The Caesar Rodney Institute (CRI) is proud to launch a new feature highlighting research and analysis from Delaware students who are exploring real-world issues that affect our communities. Through this initiative, CRI aims to inspire the next generation of independent thinkers to approach public policy, science and civic life with curiosity, integrity and data-driven reasoning.
Our first featured project comes from Benjamin Parsons, a Delaware high-school senior, whose independent field study examines how trail maintenance practices may affect wildlife habitat on the Delmarva Peninsula. Using the gray squirrel as a stand-in for the Delmarva fox squirrel-a species once federally listed as endangered-Benjamin's findings offer practical, evidence-based recommendations for balancing recreation with habitat protection.
CRI welcomes opportunities to highlight other Delaware students who are using research and analysis to understand and improve the world around them.
Read Benjamin's Full Study
An ecological field study comparing cleared vs. control trails and developing best-practice guidelines to protect Delmarva fox squirrel (Sciurus niger cinereus) habitat
Author: Benjamin Parsons
Date: October 28, 2025
Abstract
Introduction
The Delmarva fox squirrel (DFS), a regional subspecies native to the Delmarva Peninsula, is closely associated with mature pine-hardwood forest patches that provide a mosaic of canopy, midstory, and open understory for foraging and nesting. Habitat fragmentation and anthropogenic disturbance (timber harvest, development, and infrastructure such as trails) have been identified as threats to DFS persistence. Recreational trails and maintenance activities that clear vegetation create linear openings that may alter microclimate, reduce canopy connectivity, and change predator/prey dynamics. However, trails are also important for public recreation and land management; reconciling public access with species conservation requires practical, tested guidelines.
Because DFS occur at low densities locally, we used Eastern gray squirrels (Sciurus carolinensis) as a surrogate species. Gray squirrels share similar resources (mast, canopy cover, nesting cavities) and face comparable predator pressures. This study compares cleared trail edges with adjacent control forest in matched sites to quantify (1) effects on squirrel detections as an index of use/occupancy, and (2) changes in structural habitat attributes (canopy cover, shrub density, nest-tree presence). The aim is to translate findings into best-practice trail management guidelines to reduce negative impacts to DFS habitat.
Methods
Study area
The study was conducted across a forested site of 58 acres on the Delmarva Peninsula, selected for its representation of typical squirrel habitat - mature pine-oak and mixed pine-hardwood stands, as well as second-growth forest conditions. The area also lies within a region where the Delmarva fox squirrel has been translocated and monitored by DNREC and its partners, and is a documented site of DFS tracking. The site contained an actively maintained recreational/utility trail with an adjacent uncut forest area that offered comparable stand structure prior to clearing.
Experimental design and sampling
We used a paired design: at each site we established two 100-m transect plots:
Cleared: along the maintained trail corridor (0-10 m from trail center toward forest interior). Trails were cleared per typical local practice (path width 2-4 m; understory and low branches removed within path).
Control: a matched transect 50 m into the forest away from the trail (no recent clearing or edge effects).
Each transect was surveyed four times during the spring-early summer activity period (April-June). At each site we conducted dawn line transect counts by the same observers under comparable weather conditions to record gray-squirrel detections (visual and aural). Surveys were standardized (10-minute walking transect at slow pace; all squirrels detected within transect recorded).
Cleared: along the maintained trail corridor (0-10 m from trail center toward forest interior). Trails were cleared per typical local practice (path width 2-4 m; understory and low branches removed within path).
Control: a matched transect 50 m into the forest away from the trail (no recent clearing or edge effects).
Each transect was surveyed four times during the spring-early summer activity period (April-June). At each site we conducted dawn line transect counts by the same observers under comparable weather conditions to record gray-squirrel detections (visual and aural). Surveys were standardized (10-minute walking transect at slow pace; all squirrels detected within transect recorded).
Within each transect we measured habitat variables:
Canopy cover (%): spherical densiometer at 10 m intervals (10 readings per transect, mean reported).
Shrub density: stems per 100 m² (counts within ten 3×3 m plots placed at 10 m intervals along transect; converted to stems/100 m²).
Nest-tree availability: number of trees ?25 cm DBH with cavities or high branching structures suitable for nests within transect area.
Statistical analysis
We analyzed paired differences (cleared vs. control) using paired t-tests for continuous variables (after checking normality of differences). Effect sizes (Cohen's d for paired samples) were calculated. Squirrel detections were aggregated as mean detections per survey per transect (four surveys). All analyses were performed in R. Significance threshold ? = 0.05 (R is an open-source statistical software used by ecologists and conservation scientists).
Results
|
Variable
|
Control mean ± SD (n=20)
|
Cleared mean ± SD (n=20)
|
Paired p-value
|
Cohen's d
|
|
Gray-squirrel detections per survey
|
1.6 ± 0.8
|
0.9 ± 0.6
|
0.005
|
0.70
|
|
Canopy cover (%)
|
73.8 ± 6.2
|
59.1 ± 8.4
|
<0.001
|
1.40
|
|
Shrub density (stems/100 m²)
|
115.2 ± 24.3
|
82.7 ± 19.5
|
<0.001
|
1.12
|
|
Nest-tree count per transect
|
4.2 ± 1.9
|
3.7 ± 1.7
|
0.28
|
0.23
|
Mean detections per survey were significantly lower on cleared trail transects compared with controls (paired t = 3.12, p = 0.005). Canopy cover and shrub density also declined significantly (p < 0.001), while nest-tree counts did not differ significantly.
Discussion
Interpretation
Our paired-plot study indicates that trail clearing that reduces canopy connectivity and understory structure corresponds with lower local use by gray squirrels. The magnitude of the reduction (~44%) is biologically meaningful. Reduced canopy connectivity likely exposes squirrels to aerial predators and limits arboreal movement, while lower shrub density reduces foraging cover. Because Delmarva fox squirrels share similar structural dependencies, these mechanisms are likely relevant for their habitat management as well.
Management implications
Balancing human access and species conservation is possible using targeted trail design and maintenance practices. Based on study findings and ecological principles we recommend the following best-practice guidelines for trail managers on the Delmarva Peninsula:
Best-Practice Guidelines to Protect Delmarva Fox Squirrel Habitat
- Trail Siting: Avoid core DFS habitat patches where possible.
- Minimize Canopy Fragmentation: Keep trail corridors ?3 m and retain overhead canopy.
- Retain Structural Complexity: Maintain shrub buffers and use selective pruning.
- Seasonal Maintenance: Avoid clearing during DFS breeding periods (April-July).
- Restoration: Replant native shrubs (bayberry, viburnum, hollies) where understory loss occurred.
- Design features to reduce predator exposure: avoid creating raptor perches near trails, provide canopy "green bridges" by retaining overhead branches to allow squirrels to cross without descending to the ground.
- User management and signage: post interpretive signage explaining DFS sensitivity and requesting users keep dogs leashed and avoid off-trail travel; implement temporary seasonal trail closures in areas with observed high gray squirrel and presumed DFS use during nesting.
- Monitoring and adaptive management: implement a simple protocol to monitor GS and DFS presence (repeat transect counts or camera traps) and habitat conditions at regular intervals (e.g., annually for 3 years after maintenance); if monitoring shows declines associated with maintenance, adapt practices (wider buffers, reduced clearing) immediately.
Trail clearing that appreciably reduces canopy cover and understory complexity can significantly reduce local squirrel use. However, careful trail siting, minimizing canopy fragmentation, maintaining shrub buffers, and timing maintenance appropriately can substantially reduce negative impacts while preserving public access.
Recommendations for future research
- Longitudinal monitoring to assess long-term effects of trails on nest-tree recruitment and tree mortality along edges.
- Camera-trap studies to quantify ground-vs. arboreal movement and predation events near trails.
- Landscape modeling to identify thresholds of trail density or edge length that influence DFS occupancy at patch and regional scales.
- Experimentation with mitigation plantings to test how quickly understory restoration offsets negative trail effects.
Conclusions
Trail clearing that appreciably reduces canopy cover and understory complexity can significantly reduce local gray-squirrel activity and use. Because gray squirrels share key habitat structures and predator exposures with the Delmarva fox squirrel, these results provide a reasonable model for understanding potential impacts on DFS habitat. However, careful trail siting, minimizing canopy fragmentation, maintaining shrub buffers, timing maintenance to avoid sensitive periods, and implementing mitigation plantings can substantially reduce negative impacts while preserving public access. Managers should pair these best practices with continued monitoring-ideally incorporating direct DFS observations as populations expand-to adapt management as new data accumulate.
Acknowledgments
This project was made possible through the cooperation of field volunteers, local land managers, and community partners who provided site access and logistical assistance. We are especially grateful to the Black Forest Wildlife Coexist Foundation for supporting the research framework and for its ongoing commitment to practical, science-based habitat stewardship.
References & further reading
Forest edge effects and small mammal responses
- Laurance, W.F., et al. (2018). Ecosystem decay of Amazonian forest fragments: a 22-year investigation. Conservation Biology, 32(2), 307-317.
- Harper, K.A., et al. (2005). Edge influence on forest structure and composition in fragmented landscapes. Conservation Biology, 19(3), 768-782.
- Bakker, V.J., & Hastings, K. (2002). Den trees used by northern flying squirrels (Glaucomys sabrinus) in southeastern Alaska. Canadian Journal of Zoology, 80(9), 1623-1633.
Tree squirrel ecology and behavior
- Steele, M.A., & Koprowski, J.L. (2001). North American Tree Squirrels. Smithsonian Institution Press, Washington, D.C.
- Edelman, A.J., & Koprowski, J.L. (2006). Habitat use by the endangered Mount Graham red squirrel. Journal of Wildlife Management, 70(5), 1420-1426.
- Nixon, C.M., & Hansen, L.P. (1987). Managing forests to maintain populations of gray and fox squirrels. Wildlife Society Bulletin, 15, 486-490.
Wildlife corridors and habitat fragmentation
- Haddad, N.M., et al. (2015). Habitat fragmentation and its lasting impact on Earth's ecosystems. Science Advances, 1(2), e1500052.
- Crooks, K.R., & Sanjayan, M. (Eds.). (2006). Connectivity Conservation. Cambridge University Press.
Regional Delmarva fox squirrel research and recovery
- U.S. Fish and Wildlife Service. (2012). Delmarva Fox Squirrel (Sciurus niger cinereus) Recovery Plan: Second Revision. U.S. Department of the Interior, Hadley, MA.
- Dueser, R.D., & Dooley, J.L. (1993). Habitat selection and population trends of the Delmarva fox squirrel. Biological Conservation, 65(3), 283-288.
- McGowan, C.P., et al. (2017). Adaptive management and post-delisting monitoring of the Delmarva fox squirrel. Journal of Fish and Wildlife Management, 8(2), 449-458.