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Mississippi State University

Research Findings


Methods


Raccoons and wild turkey hens were monitored during 1996-97. Using raccoon locations taken from 1 April to 31 May (defined as entire nesting season), we generated 100% UD grids using a harmonic mean estimator in ARCVIEW. We used all locations taken on each hen from nest initiation until the termination of nesting effort to generate UD grids for hens during the nesting period. Grid-based UD provide grid-specific values for utilization, with smaller values indicating peaks in use. We set the grid cell size to a somewhat arbitrary 100 m because smaller cell sizes likely exceeded the resolution that triangulated telemetry locations provided to determine animal locations.

Once UD grids were developed for each raccoon and hen, we merged all grids for each species into 1 landscape-level grid. This allowed us to simultaneously examine cumulative raccoon and hen use across both areas. We chose to partition individuals by area because forest management practices, particularly burning and thinning regimes, differed greatly between areas.

Using area-specific landscape-level UD grids for raccoons and hens, we overlaid each grid onto a GIS landcover map for each area. We subsequently intersected each UD with the landcover map and queried ARCVIEW to represent stands across the landscape receiving greatest use by raccoons and hens. We then determined habitat attributes associated with grid cells receiving greatest use by each species. To provide 3-dimensional representations of species-specific UD across TWMA and GP, we used ARCVIEW 3D Analyst (ESRI, Redlands, California, USA) to create contour gradients of peaks and troughs in each landscape-level grid. Once features associated with peaks and troughs in 3-dimensional grid outputs were identified, we developed management recommendations designed to benefit wild turkey reproduction by increasing quality nesting habitat. Alternatively, recommendations were developed that should lower the quality of habitats across the landscape for raccoons, but increase quality of these same areas for reproductively active hens.

Results


Peaks in use by raccoons on TWMA occurred within 2 major habitat types: mature pine and pine stands <8 years-old. Other, less pronounced peaks, occurred in mature bottomland hardwood stands. Mature pine stands where peaks occurred were predominately burned >5 years prior. Most peaks within 0-8 year-old pine stands occurred within stands >3 years-old and <6 years-old. Nearly all troughs in raccoon use occurred within mature pine stands burned <3 years prior and mature mixed pine-hardwood stands.

Peaks in use by wild turkey hens most frequently occurred in mature pine (>30 years-old) stands. Further, many peaks occurred in stands burned <4 years prior. However, because burning only occurred on the western portion of TWMA during the study, hens captured and monitored on the eastern portion of TWMA did not have access to recently burned stands. Therefore, peaks in use on the eastern portion of TWMA occurred in mature pine stands burned >5 years prior.

Peaks in use by raccoons on GP occurred in pine stands >15 years-old. It should be noted that no prescribed burning occurred on GP during this study. Therefore, understory vegetation in these stands was dense and dominated by vine and hardwood saplings, rather than herbaceous vegetation. Grid cells indicating peak use by raccoons covered nearly 50% of GP, suggesting that nearly half of the area contained areas receiving greatest raccoon use. Without exception, grids receiving greatest use were within pine stands adjacent to streamside management zones or stands containing terrain created by ephemeral or perennial water. Troughs in raccoon use on GP occurred in mixed pine-hardwood stands >15 years-old. Similarly, peaks in use by wild turkey hens on GP occurred in pine stands >15 years-old and only 2 peaks occurred in mixed pine-hardwood stands.

In many instances, peaks in use for raccoons and wild turkey hens occurred within the same stand. This was particularly prominent on GP, where nearly all peaks for raccoons were consistent with peaks for hens. Most peaks in use for raccoons and hens on TWMA occurred in similar macrohabitat types. However, prescribed burning history differed between areas receiving peak raccoon and hen use. Hens in this study selected nest sites with great abundance of herbaceous growth; prescribed burning increases abundance of herbaceous growth in understory communities. In areas receiving prescribed burns on TWMA, peaks in hen use occurred in stands burned within 4 years prior to nest initiation. When available, the presence of habitats receiving prescribed burns likely provided hens the opportunity to nest in habitats less used by raccoons. Conversely, peaks in raccoon use in stands with a longer burning rotation likely resulted from increasing soft mast abundance in those habitats. Raccoon diet frequently shifts during spring to include soft mast as availability increases. Nest success in this study was low, regardless of nest location. Hence, it is unclear whether the observed differences in raccoon and hen UD peaks inferred any reproductive advantages to turkeys maintaining home ranges within areas receiving prescribed burns. Ancillary observations of broods on TWMA indicated that 10-15 broods occupied TWMA both during 1996 and 1997. Therefore, brood observation data indicated that hens did successfully nest on TWMA and the number of observed broods was considerably greater than during 1993-1995. Further, all but 2 broods each year were sighted in the western portion of TWMA where prescribed burning frequency increased during 1995-1997. Although based on ancillary observations, it is plausible that increased burn frequency on the western portion of TWMA ultimately increased nest success. However, whether this observed nest success resulted from decreased nest depredation is unclear. Since the completion of this study, considerable thinning has occurred in mature pine stands on the eastern portion of TWMA in response to management schemes directed at benefitting red-cockaded woodpeckers. It is likely that these changes, coupled with mandating increases in burning frequency within these stands, will produce habitat conditions associated with troughs in raccoon use on the western portion of TWMA.

On GP, peaks in use for both species frequently occurred within the same stands. I suggest that decreased habitat heterogeneity and the overall lack of prescribed burning during this study resulted in the observed similarities in use between raccoons and wild turkey hens. The lack of prescribed burning allowed understory vegetation in pine stands across GP to become rank with vine and woody growth. Increasing vine and woody growth likely resulted in increased soft mast abundance, creating quality foraging habitats for raccoons. Additionally, hens were likely limited in potential choices for nest sites and compared to other available habitats, pine stands > 15 years-old were most attractive for nesting. Only 2 nests on GP were located in habitats other than pine stands >15 years-old.