Resilience and Degradation in a Tropical Wetland Overgrazed by Cattle

The Pantanal, one of the largest wetlands in the world, is highly valued for its diversity of flora and fauna, and the dynamic hydrological regime, combined with heterogeneous topography, has resulted in a mosaic of diverse habitats types in terms of species and physical structure. However, the Pantanal floodplains are also important for beef cattle production due to the abundance of forage resources. Cattle prefer grazing near water bodies because these areas have high quality forage as a result of flooding regimes (Santos et al. 2002). Many wetlands go through a wet/dry cycle that is essential to maintain their productivity and function. In drier years, wetland drawdown provides optimal conditions for a diverse range of forage species, and in these conditions cattle can graze continuously leading to pasture degradation. It is therefore essential to understand the spatial and temporal dynamics of forage production and consumption. In this study we assessed and monitored vegetation, from long-term permanent plots located at the edge of one of the pond habitats intensively grazed by cattle, in order to evaluate degradation and quantify indicators of resilience (Briske et al. 2006)

Northern Bobwhite Response to Vegetation Management and Recovery in South Texas

The northern bobwhite (Colinus virginianus; hereafter, bobwhite) requires habitat structure and composition with grass cover for nesting, predator avoidance, and thermal refuge and forb cover for feeding on phytophagous arthropods and seeds. During the past 2 decades, many land managers with interest in promoting quail hunting opportunities have reduced or completely eliminated livestock across South Texas, USA, rangelands. Resting the land from grazing allows vegetation—especially grasses and forbs—to recover and thus provide nesting and foraging habitat for bobwhite and other birds. How bobwhite respond to postgrazing vegetation recovery is of keen interest to rangeland quail managers, but this topic is poorly known because case histories with quantitative data are lacking. Our objective was to investigate how bobwhite respond to the vegetation changes following removal of cattle grazing. Our study was conducted on a private ranch in Jim Hogg County, Texas and involved 3 different categories of postgrazing recovery and management: 1 area at 15 years post-cattle grazing where the landscape has been brush-sculpted and is actively managed since removal of cattle, 1 area at 3 years post-grazing with a previous stocking density of 7 ha/animal unit (high stocking density), and 1 area at 3 years post-grazing with a previous stocking density of 14 ha/animal unit (moderate stocking density). We trapped, radio-marked, and located bobwhites from March to September during 2015–2016 on the 3 comparative units. We estimated nest survival, adult breeding-season survival, home range size, and early winter density. We hypothesized that the 15-year postgrazing site would have higher early winter density, higher adult breeding season survival, and higher nest survival along with smaller mean home range size compared to the 2 more recently grazed sites. On average, the probability of a nest surviving the 23-day incubation period was highest on the 15-year postgrazing site at 0.61 ± 0.12 (mean nest survival ± standard error), with estimates of 0.32 ± 0.12 on the 3-year moderate postgrazing site and 0.33 ± 0.12 on the 3-year high postgrazing site. Adult breeding season survival did not differ among the 3 sites, and was instead influenced mostly by month within the season, probably a result of summer heat. An adult bobwhite had a 0.48 ± 0.04 probability of surviving the breeding season. Early winter density, after summer and fall production was complete, increased on all sites from 2015 to 2016 and was consistently highest on the 15-year postgrazing site. Home range sizes on the 15-year and 3-year moderate postgrazing sites were significantly larger than on the 3-year high postgrazing site. Additionally, landscape features around nest sites suggest lingering differences among the sites, supporting higher nest survival on the 15-year postgrazing site. These findings suggest that in South Texas, bobwhite populations can attain densities of approximately 2.0–2.9 birds/ha within 5 years after removal or reduction of cattle, given adequate rainfall

Invasive Wild pigs as primary nest predators for Wild turkeys

Depredation of wild turkey (Meleagris gallopavo) nests is a leading cause of reduced recruitment for the recovering and iconic game species. invasive wild pigs (Sus scrofa) are known to depredate nests, and have been expanding throughout the distributed range of wild turkeys in north America. We sought to gain better insight on the magnitude of wild pigs depredating wild turkey nests. We constructed simulated wild turkey nests throughout the home ranges of 20 GPS-collared wild pigs to evaluate nest depredation relative to three periods within the nesting season (i.e., early, peak, and late) and two nest densities (moderate = 12.5-25 nests/km2, high = 25-50 nests/km2) in south-central Texas, USA during March–June 2016. Overall, the estimated probability of nest depredation by wild pigs was 0.3, equivalent to native species of nest predators in the study area (e.g., gray fox [Urocyon cinereoargenteus], raccoon [Procyon lotor], and coyote [Canis latrans]). female wild pigs exhibited a constant rate of depredation regardless of nesting period or density of nests. However, male wild pigs increased their rate of depredation in areas with higher nest densities. Management efforts should remove wild pigs to reduce nest failure in wild turkey populations especially where recruitment is low

Distance Sampling to Assess Post-Grazing Northern Bobwhite Recovery in South Texas

Northern bobwhite (Colinus virginianus) require habitat structure with substantial grass cover for nesting, predator avoidance, and thermal refuge. During the past 2 decades, many land managers have reduced or completely eliminated livestock across South Texas rangelands with the goal of improving bobwhite habitat. How bobwhites respond to post-grazing habitat recovery is unknown. Our objective is to investigate how bobwhites respond to the vegetative changes following removal of grazing. Our study is being conducted on a private ranch in Jim Hogg County, Texas and involves 3 different areas of post-grazing habitat recovery: a 1,246 ha area rested from grazing for 15 years; a 1,133 ha area rested 3 years from high grazing (7 ha/AU); and a 1,254 ha area rested 3 years from moderate grazing (14 ha/AU). Distance sampling surveys will be conducted on the 3 areas during December 2015 and 2016. Transects will be placed 400 m apart spanning all 3 study. Data collected during these surveys will be used to estimate bobwhite density on the 3 study areas and will be compared between sites and years. We hypothesize that the 15 years post-grazing area will have higher and more evenly distributed bobwhite density than the 3 years post-grazing at high intensity or medium intensity area

Evaluating Rangeland\u27s Grazing Capacity for Livestock and Wild Herbivores Using the Delta Diet Tool and GIS Technology

Rangelands are dynamic and complex systems requiring appropriate adaptive decision-making to calculate grazing capacity integrating livestock and herbivore wildlife. This work describes the development and application of an integrated framework using the microhistological analysis (DeltaDiet tool) to identify key forage used by different herbivores from the same area associated with GIS technology to mapping landscape containing forage productivity and quality information. This study was conducted in a management unit, representative of the Nhecolândia sub-region landscape, Pantanal. During the dry period, representative fecal samples were collected from cows, capybaras and deer grazing in the same management unit for diet analysis, using the DeltaDiet tool. A field survey was conducted to assess key forage composition and utilization degree of the pastures. Landscape units and satellite image maps were made in order to define the main pastures categories. An algorithm was used to evaluate grazing capacity for livestock and wildlife integrating all the diet and pastures information as well as information available from the literature. It was then possible to define grazing capacity for each pasture categories and quality of diet selected by different herbivores

Spatial and Temporal Analyses of Bobwhite Hunting Dynamics

A variety of factors influence the harvest of northern bobwhites (Colinus virginianus) and where that harvest occurs on a landscape. Many of these factors can be quantified and manipulated to distribute harvest pressure across time and space to meet desired spring densities. We collected spatial hunting metrics using global positioning system units on trucks and hunting dogs, along with detailed hunting logs from 211 quail hunts during the 2018–2019, 2019–2020, and 2020–2021 statewide hunting seasons in Jim Hogg County, Texas, USA. We found that hunting parties effectively covered 23.8 ± 0.3 hectares per hour, with hunts lasting 3.5 ± 0.1 hours in the morning and 1.7 ± 0.1 hours in the evening. Hunts were less productive during the early season (November–mid-December), with 13% fewer encounters per hour and 31% lower harvest per encounter. We expected daily harvest to increase with hunt velocities, but found no significant relationship with the velocity of either pointing dogs or vehicles. However, as we predicted, total hunting pressure (hunts per 50-meter × 50-meter area) decreased by 12% (range = 7–17) for every 5% increase in brush density and every 10-meter increase in the distance to the nearest access road. Our findings can assist landowners and managers in the distribution of harvest and hunting pressure across properties and hunting seasons

Evaluating the Harvest Rate Recommendation for Northern Bobwhites in South Texas

The current harvest rate recommendation for northern bobwhites (Colinus virginianus; hereafter, bobwhite) in South Texas, USA is 20% of the autumn population, including crippling loss. This recommendation is based on population simulations of empirical data. We completed the first field evaluation of the 20% harvest recommendation by comparing prehunting and posthunting bobwhite density estimates on a hunted and nonhunted site in South Texas during the 2018–2019, 2019–2020, and 2020–2021 statewide bobwhite hunting seasons in Jim Hogg County, Texas. We conducted line-transect distance sampling surveys on 4 occasions per year (early November, mid-December, late January, early March) from a helicopter platform and prescribed the 20% annual bobwhite harvest from the November density estimate. According to our bobwhite density estimates, we found that bobwhite mortality (e.g., population decline) varied seasonally between hunted ( = 54% ± 3%) and nonhunted sites ( = 46% ± 5%). Our spring density estimates on both sites (i.e., hunted vs. nonhunted) were similar through the first 2 years but diverged in 2020–2021, with bobwhite densities that were 129% higher on the nonhunted site. Comparing our annual spring density results to the means reported from population models (i.e., 100-year simulations) used to create the 20% harvest recommendation, we found that the mean spring density of the model simulations was higher than our mean field estimates on both our hunted (+59%) and nonhunted sites (+77%). We recommend a conservative approach to prescribing a bobwhite harvest in South Texas, such as using the lower 95% confidence interval of a bobwhite abundance estimate for calculating harvest prescriptions, due to variability within density estimates and bobwhite survival in semiarid ranges

Invasive Wild pigs as primary nest predators for Wild turkeys

Depredation of wild turkey (Meleagris gallopavo) nests is a leading cause of reduced recruitment for the recovering and iconic game species. invasive wild pigs (Sus scrofa) are known to depredate nests, and have been expanding throughout the distributed range of wild turkeys in north America. We sought to gain better insight on the magnitude of wild pigs depredating wild turkey nests. We constructed simulated wild turkey nests throughout the home ranges of 20 GPS-collared wild pigs to evaluate nest depredation relative to three periods within the nesting season (i.e., early, peak, and late) and two nest densities (moderate = 12.5-25 nests/km2, high = 25-50 nests/km2) in south-central Texas, USA during March–June 2016. Overall, the estimated probability of nest depredation by wild pigs was 0.3, equivalent to native species of nest predators in the study area (e.g., gray fox [Urocyon cinereoargenteus], raccoon [Procyon lotor], and coyote [Canis latrans]). female wild pigs exhibited a constant rate of depredation regardless of nesting period or density of nests. However, male wild pigs increased their rate of depredation in areas with higher nest densities. Management efforts should remove wild pigs to reduce nest failure in wild turkey populations especially where recruitment is low

Bobwhite Response to Cattle Grazing in South Texas

Range management practices to improve habitat for wildlife by reducing brush and increasing herbaceous plants, coupled with reduced stocking rates, can lead to dense stands of dominant grasses, such as four-flower trichloris (Trichloris pluriflora). This monoculture of trichloris creates dense vegetation unsuitable for northern bobwhite (Colinus virginianus; hereafter, bobwhite), reduces plant species diversity, and alters ecosystem functions. The objectives of this study are to 1) evaluate the effects of a proper cattle grazing regime to improve bobwhite habitat and 2) develop a management guide documenting how cattle grazing can be used as a tool to reduce the density and cover of dominant grasses and thereby allow higher plant species richness. The study is taking place in Duval County, Texas, USA, between 2 pastures with a combined area of 2,500 ha. One pasture serves as the control (1,337 ha) while the other (1,109 ha) is grazed to maintain a stubble height of 30–40 cm. We placed 10 grazing exclosures and 10 25-m transects within each treatment to determine botanical composition and cover. Double sampling is conducted monthly to determine forage standing crop. Forage standing crop, plant species richness, total ground cover, and forage utilization will be estimated. We hypothesize that 1) the grazed pasture will contain more bobwhites than the nongrazed pasture, 2) plant species richness will be greater in the grazed pasture, and 3) grazing will reduce the cover of trichloris. In 2020, plant species richness varied among sampling periods and was recorded as 7.5 species/transect and 4.8 species/transect higher in the nongrazed control compared to the grazed pasture in June and August, respectively. After the end of the first year of grazing, however, there was no statistical difference in plant species richness between the 2 pastures, a result that does not coincide with our second hypothesis. Litter cover did not vary among sampling periods in the nongrazed pasture but changed in the grazed pasture. Litter cover was 9.4%, 14.3%, 14.6%, and 8.9% higher in the grazed pasture than in the nongrazed pasture in May, August, September, and December 2020, respectively. Bare ground cover changed throughout sampling periods in the nongrazed and grazed pastures. Bare ground cover was 22%, 18%, and 22% higher in the grazed pasture than in the nongrazed pasture in May, September, and December 2020, respectively. Trichloris cover did not change throughout the sampling period in the grazed pasture but varied in the nongrazed pasture. Trichloris cover was 31%, 20%, 37.5%, and 35.3% higher in the nongrazed pasture than in the grazed pasture in May, August, September, and December 2020, respectively; these results support our third hypothesis. We began the cattle grazing in May 2020 with a herd of 228 mother cows placed in the grazing treatment. After 109 days of grazing, the pasture reached the target stubble height and the herd was removed. In 2021 we began grazing in June with a herd of 337 stocker calves. Vegetation growth outpaced what the calves could eat, so we removed them after 56 days and added 300 bred cows. These mother cows grazed for another 96 days until the current utilization rate was met. We completed aerial surveys for both 2020 and 2021, and the results indicate that bobwhite density on the grazed pasture was about 80% higher in 2020 and 25% higher in 2021 compared to the nongrazed pasture. These findings are consistent with our first hypothesis. In theory, by reducing the trichloris cover and increasing bare ground, we are creating more usable space for bobwhites; consequently, we are recording more bobwhites in the grazed pasture. The results are preliminary, but our study has the potential to shed light on bobwhite responses to proper cattle grazing and in turn to inform decisions about managing bobwhite habitat across South Texas

Montezuma Quail in the Edwards Plateau of Texas: Detection, Occurrence, and Habitat

Montezuma quail (Cyrtonyx montezumae) were historically found throughout nearly every county in the Edwards Plateau region of Texas, USA. Over the last century, shifting land use, reduction of fire on the landscape, and the subsequent encroachment of woody vegetation have constricted the distribution of Montezuma quail to a few counties in the southern portion of the Edwards Plateau. A renewed interest in management for Montezuma quail over the last decade has been met with a lack of information regarding their habitat requirements in this region. This lack of general information and increased sightings of this elusive species in areas where Ashe’s juniper (Juniperus ashei) had been removed led to the initiation of this study to identify detection and site use. During April–August of 2015 and 2016, biweekly call-back surveys were conducted at 60 randomly stratified locations distributed across 9 properties in Edwards and Kinney counties, Texas. During each survey, weather conditions were recorded. Additionally, vegetation at each of the 60 survey locations was quantified. Montezuma quail were detected at 46% (28 of 60) of the survey locations during 6.7% of the total site visits during 2015 and 2016. Detection of Montezuma quail during call-back surveys was mostly explained by temperature. When temperatures exceeded 25 °C, probability of detection dropped below 70%. Site use by Montezuma quail was best explained by bunchgrass density as probability of site use exceeded 50% when bunchgrass density exceeded 0.63 plant/m2. Future researchers may be more successful searching for Montezuma quail with an understanding of the environmental conditions under which they are most detectable. Furthermore, since relatively dense stands of bunchgrass were associated with site occupancy, this metric gives managers a management target to shoot for when restoring Montezuma quail habitat in the region