Pellet Survey Results 2024 (Formal).docxPELLET COUNT RESULTS
2024
Mass Audubon Conservation Science
Written by Andrea Bickford, TerraCorps 2023-2024
OVERVIEW
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Photo credit: Hillary Truslow
North American White-tailed deer (Odocoileus virginianus) populations have increased in response to human alteration to the environment and the absence of hunting pressure by humans
and animal predators. Now considered ecologically overabundant across much of the northeast, white-tailed deer alter forest ecosystem function and composition by increasing browsing
pressure. Overbrowsing has been shown to negatively impact plant biodiversity, productivity, and tree stand regeneration, contributing to the decline and loss of several hardwood tree
species, understory shrubs, and herbaceous plants. These impacts have cascading adverse effects on other taxonomic groups, including some birds, herptiles, and invertebrates. Humans
also experience adverse effects of elevated deer densities, including increased car accident rates and economic losses to agriculture, silviculture, and horticulture industries. Mass
Audubon sanctuaries are seeing some of the impacts of deer overpopulation. By enacting active deer monitoring, Mass Audubon can monitor changes over time and inform decision-making
and adaptive management.
GOALS & OBJECTIVES
The success of our surveys relied on several key objectives: recruiting volunteers, gathering data, informing management, and monitoring changes. We began by recruiting and educating
volunteers from Mass Audubon and UMass Amherst, including students and professors. These volunteers were trained to accurately identify scat and follow the survey protocols. To evaluate
the selected sanctuaries, we needed to gather quantitative data. We used pellet counts to estimate deer density and population size, with volunteers conducting surveys and recording
these counts in each plot. The data collected will guide future management decisions at Mass Audubon sanctuaries, such as determining the need for a hunting program. These surveys will
be conducted annually, with some sanctuaries assessed every year and others every two years. This annual monitoring will enable Mass Audubon to track changes over time, adapt management
strategies as needed, and gain a deeper understanding of local deer population dynamics.
METHODS
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Photo credit: Andrea Bickford
In the 2024 field season, volunteers evaluated six wildlife sanctuaries: Whetstone Wood, Laughing Brook, Arcadia, High Ledges, Graves Farm, and Pleasant Valley. Each survey covered 4
miles of transects with 52 plots per mile, totaling 208 plots per sanctuary, though some sanctuaries had varying numbers of plots due to landscape conditions. Volunteers used geo-referenced
PDFs created in ArcGIS Pro and Avenza Maps to find their assigned plots. At each plot, they conducted pellet surveys by defining a 4-foot radius with a stake and pre-measured string,
identifying and counting the number of pellet piles within that radius, and recording the data on a sheet. The data from each sanctuary was then compiled and analyzed using the semi-automatic
PELLET procedure in Excel, which allowed us to calculate the average deer density for each sanctuary.
RESULTS
Thanks to our dedicated team of 77 volunteers, we surveyed 24 miles of transects across 6 sanctuaries in western Massachusetts. Out of 1190 plots surveyed, 241 contained pellet groups.
In total, 328 pellet groups were recorded across all sanctuaries.
Our deer density estimates are summarized in the table below:
Wildlife Sanctuary Name
Mean Population Density (deer/sqmi)
Whetstone Wood
45.4
Laughing Brook
34.3
Arcadia
104.3
High Ledges
72.6
Graves Farm
86.4
Pleasant Valley
22.1
Table 1. Mean population density estimates (deer/sqmi) at Mass Audubon wildlife sanctuaries.
DISCUSSION
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Figure 1. A graph displaying the mean population density estimates of white-tailed deer at west Mass Audubon sanctuaries resulting from pellet surveys conducted in the 2024 field season.
20 deer per square mile is the threshold at which we begin to see the negative effects of overabundant deer. MassWildlfe’s deer density goal is within 12-18 deer/sqmi.
MassWildlife reports that most of western Massachusetts meets the state's goal of 12-18 deer per square mile. However, at densities of 20 deer per square mile, negative impacts begin
to emerge. All Mass Audubon sanctuaries assessed have deer densities exceeding this threshold.
Based on the current vegetation conditions at our sanctuaries, we anticipated the highest deer density at Arcadia and the lowest at Pleasant Valley. Our results confirmed these expectations.
We also expected Laughing Brook to have a deer density similar to Arcadia, but the results showed it to be much lower. Surprisingly, Graves Farm had a higher density than expected,
while High Ledges aligned with our predictions.
Sanctuaries near the Connecticut River, such as Arcadia, High Ledges, and Graves Farm, have higher densities. These areas have many fields and agricultural activities in or around the
sanctuary, suggesting a potential relationship between fields and deer density, though further research is needed to confirm this.
Laughing Brook's deer density is lower than expected. We speculate that the food supply there might be exhausted, reducing the area's deer carrying capacity. Another possibility is that
the current vegetation condition doesn't reflect the present deer density due to time lags; today's vegetation might be the result of high deer densities from a decade ago. This is
speculative, and more data is required.
To establish trends over time, it's crucial to continue these surveys. The ongoing support of our volunteers and neighboring property owners is essential for conducting these surveys
in the coming years.
ACKNOWLEDGEMENTS
We want to thank everyone who made these surveys possible, including The City of Northampton, The Town of Hampden, and private property owners who allowed us access to their land for
the purpose of this research. We’d especially like to thank the volunteers for contributing substantially to collecting data, monitoring daily weather conditions, and reporting on the
state of Mass Audubon sanctuaries.
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Photo credit: Kelly Klingler