Michael J. Chamberlain

A MULTI-RESOLUTION ASSESSMENT OF RACCOON DEN SELECTION

Abstract Many studies have been conducted on the ecology of raccoons (Procyon lotor), while few have examined raccoon den-site selection, particularly in agricultural and prairie landscapes. Furthermore, no studies have examined selection of den sites at multiple spatial scales. We examined den-site selection for 48 raccoons during 1997–1999 in an agricultural landscape in the Black Prairie physiographic region of east-central Mississippi, USA. Den types selected by raccoons differed by gender and season. Females used more cavity dens during young rearing, whereas males selected ground dens and brush piles. We found that den sites were located closer to crop fields, roads, and macrohabitat edges than random points. At the landscape level, den sites were associated positively with woody patch size, amounts of woody and grass edge, number of available patches of crop fields, and available area of lakes and ponds. Composition of habitats around den sites differed from composition of habitats within home ranges, and this difference also was noted by gender. Female raccoons selected crop fields, whereas males selected lakes/ponds relative to composition of habitats within their respective home ranges. Our results indicate the importance of tree cavities to females during young rearing, particularly on prairie landscapes. Furthermore, our findings suggest that on prairie landscapes, availability of foraging habitat and water may influence den-site selection. We suggest that raccoons select den sites based on a perceived arrangement of required resources and that landscape configuration is important in the den-selection process. Additionally, our findings offer evidence that managers may selectively remove den sites as a nonlethal means of managing predation by raccoons.

Regulation of space use in a solitary felid: population density or prey availability?

Home range size in birds and mammals appears to be influenced by a number of factors including food availability, body mass and population density. However, few studies have convincingly shown population density to influence the extent of space use in a population of free-ranging carnivores without a corresponding increase in food availability. We investigated the relative effects of food availability, body weight and increased density on the size of adult bobcat, Lynx rufus, home ranges and core areas in Mississippi, U.S.A. during 1989–1997. We observed an increase in population density and a decrease in annual mean home range and core area sizes for males and females during this 9-year study. Population density explained 64% and 56% of the variation in home range size for males and females, respectively, whereas food availability and body weight failed to explain the observed reduction in bobcat home range size. Population density was also the most important variable explaining variation in core areas for both sexes, although food availability also appeared to contribute to variation, especially for females. We suggest that population density should be considered along with energy acquisition and metabolic factors such as food availability and body size when investigating variability in home range and core area sizes of mammals.

Space use and multi-scale habitat selection of adult raccoons in Central Mississippi

Raccoons (Procyon lotor) are important furbearers and ecological generalists that exist in a variety of landscapes. Numerous studies have examined raccoon space and macrohabitat use, but information detailing these parameters within pine-dominated landscapes is lacking. Furthermore, no studies using radiotracking have examined raccoon habitat use at multiple spatial scales. We radiomonitored 131 adult raccoons (99 M, 32 F) during 1991-1997 in central Mississippi, USA. We subsequently assessed space use and habitat selection at 3 spatial scales. Males maintained larger home ranges and core areas than females. Size of home ranges differed by season, but raccoons maintained similar-size core areas across seasons. Habitat use differed by gender only at the coarsest spatial scale. Raccoons consistently used mature (>30 years old) pine and hardwood habitats over other available habitats at all spatial scales. Although hardwood-dominated habitats were important to raccoons, our findings suggest that in pine-dominated landscapes, raccoons select multiple seral stages of pine. Raccoons also readily used ≤8-year-old pine habitats, likely because of increased foraging opportunities within these habitats, particularly, during spring and summer. Our findings illustrate the importance of juxtaposition of habitat types for raccoons in pine-dominated landscapes, specifically the availability of mature pine and hardwood habitats, as well as early-successional habitats capable of providing beneficial foraging resources. Additionally, our findings offer evidence that prescribed burning may alter landscape use by raccoons, providing the potential that manipulating burning frequencies may allow managers to manage raccoon habitat-use patterns.

Space Use and Habitat Selection by Female Louisiana Black Bears in the Tensas River Basin of Louisiana

Abstract Studies of space use and habitat selection of endangered species are useful for identifying factors that influence fitness of individuals and viability of populations. However, there is a lack of published information regarding these behaviors for the federally threatened Louisiana black bear (Ursus americanus luteolus). We documented space use and habitat selection for 28 female black bears in 2 subpopulations of the Tensas River Basin population in northeast Louisiana, USA. The Tensas subpopulation inhabits a relatively large (>300-km2) contiguous area of bottomland hardwood forest, whereas the Deltic subpopulation exists mainly in 2 small (<7-km2) forested patches surrounded by an agricultural matrix. Females on Deltic maintained smaller seasonal and annual home ranges than females on Tensas (all P < 0.04), except for females with cubs during spring. On Tensas, females with cubs maintained smaller home ranges than females without cubs during spring (P = 0.01), but we did not detect this difference on Deltic or in other seasons. Females on Tensas and Deltic exhibited differences in habitat selection when establishing home ranges and within home ranges (P < 0.001). Deltic females selected mature bottomland hardwood forests and avoided agricultural habitats at both spatial scales. Tensas females selected a mixture of swamps, mature and regenerating forests, and exhibited variation in selection across scale, season, and reproductive status. We suggest that differences in space use and habitat selection between Tensas and Deltic are at least partially due to habitat differences at the landscape (i.e., amount of forested habitat) and patch (i.e., food availability) scales. Our results contribute to the understanding of factors that influence space use and habitat selection by black bears and provide specific information on habitat types selected by Louisiana black bears to agencies involved in habitat protection and restoration for this threatened subspecies.

Survival and cause-specific mortality of adult raccoons in central Mississippi

The raccoon (Procyon lotor) provides recreational, aesthetic, and economic benefits throughout its range. Knowledge of survival and cause-specific mortality is necessary to understand dynamics of raccoon populations and enable effective management. Additionally, sportsmen in many Southeastern states have expressed interest in a summer raccoon hunting season; however, information on effects of summer hunting on raccoon survival and cause-specific mortality are unavailable. Consequently, we radiotracked 176 adult raccoons in central Mississippi during 1991-97. Annual survival differed (P = 0.031) between males (0.63 ± 0.09; x ± SE) and females (0.50 ± 0.10). Annual survival varied among years for males (P < 0.01), but not for females (P = 0.117). Cause of death was known for 55% of raccoon mortalities; legal harvest accounted for most (58%) known deaths. Annual survival did not differ (P = 0.356) between raccoons in the summer hunting (0.60 ± 0.06) and control (0.69 ± 0.06) areas. However, patterns of mortality varied between the summer hunting and control areas (P < 0.001), and seasonally (P = 0.003). Our data suggest implementing a summer raccoon ting season with conservative bag limits will not reduce raccoon populations by reducing annual survival.

Deciphering Ecological Barriers to North American River Otter (Lontra canadensis) Gene Flow in the Louisiana Landscape

For North American river otters (Lontra canadensis) in Louisiana, statewide distribution, availability of aquatic habitats, and the absence of physical barriers to dispersal might suggest that they exist as a large, panmictic population. However, the wide variety of habitat types in this region, and the dynamic nature of these habitats over time, could potentially structure river otter populations in accordance with cryptic landscape features. Recently developed landscape genetic models offer a spatially explicit approach that could be useful in identifying potential barriers to the movement of river otters through the dynamic aquatic landscape of Louisiana. We used georeferenced multilocus microsatellite genotypes in spatially implicit (STRUCTURE) and spatially explicit (GENELAND) models to characterize patterns of landscape genetic structure. All models identified 3 subpopulations of river otters in Louisiana, corresponding to Inland, Atchafalaya River, and Mississippi River regions. Variation in breeding seasonality, brought about by variation in prey abundance between inland and coastal populations, may have contributed to genetic differentiation among populations. It is also possible that the genetic discontinuities we observed indicate a correlation between otter distribution and access to freshwater. Regardless of the mechanism, it is likely that any genetic differentiation among subpopulations is exacerbated by relatively poor dispersal.

Space use, movements and habitat selection of adult bobcats (Lynx rufus) in Central Mississippi

Abstract Many factors influence bobcat (Lynx rufus) space use, movements and habitat selection, including prey distribution and density, season, breeding behaviors and intraspecific relationships. Knowledge of ranging behaviors and habitat selection is required to understand population dynamics and ecology of bobcats within temperate ecosystems. We radio-monitored 58 adult bobcats from 1989–1997 in central Mississippi. Males maintained larger home ranges and core areas than females, but sizes of these areas did not vary seasonally. Male bobcats moved at greater rates than females and bobcats moved at greatest rates during nocturnal periods. Movement rates were greatest during winter. Habitat selection at three spatial scales differed between genders and across seasons within gender. Our findings suggest that ≤8 y-old pine (Pinus spp.) habitats are important to bobcats, particularly females, as these habitats were selected by females at all spatial scales. However, our data also indicate that mature (>30 y) pine habitats are important to bobcats on our study area.

Spatial use patterns, seasonal habitat selection, and interactions among adult gray foxes in Mississippi

Knowledge of spatial use, habitat selection, movements, and survival of gray foxes (Urocyon cinereoargenteus) is essential for thorough ecological understanding and successful management of the species. Additionally, information detailing intraspecific spatial and temporal relationships is necessary to understand potential territorial and social behavior among individuals. We radiomonitored 37 (17 M, 20 F) adult gray foxes from 1991-97 in central Mississippi. Size of home range and core area did not differ between sexes, but did among seasons. Home range overlap was greatest for males and females sharing home ranges and least for neighboring males. Core area overlap was negligible, except for males and females who shared home ranges and were suspected of forming pair bonds. Habitat selection was similar between sexes and across seasons at all spatial scales. Home ranges and core areas of gray foxes contained greater proportions of mature pine (≥30-yr, Pinus spp.) habitats than available. Gray foxes consistently selected habitats that contained an abundance of small mammals. Movement rates were similar between sexes, but not across seasons or diel periods. Pair members frequently traveled together within their home ranges; however, neighboring males and females did not interact closely, suggesting a mutual avoidance reaction (territoriality). Annual survival rates were similar between sexes and across years. Our results suggest that spatial use patterns are not sex-specific and habitat selection is not sex- or season-specific However, gray foxes in our study exhibited differential movements within home ranges according to season, suggesting that although habitats used were seasonally similar, foraging patterns within these areas differed.

Spatio-temporal Relationships Among Adult Raccoons (Procyon lotor) in Central Mississippi

Abstract We monitored 131 (99 male, 32 female) radiocollared raccoons (Procyon lotor) from January 1991 to December 1997 on the Tallahala Wildlife Management Area, Mississippi. We examined inter- and intrasexual spatial relationships and temporal interactions among adults. Adult males frequently maintained overlapping home ranges and core use areas and some males maintained spatial groups that overlapped minimally with adjacent groups or solitary males, suggesting territoriality among groups. Males arranged in spatial groups were often significantly positively associated with each other; however, we observed instances of males who remained solitary and maintained exclusive home ranges and core areas. Adult females maintained exclusive home ranges and core areas during winter, but several females shared home ranges during other seasons. However, these females did not forage or den together and were significantly negatively associated with each other within shared areas, indicating that movements by these individuals were independent. Home range and core area overlap differed among seasons for males and females with neighboring or overlapping home ranges. Our findings suggest that social behavior in raccoons varies within the same protion of the landscape, ranging from solitary individuals to male social groups.

Efficacy of herbicides and fire to improve vegetative conditions for northern bobwhites in mature pine forests

Abstract Declining northern bobwhite (Colinus virginianus) populations during the past 30 years have prompted managers to seek ways to improve habitat quality for this species. Reductions in frequency of prescribed fire throughout considerable expanses of mature pine (Pinus spp.) forests have resulted in closed-canopy conditions, predominantly woody understory conditions, and a loss of early-successional habitats needed by bobwhites. Herbicides, particularly in conjunction with prescribed fire, may be useful for managing these pine forests to benefit the bobwhite and other early-successional species, but effects of herbicides in combination with fire are not well understood. Therefore, we used 3 similar-aged, mature pine stands to evaluate vegetative response to selective herbicides with prescribed fire with respect to bobwhite nesting and broodrearing habitats. Our treatments were imazapyr with fire, imazapyr combined with glyphosate with fire, and dormant-season prescribed fire only. Plant diversity tended to decline on herbicide treatments during the first year but increased substantially on imazapyr plots during the second growing season following a burn. Bobwhite food plants increased following application of imazapyr during the first growing season and were greater for both herbicide treatments than burning alone during the second growing season. Abundance of hardwoods declined on both herbicide treatments. However, no treatments produced bare-ground percentages known to be selected by bobwhites, and only prescribed fire alone created and maintained suitable escape cover. Overall, imazapyr with fire provided the greatest net improvement in vegetative conditions for bobwhites and retained floristic diversity. We recommend that managers target areas in which vegetative conditions have progressed to where burning alone is incapable of restoring early-successional plant communities needed by the bobwhite and other species and apply imazapyr with fire to create diverse, patchy habitat for bobwhites.