Ecology 2016

2. Research Question Is there a negative “trail effect” on the abundance of snowshoe hares and/or red squirrels along the Sourdough trail in winter? I hypothesize that there is an effect and my research is designed to test this.
This research question was designed to provide the foundation for my research.
While this study is important in gaining a better understanding of the effects of recreational activities on wildlife, I think it is even more important when considered in a winter setting considering the vulnerability of mammals that overwinter in the subalpine. As we discussed in detail throughout the extent of this course they are already living near the edge of their energy and survival threshold and any added stress or challenge could push them over the threshold.

3. Snowshoe Hare (Lepus americanus)
Range: Canada, Alaska, Rocky Mtns, Appalachian Mtns
Remains active through winter
Mostly nocturnal or crepuscular
Leaps up to 12ft when moving quickly
Coat color plasticity
Food switching
Opportunistic: carrion!
Large heavily-furred rear feet
Short ears and tail
Canada Lynx: predator
Source: Reid 2006
Switches food source from grass, green vegetation, and berries (summertime) to woody sources (twigs and bark) in winter.
Primarily depends on camouflage to avoid predation but can move very quickly on snow when needed.
(Allen’s Rule): short ears

4. Red Squirrel (Tamiasciurus hudsonicus)
Range: Canada, Alaska, Northeast U.S., Rocky and Appalachian Mtns.
Remains active through winter
Conspicuous forest resident
Eats pine seeds primarily
Also nuts, fungi, fruit, sap, birds, eggs
White eye ring
Ears tufted in winter
Makes insulated nest
Prefers tree cavities
Source: Reid 2006
Interesting to note the similarities in these two overwintering mammal species:
Similar range
Opportunistic feeding strategies
Small ears (Allen’s Rule of smaller appendages perhaps)
Increased fur insulation

5. Background
“Quiet, non-consumptive” recreation have negative impacts on wildlife
Non-motorized, non-hunting activitites
Seemingly low-impact activities
A challenging ethical issue (personal)
Prior to looking into this topic I didn’t really comprehend the extent to which seemingly “low impact” activities like hiking, birdwatching, kayaking, skiing, mountain biking, etc. really can affect wildlife and the natural unbuilt environment as a whole.
I always pointed the finger at the snowmobiles, dirt bikes, jeeps, and hunters for exploiting and disturbing the backcountry. The noise, exhaust odor, torn up dirt and vegetation, and apparent total lack of respect for the natural world was always (and still is) sad and frustrating to me.
Now I look at low-impact (quiet, non-consumptive) activities in a new light. While I don’t plan to quit recreating in nature, I will do it with more attention and awareness than before.
It’s this question “How do humans and nature coexist” that really provides the motivation for this study and presentation.
Source: Reed & Merenlender 2008

6. Negative effects of recreational trails
Spook and flee - wildlife driven away from trail.
Less bird nesting near trails (Miller, et al. 1998).
Dogs increase wildlife response (Banks & Bryant 2007).
Frequent short-term disturbances can result in long term changes
With increasing popularity of outdoor recreation comes increasing pressure on wildlife communities.
These deer near Wonderland Lake didn’t seem to mind my presence (although that buck was keeping a close eye on me)
It seems like certain species do adapt to the presence of humans: highly adaptable opportunist species like coyote, crow, magpie, mice, rat, coon, etc.
While other species that have more specific food source or habitat requirements don’t do so well.

7. A Potential Cascade Effect on Snowshoe Hare
Snowshoe hare is regularly flushed from feeding near trail
Wasted energy running  Didn’t eat enough  Malnutrition  Death
Moves away from trail area permanently  Change in habitat structure
Snowshoe hare no-longer in area
Impacts on predators (Lynx canadensis)  No food  Leave or die
Hares no-longer eating  Changes in vegetation structure (more growth)
Hare predators gone
Predator release effects on other animals  Imbalance in numbers
Predator range reduced  Lowered predator population
Changes in vegetation structure
Change in habitat stability for other inhabitants
Supporting further predator release benefits  Greater imbalance
Based on a flow diagram in Wildlife and Recreationists: Coexistence Through Management and Research (Knight and Gutzwiller, 1995).
This outline highlights a possible cascade effect on a snowshoe hare, in a worst case scenario.
Potential scenario of negative impacts on snowshoe hare stemming from seemingly low-impact events on a trail.
This isn’t what I’m suggesting is always the case, I’m simply presenting this as a potential worst-case scenario for consideration.
A hare could just be spooked from the trail and then come back 10 minutes later and keep eating.
It all depends on the frequency an regularity of disturbance and the ability of the species to adapt to the disturbance.
This does matter to the recovery efforts of Canada Lynx (Lynx canadensis).

8. Methods
Survey 4 transects (2 meter W x 0.5 km L) for tracks in the snow
2 transects on the Sourdough trail
2 transects 0.2 km off-trail, parallel to the on-trail transects
Compare on-trail vs. off-trail track abundance of each species (SS, SQ)
Used Garmin GPS enabled cyclo-computer to map routes and measure distance of each transect.
Used handheld compass to maintain parallel line to SD trail when off-trail. Also followed slope contour and used tree shadows to maintain heading.
At end of on-trail segment, used Garmin device to measure ~0.2 km (~656 ft) distance to start of off-trail transect (roughly perpendicular to trail).
Literature review suggested that various species are impacted at various distances and in response to various activities (snowmobiles and dogs caused impacts at greater distances than hikers).
This 0.2 km distance I selected was well beyond any documented impact distances for “quiet, non-consumptive” activities.
Completed three days of surveying but had to throw out one day due to inclement weather conditions (snow was filling in tracks on the off-trail segment so it was not a good comparison with the on-trail data we collected that day).
Low impact ski technique demonstrated by my trusty research assistant Dave M.

9. Track Identification
Squirrel left
Snowshoe hare right

10. Alternate Hypothesis:
Null Hypothesis:
Proximity to the Sourdough trail has no effect on the abundance of snowshoe hares and/or red squirrels.
Alternate Hypothesis:
Proximity to the Sourdough trail does have an effect on the abundance of snowshoe hares and/or red squirrels.
Before showing the results, a quick review of my hypothesis.
Study goal was to look at both species, both together and independently.

11. Results
Both species showed a “trail effect” correlation toward greater track abundance off-trail compared with the on-trail transects.
While this trail effect was not significant for red squirrels (P-value 0.2), the effect was significant for snowshoe hare (P-value of 0.01).
Total sets of tracks recorded were 228 SS, and 297 SQ
On-trail: 123 SQ and 60 SS.
Off-trail: 174 SQ and 168 SS.

12. Analysis Reject null hypothesis for snowshoe hare
There is a negative trail effect on snowshoe hare based on my research
Accept null hypothesis for red squirrel
There is not a negative trail effect on red squirrel based on my research
With null hypothesis rejected for SS I recommend a more serious look at the potential long-term negative impacts as discussed in my intro.
It’s interesting that I did find a negative trail effect for snowshoe hare despite the fact that they are nocturnal or crepuscular. I would think that this would alleviate stress on them from trail usage if they are active when there are significantly less people around.
Further research should be done to further support and refine my findings.
Perhaps management could be improved to minimize impacts on affected species?

13. Conclusion Results suggest a need for more ecology-based management
Trail placement / re-routing?
Usage types
Regulations
Seasonal usage (trails closed for mating)
Additional research
Which species are most impacted?
How can pressure be alleviated?
My research, in combination with abundant past research suggests that wildlife and plant communities are significantly impacted by the presence of humans, despite how low-impact the activity time may seem.
This fact suggests to me that it is of great importance, for the sake of protecting biodiversity and to achieve a harmonius coexistence between humans and nature, that the management of natural recreation areas take this information into account.
All impacts on wildlife should be taken into account and potential cascading effects should be considered when looking at recreational use policies and trail placement.
If this is done, negative impacts on wildlife can be reduced.

14. Questions?

15. Sources
Banks, P. B., & Bryant, J. V. (2007). Four-legged friend or foe? Dog walking displaces native birds from natural areas. Biology letters, 3(6),
Ellsworth, E., & Reynolds, T. D. (2006). Snowshoe hare (Lepus americanus): a technical conservation assessment. USDA Forest Service, Rocky Mountain Region.
Knight‪, Richard L. and Kevin Gutzwiller Wildlife and Recreationists: Coexistence Through Management and Research. Island Press, Washington D.C.
Miller, S. G., Knight, R. L., & Miller, C. K. (1998). Influence of recreational trails on breeding bird communities. Ecological Applications, 8(1),
Reed, S.E. and A.M. Merenlender Quiet, nonconsumptive recreation reduces protected area effectiveness. Conservation Letters, 1(3),
Reid, Fiona A Mammals of North America. Peterson Field Guides. Houghton Mifflin Company, New York.