Stephen L. Webb

Assessing the Helicopter and Net Gun as a Capture Technique for White‐Tailed Deer

Abstract The helicopter and net gun is a technique used to capture white-tailed deer (Odocoileus virginianus) and is useful in a variety of habitat types and at various population densities with the ability to be highly selective. During capture, deer may sustain injuries or even die as a result of capture and handling, and may also be prone to capture myopathy. Therefore, our objectives were to determine 1) type and frequency of injuries sustained during the helicopter and net-gun capture, and 2) the effects of capture on survival of radiocollared deer. We captured 3,350 white-tailed deer from 1998 to 2005 using a net gun fired from a helicopter on 5 southern Texas, USA, ranches. Additionally, we captured 51 yearling males and 49 mature (≥4 yr of age) males and fitted them with radiocollars to monitor their survival. We recorded injuries and mortalities during capture and ranked the seriousness of injuries on a scale from 0 to 4. We recorded 281 injuries (8.4%) and as a result of capture, at least 206 deer had broken antlers (6.1%), 55 were injured (1.6%), and 20 were direct mortalities (0.6%). The most common antler injury was broken antler tines and the most common body injury was broken legs. Postcapture mortality rates were low (1%) for this capture method. Based on capture-related injuries, mortalities, and postcapture survival, we found the helicopter and net gun to be a safe capture technique compared to other capture techniques, particularly when conditions are favorable.

Scale of Management for Mature Male White‐Tailed Deer as Influenced by Home Range and Movements

Abstract The scale at which populations use landscapes influences ecological processes and management. We used dispersal and home-range data of 3 age groups of male white-tailed deer (Odocoileus virginianus) to determine the scale at which management will be effective. Home-range size at 5.5 years of age (182 ha ± 24.9 SE) was 56% smaller (P < 0.001) than home-range size of the same 13 males as yearlings (416 ± 59.4 ha). Percent overlap of yearling and 5.5-year-old home ranges was 62.7 ± 10.3% (n = 13). Distance between home-range centers of yearling and mature deer was 1,264.9 ± 407.4 m, including 3 deer that dispersed after 2.5 years of age. Average 95% fixed-kernel home-range size was 207.4 ± 20.4 ha and 225.7 ± 30.1 ha for all mature males in years 1 and 2 of our study, respectively. We found that properties >10,000 ha were needed to manage >50% of original yearling males found on the property, whereas properties of 4,500 ha would maintain 50% of original middle-aged (2.5–4.5 yr of age) and mature males (≥4.5 yr of age). Movements after dispersal were minimal, with deer shifting their center of activity <600 m and <350 m each year for middle-aged and mature males, respectively. These data could be used by managers developing management plans, recommending harvest rates, and interpreting harvest data of male white-tailed deer and by biologists attempting to understand ecological processes such as spread of disease.

Survival and Cause-Specific Mortality of Mature Male White-Tailed Deer

Abstract Understanding sources of male deer mortality is a prerequisite to a successful management program, especially in Texas, USA, where white-tailed deer (Odocoileus virginianus) are the most economically important game species. South Texas, USA, is one of the few areas where males reach older age classes (≥4.5 yr), in part because of intense population management. Therefore, we obtained survival rates and causes of mortality of 48 mature male deer in south Texas, USA, over 2 years. We calculated Kaplan–Meier survival estimates during 2 study years modified for a staggered-entry design and annual survival rates for one cohort of deer from 1998 to 2004 using recapture and radiotelemetry data. We documented 21 mortalities (16 harvest and 5 nonhunting mortalities). Average annual survival of the known-aged 1998 cohort was 82% with 52% of surviving to 6.5 years of age. Survival in study year 2 (0.497 ± 0.069) was less than in study year 1 (0.781 ± 0.073; P = 0.0047), largely because males had finally reached harvestable age (≥6.5 yr old). All but one non-harvest mortality occurred during the rut or postrut periods. It appears that a large percentage of males can reach mature age classes under intense population management, making them available for harvest when at peak antler size. This allows for increased economic returns on intensively managed white-tailed deer populations.

Size of Home Ranges and Movements Determine Size and Configuration of Management Units and Potential Spread of Disease in White-Tailed Deer (Odocoileus virginianus)

Abstract We modeled how variation in size of home ranges and annual movements of white-tailed deer (Odocoileus virginianus) in southern Texas altered ability to manage deer within various sizes of management units and discussed implications for spread of disease. The percentage of adult (≥3.5 years) males remaining on management units varied <4% across three sites in southern Texas. The spatial extent of spread of disease by adult males would be less than movements associated with migration or dispersal. Based on size of home ranges and movements, >98% of males would use management units of 1,000 km2 because their use of space would not result in use of adjoining management units. Migration of deer in northern latitudes resulted in 20% of the population using management units of 1,000 km2, which potentially could expose large areas (>25,000 km2) to disease because a greater percentage of deer would use adjoining management units compared to deer in southern latitudes. Our results are useful in determining size and configuration of management units, which will improve formulation of management plans, analysis of data from harvests, and prediction and control of disease.

WATER QUALITY AND SUMMER USE OF SOURCES OF WATER IN TEXAS

Abstract In southern Texas, the lack of free-standing water that results from low rainfall or poor water quality can be deleterious to wildlife. Water quality can deteriorate rapidly due to evaporation during summer in southern Texas, and high concentrations of salts in water can cause physiological distress; however, little research has addressed water quality and needs of wildlife in arid environments. Our objectives were to: 1) establish water use patterns of wildlife during summer, 2) correlate visitation rates to temperature and rainfall events, and 3) monitor water quality in earthen stock ponds and concrete troughs during summer. We recorded visits to water by 17 species of wildlife and cattle. Cattle, feral pigs (Sus scrofa), and white-tailed deer (Odocoileus virginianus) had peak watering times that differed from one another. Track surveys showed a generally negative correlation between rainfall and wildlife watering frequency. Troughs had significantly higher total dissolved solids and pH than ponds on both study sites. There was no effect of month on pH or total dissolved solids. Total dissolved solid concentrations for water sources on one study site were fair to excellent for livestock, whereas 2 sources on the other study site approached the maximum allowable limit.

Survey of Blood Parasites in Black Vultures and Turkey Vultures from South Carolina

Abstract Black Vultures (Coragyps atratus) and Turkey Vultures (Cathartes aura) are found throughout many parts of southeastern North America, but relatively little is known about the factors that may negatively impact their populations. We surveyed both species for blood parasites to learn more about factors that may influence their health. During 2000–2001, 22 Black Vultures and 11 Turkey Vultures were live-captured at the Savannah River Site in South Carolina. Two blood smears from each bird were made on microscope slides, stained, and examined at 1000× magnification. A Haemoproteus sp. was found in blood smears of one Turkey Vulture and microfilariae were detected in smears of one Black and two Turkey Vultures. We did not detect Leucocytozoon or Plasmodium in our samples, even though they have been reported in vultures from other parts of eastern North America.

Blood Parasites in Wood Storks (Mycteria americana) From the Southeastern United States

Wood storks (Mycteria americana) are endangered throughout their breeding range in the United States. Because of this, researchers have had little opportunity to thoroughly examine the continental wood stork population for endoparasites. The blood protozoan Haemoproteus crumenium has been identified from several populations of wood storks in North America. However, there have been no reports of wood storks being infected with species of Plasmodium or Leucocytozoon. During 2003, 42 nestling wood storks were captured at sites in Georgia and 27 free-ranging wood storks were captured at postbreeding dispersal sites in Mississippi and Louisiana. Two thin blood smears were made from each bird, and they were examined for parasites. Haemoproteus crumenium was found in 5 wood storks (7.2%), whereas Leucocytozoon sp., Plasmodium sp., and microfilariae were not observed. Mean intensity of H. crumenium was 4.4 ± 0.7 (SE) per 2,000 erythrocytes counted. All infected wood storks were subadult or adult and were from postbreeding dispersal sites in Mississippi.

Pseudorabies Virus and Brucella abortus from an Expanding Wild Pig (Sus scrofa) Population in Southern Oklahoma, USA

Abstract Wild pigs (Sus scrofa) are causing increasing ecologic and economic damage at a global scale. Because wild pigs can carry ≥65 diseases that affect livestock, their widespread expansion threatens native wildlife and livestock. We screened wild pigs from south-central Oklahoma, US for antibodies against Brucella abortus, pseudorabies virus (PRV), and porcine reproductive and respiratory syndrome virus (PRRS). These pathogens were chosen because they are part of eradication programs in the US and could have large economic impacts on domestic livestock if transmitted from wild animals. We tested 282 serum samples during spring 2010 (n=149) and 2011 (n=133) and found an overall exposure rate to PRV of 24.1% (n=68); PRV was detected at two of three study sites. Two wild pigs had detectable antibody to B. abortus, and one had detectable antibody to PRRS. On average, 27% of wild pigs within a sounder were positive for PRV antibody, with 44% of the sounders (16/36) having at least one positive individual. These data highlight that wild pigs could carry pathogens that affect domestic livestock. Because the US is free of these pathogens in commercial livestock operations, continued surveillance and vaccination of domestic livestock are needed. Commercial livestock producers at the wildlife-livestock interface may benefit from spatial prioritization of risk zones to facilitate strategic control efforts.

Hematozoa and a New Haemoproteid Species from Cathartidae(New World Vulture) in South Carolina

Abstract A survey of turkey vultures (Cathartes aura) in South Carolina revealed the presence of a novel haemoproteid. Haemoproteus catharti n. sp. is described from the slides developed from the blood of this vulture. The new species is a thick, halteridial form with complete margins, and is considered distinct from the other recognized haemoproteids from the diurnal raptors in shape, pigment number, parasite outline, and host-family specificity. While reviewing blood films, a series of unusual immature schizonts of Plasmodium sp. were also observed, and these are illustrated, along with another distinct haemoproteid from old slides of poor quality produced from turkey vulture blood.

SIZE AND FIDELITY OF HOME RANGES OF MALE WHITE-TAILED DEER (ODOCOILEUS VIRGINIANUS) IN SOUTHERN TEXAS

Abstract We studied size and fidelity of home ranges of adult (≥3.5 years) male white-tailed deer (Odocoileus virginianus) during 2 years in southern Texas. Size of core areas, determined using the 50% fixed-kernel method, averaged 86 ± 14 ha, whereas size of home ranges, determined using the 95% fixed-kernel method, averaged 403 ± 61 ha. Deer shifted centroids of home ranges 363 ± 45 m from year 1 to year 2. Overlap in home ranges averaged 66 ± 2% between years. These data provide additional support that home ranges of adult male white-tailed deer in southern Texas are relatively small and stable. However, the majority of home ranges are larger than most landholdings. Therefore, development of cooperatives among neighboring landowners may be necessary to effectively manage age structure of males.