Bronson K. Strickland

Age and regional differences in antlers and mass of white-tailed deer

Quantifying how physiographic region affects age-related physical development of white-tailed deer (Odocoileus virginianus) will aid in understanding land management and harvest regulation impacts. We analyzed 1991-98 harvest data from Mississippis Deer Management Assistance Program (DMAP) and wildlife management areas consisting of 247,051 deer from 5 physiographic regions in Mississippi. Sex, age, and region affected eviscerated body mass (P < 0.001). Age and region affected an antler size index (P < 0.001). However, significant interactions between age and regions and differences in the slopes of growth rates for body mass and an antler size index indicated these variables develop differently across the physiographic regions for each sex. Managers should use caution when grouping body mass samples for 2.5-, 3.5-, and ≥4.5-year-old deer, as changes in age composition with limited sample size could bias mass results. Soil fertility should be considered when designing age-based selective harvest programs when management goals include maximizing antler size at harvest.

Measuring Fine-Scale White-Tailed Deer Movements and Environmental Influences Using GPS Collars

Few studies have documented fine-scale movements of ungulate species, including white-tailed deer (Odocoileus virginianus), despite the advent of global positioning system (GPS) technology incorporated into tracking devices. We collected fine-scale temporal location estimates (i.e., 15 min/relocation attempt) from 17 female and 15 male white-tailed deer over 7 years and 3 seasons in Oklahoma, USA. Our objectives were to document fine-scale movements of females and males and determine effects of reproductive phase, moon phase, and short-term weather patterns on movements. Female and male movements were primarily crepuscular. Male total daily movements were 20% greater during rut (7,363m±364) than postrut (6,156m±260). Female daily movements were greatest during postparturition (3,357m±91), followed by parturition (2,902m±107), and preparturition (2,682m±121). We found moon phase had no effect on daily, nocturnal, and diurnal deer movements and fine-scale temporal weather conditions had an inconsistent influence on deer movement patterns within season. Our data suggest that hourly and daily variation in weather events have minimal impact on movements of white-tailed deer in southern latitudes. Instead, routine crepuscular movements, presumed to maximize thermoregulation and minimize predation risk, appear to be the most important factors influencing movements.

White-tailed deer forage production in managed and unmanaged pine stands and summer food plots in Mississippi

Abstract Nutritional habitat quality in unmanaged southeastern forests often is limited because a dense midstory and litter layer impede growth of high-quality, shade-intolerant forage species. Management actions often are designed to improve the quantity of natural forages and to supplement natural forages with agronomic plantings. We evaluated the use of a selective herbicide, prescribed fire, and fertilizer to improve forage production for white-tailed deer (Odocoileus virginianus) in naturally regenerated, mature loblolly pine (Pinus taeda) stands in north-central Mississippi, treated during 1998–1999. We compared nutritional quality and production of selected forages in treated plots (n = 4) and untreated plots (n = 4) during years 2 and 3 post-treatment. We also measured quality and production of cowpeas (Vigna unguiculata) produced in food plots (n = 4). Treatment plots produced an average of 435 kg/ha of leaf biomass and 34 kg/ha of digestible protein; untreated plots averaged 119 ka/ha of leaf biomass and 7 kg/ha of digestible protein. Cowpea food plots produced 545 kg/ha of leaf biomass and 110 kg/ha of digestible protein. Carrying-capacity estimates (deer-days/ha) increased from 7 in untreated plots to 268 in treated plots. Extrapolated over a 10-year economic planning horizon, the cost of producing digestible protein was

Influence of Landscape Composition and Structure on Antler Size of White-Tailed Deer

8/kg for treated plots and

Soil Region Effects on White-tailed Deer Forage Protein Content

15/kg for cowpea food plots. Vegetation treatments as described can cost-effectively produce high-quality, natural deer forages.

Soils and forage quality as predictors of white-tailed deer Odocoileus virginianus morphometrics

Abstract Cause for spatial variation in phenotypic quality of white-tailed deer (Odocoileus virginianus) populations is of great interest to wildlife managers. Relating phenotypic variation of populations to large-scale land-use patterns may provide insight into why populations exhibit spatial variation and elucidate how management can influence population phenotype. We used an information-theoretic approach to relate average antler size of 203 deer populations to composition and structure of the habitat occupied by those populations. We used interspersion, edge, and diversity indices to represent habitat structure and percentage of area in vegetation types to represent habitat composition. Landscape composition was a better predictor of deer population antler size than was landscape structure. Percentages of the management unit in agriculture, pasture, and pine forest were variables commonly found in the region-specific set of best models. Model-averaged estimates of agriculture and pasture parameters were always positive and estimates of pine forest parameters were always negative, which suggests that land-use types that promote growth of early successional herbaceous plants will positively influence antler size and, most likely, body growth and reproduction of white-tailed deer populations. Conversely, our findings suggest landscapes dominated by pine forests did not provide optimal amounts of quality forages for white-tailed deer. Pine forest effects should be mitigated using a combination of increased harvest to lower deer density and silvicultural practices like thinning, prescribed burning, and selective herbicide applications that stimulate growth of high-quality forages beneath the forest canopy to improve deer phenotypic quality.

Condensed Tannins' Effect on White-Tailed Deer Forage Digestibility in Mississippi

Abstract Body mass and antler development of Odocoileus virginianus (White-tailed Deer) vary by soil resource region in Mississippi, but a causative link from soil to deer morphology has not been established. We investigated crude protein (CP) content of 8 important deer forages in 5 soil-resource regions to determine if regional differences in available nutrition could potentially explain some variation in morphometrics. Crude protein levels of a species composite and all but 1 individual forage species decreased from spring to summer. Every species exhibited regional differences in spring, and only 1 species did not vary by region in summer. Composite CP also differed by region. Differences in potential nutritional planes among regions may be substantial enough to impact lactation success, fawn recruitment, and body growth. Directly sampling seasonal diet quality among regions and comparing nutritional planes among deer herds of different densities may further explain regional morphometric differences.

Variation in mass and lactation among cohorts of white-tailed deer Odocoileus virginianus

Abstract Biologists tasked with managing cervids could benefit from models predicting physical characteristics. Differences in white-tailed deer Odocoileus virginianus morphometrics across soil resource areas in Mississippi, USA, provide opportunity to test the predictive capacity of soil chemical and forage quality variables. Using principal components analysis (PCA), we modeled variation in body mass and antler score of ≥ 1.5-year-old male deer against seven soil chemical variables and 12 forage quality variables to elucidate potential nutritional factors corresponding with physical variation among 21 deer populations. We developed separate sets of models at the levels of state and soil resource area (Delta, Thin Loess and Lower Coastal Plain) and compared statewide models with general linear models (GLM) that related deer morphometrics to nominal classification variables representing the three soil resource areas. PCA distinguished a gradient of increasing soil fertility and forage quality that explained 58% of body mass and 52% of antler score variation statewide. However, the GLM using soil resource area as the explanatory variable explained 78 and 61%, respectively, indicating that management models should use soil resource area to designate areas with broadly similar nutritional planes. Within soil resource areas, the region with the greatest soil fertility and forage quality (Delta) did not model successfully for either body mass or antler score. The Thin Loess was successfully modeled for antler score, but only the Lower Coastal Plain, which had the lowest level of soil and forage quality, was successfully modeled for both morphometric variables. The Delta may have represented an area with habitat quality sufficiently high to render small variations non-influential. In contrast, the generally poorer soil quality of Thin Loess and Lower Coastal Plain soils and forages may act as a limiting factor on physical expression, which allowed some response to relatively small fluctuations in range quality. The potential utility of soil and forage metrics within soil resource areas to estimate deer physical qualities appears to be primarily for fine-tuning estimates largely determined by factors such as density and land use.

Reproductive Characteristics of White-tailed Deer in Mississippi

Abstract Condensed tannins (CT) can reduce digestibility of forages for white-tailed deer (Odocoileus virginianus), potentially confounding estimates of diet quality and nutritional carrying capacity. We collected 143 spring and 142 summer samples of 8 important deer forage species from 22 properties in Mississippi, USA, and tested for CT content using a modified butanol-HCl assay. Three species (partridge pea [Chamaecrista fasciculata], southern dewberry [Rubus trivialis], and roundleaf greenbrier [Smilax rotundifolia]) contained CT, ranging from 0.11% to 6.46% dry weight. Summer CT concentration was greater than in spring for 2 species. We ranked soil samples from least to most fertile using 8 chemical characteristics and found a positive correlation between fertility and CT concentration for 1 species and no correlation for 2 species. We tested effects of CT concentration on in vitro dry matter disappearance (IVDMD) and in vitro protein digestibility using samples of partridge pea and roundleaf greenbrier and rumen fluid from 3 free-ranging deer. Average IVDMD was reduced 1.9% for each 1% increase in CT concentration. In vitro protein digestibility was reduced 2.5% for each 1% increase in CT concentration. Assuming that our methods reflect the effects of CT on in vivo digestibility, maximum loss of available crude protein (CP) in our samples was 3.0 g/100 g dry-weight forage, and only 13 of the 112 CT-containing forage samples (12%) would have decreased available CP by >1 g/100 g dry-weight forage. Deer consuming equal portions of sampled forages would lose <1% of dietary CP to CT. Comparisons of foraging area quality using crude protein estimates should be unaffected by CT under reasonable restrictions of similar habitat types, soil fertility, and time. Given the ability of deer to forage selectively and the abundance of alternative forages in Mississippi, the potential for CT to substantially affect spring or summer diet quality of deer appears minimal.

Inconsistent association of male body mass with breeding success in captive white-tailed deer

Abstract Age-specific body mass and % lactation are indices commonly used to monitor status of cervid populations relative to carrying capacity. However, prior-year body condition and reproductive status may influence these indices and alter their interpretation. We examined variation in body mass and % lactation among cohorts of female white-tailed deer Odocoileus virginianus to determine: 1) patterns of variation among age classes, 2) if cohorts compensated in subsequent years for restricted somatic development, and 3) the relationship between body mass and % lactation within cohorts. Body mass and % lactation of young deer were more variable than for older deer, potentially making them a more sensitive indicator of population status relative to carrying capacity. The lack of correlation in body mass of cohorts across years implies that cohorts can compensate for restricted somatic development during subsequent years in the environments we studied. Body mass and % lactation were positively correlated in 1.5-year cohorts, suggesting that age of primiparity was affected by body condition. However, mean cohort body mass did not influence % lactation in older cohorts. Our data support that older cohorts (≥3 years old) have greater resiliency to changes in density or to environmental events as these cohorts demonstrated less annual variation in body mass and % lactation than did younger cohorts. Annual changes in morphometrics and fecundity of younger-aged cohorts may be the best indicator of animal density relative to carrying capacity, or of environmental events that influence carrying capacity.