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Despite having been used for centuries to protect livestock and manage game populations, lethal predator control remains controversial. Several recent reviews of effects of predator control on prey populations concluded that in most cases predator reduction benefited prey populations (e.g., increased prey survival, abundance, or reproduction). However, each review reported a number of cases in which predator reduction had no discernible impact on monitored prey. We suggest that most predator removal efforts can be considered as a spatially structured harvest with non-harvested areas surrounding the predator removal area. As a result, immigration from non-harvested areas permits rapid recovery of predator populations and can potentially reduce efficacy of removal efforts. We used predator harvest and track-count data collected at the Joseph W. Jones Ecological Research Center to calculate the annual finite rate of population growth (λ) over a 14-year period. Removal data yielded an average λ = 1.33 ± 0.67 (± SE). Because λ did not differ from 1.0 (N = 13, t = 1.17, P = 0.27), predator removals occurring during 1 year clearly did not result in reduced removals following year. Moreover, during this same period track counts of all mesomammal predators yielded an average λ = 1.06 ± 0.22 that also did not differ from 1.0 (N = 13, t = 0.44, P = 0.80), providing further evidence of stable predator populations. We also reviewed 119 published studies to determine if similar predator population growth rates were observed. Of the reviewed studies, 20 contained sufficient information (i.e., at least 2 removal periods and number of removals reported) to calculate estimates of λ. Because these studies often had multiple study sites and removal periods, we were able to calculate 84 λ estimates. The average λ was 1.15 ± 0.14 and did not differ from 1.0 (N = 84, t = 1.15, P = 0.25). Our analyses provide evidence that predators recover quickly following harvest and suggest that adjacent non-harvested areas serve as a source of immigrating predators as would be expected under a spatially-structured harvest model. We argue that efficacy of predator control is increased when the area being managed is large and prey species are temporally vulnerable. We also suggest that predator diversity affects outcome of predator control efforts and predict that predator control is more likely to be effective when there are few predator species due to decreased opportunity for compensatory predation. We postulate that effective predator control becomes increasingly difficult as deviations from these criteria increase, and in some cases these deviations may be responsible for misinterpreting the role of predators on prey populations. Prior studies of effects of predator control on prey populations either did not collect or did not report sufficient data to evaluate our predictions. Future research should report sufficient data to allow evaluation of our criteria. Of particular importance are data concerning efficacy of the removal effort (i.e., what proportion of the predator population was removed).

The ecological restoration of fire‐suppressed habitats may require a multifaceted approach. Removal of hardwood trees together with reintroduction of fire has been suggested as a method of restoring fire‐suppressed longleaf pine (Pinus palustris) forests; however, this strategy, although widespread, has not been evaluated on large spatial and temporal scales. We used a landscape‐scale experimental design to examine how bird assemblages in fire‐suppressed longleaf pine sandhills responded to fire alone or fire following mechanical removal or herbicide application to reduce hardwood levels. Individual treatments were compared to fire‐suppressed controls and reference sites. After initial treatment, all sites were managed with prescribed fire, on an approximately two‐ to three‐year interval, for over a decade. Nonmetric multidimensional scaling ordinations suggested that avian assemblages on sites that experienced any form of hardwood removal differed from assemblages on both fire‐suppressed sites and reference sites 3–4 years after treatment (i.e., early posttreatment). After >10 years of prescribed burning on all sites (i.e., late posttreatment), only assemblages at sites treated with herbicide were indistinguishable from assemblages at reference sites. By the end of the study, individual species that were once indicators of reference sites no longer contributed to making reference sites unique. Occupancy modeling of these indicator species also demonstrated increasing similarity across treatments over time. Overall, although we documented long‐term and variable assemblage‐level change, our results indicate occupancy for birds considered longleaf pine specialists was similar at treatment and reference sites after over a decade of prescribed burning, regardless of initial method of hardwood removal. In other words, based on the response of species highly associated with the habitat, we found no justification for the added cost and effort of fire surrogates; fire alone was sufficient to restore these species.

The reproductive ecology of male Crotalus adamanteus Beauvois (Eastern Diamond-backed Rattlesnake) from southwestern Georgia (Joseph W. Jones Ecological Research Center, Baker County) was studied from 14 August 2003 to 14 August 2006. Few studies provide information on reproduction of free-living Eastern Diamondbacked Rattlesnakes, and no information is available on the seasonal relationship of plasma sex steroids of males to changes in the reproductive organs (e.g., mass of the testis and kidney) and the mating season. Here, the main goals were to determine whether: (i) males show variation in concentrations of plasma testosterone (T) during the active season (late March through November), (ii) males have elevated (peak) concentrations of plasma T during the single mating season, which has been documented to occur from late summer through early fall in nearby populations, and (iii) there are seasonal changes in length, width, and mass of the testis and kidney during the active season, particularly during the breeding period. There was a significant difference in mean concentrations of plasma T among seasons, with levels in summer significantly greater than those of spring, and levels in spring and fall were not significantly different. Testis mass and width, but not length, varied significantly across seasons. Testis mass paralleled elevated levels of plasma T, with peak mass occurring in the summer. Similarly, testis width was significantly greater in summer than in fall, but there was no significant difference between summer and spring, nor between spring and fall. We found no significant seasonal changes in any of the kidney measurements. Bisexual pairings were coincident or followed the occurrence of elevated levels of plasma T and changes in testis size; however, despite frequent observations, copulations were not observed. Nonetheless, our results support a mating season of late summer/early fall for the present population of Eastern Diamond-backed Rattlesnakes.

Until approximately 20 years ago, mammalian predators were actively pursued by hunters and trappers for both sport and economic gain. However, during the past two decades fur prices have fallen precipitously, and sport hunting and trapping of mammalian predators is at an all-time low. Some suggest that decreased hunting and trapping pressure on mesomammal predators (e.g., raccoons, opossums, bobcats, foxes, coyotes, etc; hereafter, mesopredators) has resulted in increased mesopredator populations and a decline in many prey species. The role of mesopredators within southern forests is controversial, and there are few empirical studies on which to base management and political decisions regarding predation issues. Moreover, the few studies that do exist focus on the response of a single species or are of too short duration to fully understand the long-term effects of removal efforts. This study will provide empirical, long-term information on the ecological role of mesopredators. Our study uses mesopredator exclosures to experimentally explore the role of mesopredators within the broader wildlife community by artificially reducing mesopredator populations. Because we are using exclosures (electric fences specifically designed to exclude mesopredators, without restricting target prey species), there will be no need to sacrifice mesopredators to accomplish study objectives. Effects of mesopredators on avian, gopher tortoise, and small mammal population dynamics are of primary interest. However, we are also monitoring snake and raptor populations to determine how mesopredators affect their numbers and distribution and whether they, in tum, influence the dynamics of other wildlife populations.

The Gopher Tortoise is an important component of a number of upland ecological communities throughout the southeastern U.S., but populations have experienced significant declines over the past century, largely in conjunction with the loss of longleaf pine (Pinus palustris) forests. Military installations have preserved large tracts of longleaf pine, often while implementing prescribed fires that mimic natural lightning-ignited fires (frequent low intensity fire is a necessary component of longleaf pine communities), which in turn has provided refuges for many imperiled longleaf associates, including the Gopher Tortoise. Eglin Air Force Base in the western Florida panhandle presents a unique situation in which large tracts of longleaf pine sandhill (suitable Gopher Tortoise habitat) are available, but tortoise sub-populations on base are small, and many tortoises currently inhabit treeless military testing and training ranges (test ranges) rather than typical forested sandhill. My objectives were therefore to identify factors that may have been influencing use of test ranges as habitat by gopher tortoises and that might explain observed differences in burrow densities among sites. In Chapter 1, I compared vegetation structure, composition, and burrow site selection among sites and between forested and test range vegetation types. I also attempted to identify relationships between vegetation characteristics and variation in burrow densities (a proxy for abundance within a given area) among sites. In Chapter 2, I distributed a questionnaire to other military installations throughout the southeast to identify common management techniques used to maintain testing and training areas at other tortoise-occupied military installations, as these techniques likely affect their suitability as tortoise habitat. In Chapter 3, I compared surface activity patterns of juvenile Gopher Tortoises between forested and test range vegetation types, as surface activity in these vulnerable, but important size classes may affect survival rates. I found that test ranges generally had greater herbaceous vegetation cover than forested sites (greater forage availability), were highly species diverse in terms of groundcover plants, and had herbaceous communities that shared a number of common sandhill plant species with forested sites, but also were unique in a number of ways. I also found that adult tortoises (burrow site selection) and juvenile tortoises (surface activity) may have exhibited different behaviors in novel test range vegetation types compared to individuals inhabiting more natural longleaf pine sandhill on base. However, I did not find strong evidence that current vegetation structure or composition was related to observed differences in burrow densities among sites and that other factors might have played a greater role in structuring Eglin's remnant tortoise sub-populations. Master of Science The Gopher Tortoise is an important component of a number of upland ecological communities throughout the southeastern U.S., but populations have experienced significant declines over the past century, largely in conjunction with the loss of longleaf pine (Pinus palustris) forests. Military installations have preserved large tracts of longleaf pine, often while implementing prescribed fires that mimic natural lightning-ignited fires (frequent low intensity fire is a necessary component of longleaf pine communities), which in turn has provided refuges for many imperiled longleaf associates, including the Gopher Tortoise. Eglin Air Force Base in the western Florida panhandle presents a unique situation in which large tracts of longleaf pine sandhill (suitable Gopher Tortoise habitat) are available, but tortoise sub-populations on base are small, and many tortoises currently inhabit treeless military testing and training ranges (test ranges) rather than typical forested sandhill. My objectives were therefore to identify factors that may have been influencing use of test ranges as habitat by gopher tortoises and that might explain observed differences in burrow densities among sites. In Chapter 1, I compared vegetation structure, composition, and burrow site selection among sites and between forested and test range vegetation types. I also attempted to identify relationships between vegetation characteristics and variation in burrow densities (a proxy for abundance within a given area) among sites. In Chapter 2, I distributed a questionnaire to other military installations throughout the southeast to identify common management techniques used to maintain testing and training areas at other tortoise-occupied military installations, as these techniques likely affect their suitability as tortoise habitat. In Chapter 3, I compared surface activity patterns of juvenile Gopher Tortoises between forested and test range vegetation types, as surface activity in these vulnerable, but important size classes may affect survival rates. I found that test ranges generally had greater herbaceous vegetation cover than forested sites (greater forage availability), were highly species diverse in terms of groundcover plants, and had herbaceous communities that shared a number of common sandhill plant species with forested sites, but also were unique in a number of ways. I also found that adult tortoises (burrow site selection) and juvenile tortoises (surface activity) may have exhibited different behaviors in novel test range vegetation types compared to individuals inhabiting more natural longleaf pine sandhill on base. However, I did not find strong evidence that current vegetation structure or composition was related to observed differences in burrow densities among sites and that other factors might have played a greater role in structuring Eglin’s remnant tortoise sub-populations.