Survival of white-tailed deer neonates in Minnesota and South Dakota

Understanding the influence of intrinsic (e.g., age, birth mass, and sex) and habitat factors on survival of neonate white-tailed deer improves understanding of population ecology. During 2002–2004, we captured and radiocollared 78 neonates in eastern South Dakota and southwestern Minnesota, of which 16 died before 1 September. Predation accounted for 80% of mortality; the remaining 20% was attributed to starvation. Canids (coyotes [Canis latrans], domestic dogs) accounted for 100% of predation on neonates. We used known fate analysis in Program MARK to estimate survival rates and investigate the influence of intrinsic and habitat variables on survival. We developed 2 a priori model sets, including intrinsic variables (model set 1) and habitat variables (model set 2; forested cover, wetlands, grasslands, and croplands). For model set 1, model {S_age-interval} had the lowest AIC_c (Akaike's information criterion for small sample size) value, indicating that age at mortality (3-stage age-interval: 0–2 weeks, 2–8 weeks, and >8 weeks) best explained survival. Model set 2 indicated that habitat variables did not further influence survival in the study area; β-estimates and 95% confidence intervals for habitat variables in competing models encompassed zero; thus, we excluded these models from consideration. Overall survival rate using model {S_age-interval} was 0.87 (95% CI = 0.83–0.91); 61% of mortalities occurred at 0–2 weeks of age, 26% at 2–8 weeks of age, and 13% at >8 weeks of age. Our results indicate that variables influencing survival may be area specific. Region-specific data are needed to determine influences of intrinsic and habitat variables on neonate survival before wildlife managers can determine which habitat management activities influence neonate populations. © 2011 The Wildlife Society     

Survival of white-tailed deer fawns on Marine Corps Base Quantico

Some jurisdictions in the eastern United States have reduced harvest of white-tailed deer (Odocoileus virginianus) because of perceived declines in recruitment and population size over the last decade. Although the restoration of American black bears (Ursus americanus) and the colonization of coyotes (Canis latrans) have increased fawn predation in some areas, limited information exists on how temporally dynamic resources and weather influence fawn survival. Therefore, we evaluated fawn survival probability, cause specific mortality, and if factors such as oak (Quercus spp.) mast abundance, winter severity, precipitation, and landscape composition influenced mortality risk on Marine Corps Base Quantico in northern Virginia, USA, from 2008 to 2019. We tracked 248 fawns outfitted with very high frequency radio-collars and predation was the leading cause of mortality (n = 42; 45%). We estimated survival to 133 days and survival pooling all years (2008–2019) was 0.50 (95% CI = 0.42–0.60). Increased annual red oak (Quercus spp.) mast abundance from the previous fall reduced mortality hazard for fawns. The longevity of our study revealed a link between fawn survival and a specific maternal resource (red oak mast) only available during gestation. Our results highlight the importance of oak mast in eastern deciduous forests and, more broadly, overwinter maternal condition on white-tailed deer recruitment.     

Large-scale climatic fluctuation and population dynamics of moose and white-tailed deer

1. Mech et al . (1987) documented cumulative, negative effects of previous winters' snow on rates of population increase in moose ( Alces alces ) and white-tailed deer ( Odocoileus virginianus ), but noted no effect of predation by wolves ( Canis lupus ). Those results were contested by Messier (1991), who analysed smoothed versions of the original abundance data and reported no effect of snow accumulation on population dynamics of either species, but strong effects of wolf predation and food competition.
2. McRoberts, Mech & Peterson (1995) contended that the conclusions reached by Messier (1991) were an artefact of the use of smoothed data. In a subsequent re-analysis of the smoothed data, Messier (1995) argued that the lack of an effect of snow after one year precluded the potential for a cumulative effect beyond one year.
3. We re-analysed original and smoothed data on dynamics of moose and white-tailed deer densities using the same methods as Mech et al . (1987) and Messier (1991), but we used a measure of global climatic fluctuation, the North Atlantic Oscillation (NAO) index. The NAO is the atmospheric process determining most interannual variation in snowfall and winter temperatures in northern latitudes, and its phases drive decadal trends in wintertime precipitation.
4. We observed that rates of increase of moose and white-tailed deer in both the original and smoothed data were influenced by global climatic fluctuation at 2- and 3-year lags, as well as by delayed density-dependent feedback and wolf predation.     

Survival of white-tailed deer fawns in the grasslands of the northern Great Plains

Environmental factors, such as forest characteristics, have been linked to fawn survival in eastern and southern white-tailed deer (Odocoileus virginianus) populations. In the Great Plains, less is known about how intrinsic and habitat factors influence fawn survival. During 2007–2009, we captured and radiocollared 81 fawns in north-central South Dakota and recorded 23 mortalities, of which 18 died before 1 September. Predation accounted for 52.2% of mortality; remaining mortality included human (hunting, vehicle, and farm accident; 26.1%) and hypothermia (21.7%). Coyotes (Canis latrans) accounted for 83.3% of predation on fawns. We used known-fate analysis in Program MARK to estimate summer (15 May–31 Aug) survival rates and investigated the influence of intrinsic and habitat variables on survival. We developed 2 a priori model sets, including intrinsic variables and a test of annual variation in survival (model set 1) and habitat variables (model set 2). Model set 1 indicated that summer survival varied among years (2007–2009); annual survival rates were 0.94 (SE = 0.06, n = 22), 0.78 (SE = 0.09, n = 27), and 0.54 (SE = 0.10, n = 32), respectively. Model set 2 indicated that survival was further influenced by patch density of cover habitats (Conservation Reserve Program [CRP]-grasslands, forested cover, and wetlands). Mean CRP-grassland and wetland patch density (no. patches/100 ha) were greater (P < 0.001) in home-range areas of surviving fawns ( = 1.81, SE = 0.10, n = 63; = 1.75, SE = 0.14, n = 63, respectively) than in home-range areas of fawns that died ( = 0.16, SE = 0.04, n = 18; = 1.28, SE = 0.10, n = 18, respectively). Mean forested cover patch density was less (P < 0.001) in home-range areas of surviving fawns ( = 0.77, SE = 0.10, n = 63) than in home-range areas of fawns that died ( = 1.49, SE = 0.21, n = 18). Our results indicate that management activities should focus on CRP-grassland and wetland habitats in order to maintain or improve fawn survival in the northern Great Plains, rather than forested cover composed primarily of tree plantings and shelterbelts. © 2012 The Wildlife Society.     

Predation by coyotes on white-tailed deer neonates in South Carolina

Coyotes (Canis latrans) are novel predators throughout the southeastern United States and their depredation of white-tailed deer (Odocoileus virginianus) neonates may explain observed declines in some deer populations in the region, but direct evidence for such a relationship is lacking. Our objective was to quantify neonate survival rates and causes of mortality at the United States Department of Energy's Savannah River Site (SRS), South Carolina to directly evaluate degree of predation in this deer population. From 2006 to 2009, we radio-monitored 91 neonates captured with the aid of vaginal implant transmitters in pregnant adult females and opportunistic searches. Overall Kaplan–Meier survival rate to 16 weeks of age was 0.230 (95% CI = 0.155–0.328), and it varied little among years. Our best-fitting model estimated survival at 0.220 (95% CI = 0.144–0.320). This model included a quadratic time trend variable (lowest survival rate during the first week of life and increasing to near 1.000 around week 10), and Julian date of birth (survival probability declining as date of birth increased). Predation by coyotes was the most frequent cause of death among the 70 monitored neonates that died, definitively accounting for 37% of all mortalities and potentially accounting for as much as 80% when also including probable coyote predation. Predation by bobcats (Felis rufus) accounted for 7% (definitive) to 9% (including probable bobcat predation) of mortalities. The level of coyote-induced mortality we observed is consistent with the low recruitment rates exhibited in the SRS deer population since establishment of coyotes at the site. If representative of recruitment rates across South Carolina, current harvest levels appear unsustainable. This understanding is consistent with the recent declining trend in the statewide deer population. The effects of coyote predation on recruitment should be considered when setting harvest goals, regardless of whether local deer population size is currently above or below desired levels, because coyotes can substantially reduce fawn recruitment. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

Land use and dispersal influence mortality in white-tailed deer

Restoring male age structure in white-tailed deer populations has become an important objective for many state agencies aimed at improving herd dynamics. Limiting mortality in the yearling (1–2 yr old) age class is a primary consideration, and regional differences in climate, habitat characteristics, hunting regulations, and hunter behavior complicate the understanding of how specific factors influence the risk of mortality. We used Cox proportional hazard modeling to determine the effects of body size, mean distance to road, dispersal behaviors, use of forested land, and use of land open to public hunting on the risk of mortality for a population of radio-collared, yearling males (n = 76) in Sussex County, Delaware, USA. Annual survival averaged 0.55 (95% CI = 0.45–0.68), with harvest accounting for 79% (26/33) of all mortalities. Measurements of body size (chest girth, shoulder height, and total length; cm) influenced dispersal probability but not dispersal distance. The best approximating model for mortality risk included a covariate for landownership, whereby mortality risk increased on public land. Among males who dispersed, longer-distance dispersal was associated with reduced mortality, which contradicts previous research describing dispersal as a high-risk behavior. The effect of landownership on mortality risk has not been previously identified, especially when regulations regarding harvest of yearling males are similar between landownership types. We observed annual survival rates of 0.69 (95% CI = 0.57–0.82) for deer apparently using private land exclusively during the hunting season, and 0.20 (95% CI = 0.11–0.48) for deer that used public land during the hunting season. Survival rates on private land were comparable to those of other regions actively managing male age structure. These results suggest survival of yearling males in the region is influenced by hunter harvest and the risks associated with dispersal may be minimal in areas where harvest pressure is low, although hunter harvest on public land may limit male age structure on a localized scale. © The Wildlife Society, 2019     

Landscape-scale habitat characteristics and neonatal white-tailed deer survival

Landscape-level habitat characteristics affect neonatal white-tailed deer (Odocoileus virginianus) survival. Little is known, however, about how changes in maternal habitat use after parturition affect neonate survival. We quantified survival rates and determined if neonate survival to 8 weeks was affected by weekly maternal habitat use in the agricultural Glaciated Plains (GP) and forest-grassland Ozark (OZ) eco-regions of Missouri, USA. We captured 127 pregnant female deer during 2015–2017, and fitted each with a global positioning system (GPS) radio-collar and vaginal implant transmitter (VIT). We captured 226 neonatal deer during 2015–2017, fitted each with an expandable radio-collar, and monitored survival status daily. We estimated weekly maternal home ranges and calculated habitat metrics within these home ranges. We used the Kaplan-Meier estimator to calculate 8-week survival estimates and Cox proportional hazards models to investigate the influence of habitat metrics on neonate survival. The 8-week survival estimates were 0.43 (95% CI = 0.35–0.54) and 0.47 (95% CI = 0.38–0.57) in the GP and OZ, respectively. Both of these survival estimates were lower than expected but particularly so in the GP because it is dominated by agricultural fields, a land cover type typically associated with high survival. Neonate survival in the GP was negatively correlated with the amount of edge and forest patch size within maternal home ranges. In the OZ, female neonate survival was positively correlated with birth mass, male neonate survival was not affected by birth mass, and survival of both sexes was negatively correlated with grassland patch density. We suspect these habitat metrics were related to predator searching efficiency and abundance. In the highly fragmented GP, predators might be able to easily search the largest cover habitat patches, whereas in the more contiguous OZ landscape, where cover habitat patch sizes were > 10 times the size of patches in the GP, large patches might be difficult for predators to search efficiently. Therefore, we recommend managers consider the larger landscape context when making habitat management decisions to increase white-tailed deer population productivity. © 2019 The Wildlife Society.     

Genetic diversity and population structure in urban white-tailed deer

Habitat fragmentation in urban areas has left many species isolated and vulnerable to loss of genetic variation. White-tailed deer (Odocoileus virginianus), however, thrive in urban areas. We compared genetic diversity and structure among deer in 2 urban metroparks with deer in a fenced reserve and with deer from an open, continuously distributed population to inform urban deer management. If urban deer maintain species' typical matrilineal genetic structure, removal of female groups may effectively reduce local abundance. However, if gene flow in urban areas is high, dispersal may impede efforts to reduce abundance. Although genetic diversity was high and mean relatedness was near zero in all locations, distributions of pairwise relatedness in urban metroparks and the fenced reserve contained greater proportions of closely and distantly related deer than the open locations, likely attributable to matrilineal structure. In addition, deer from the metroparks (approx. 65 km apart) were moderately differentiated (F_st = 0.092) indicating gene flow in urban areas may be less than in other landscapes. Our results indicate that removal of matrilineal groups may reduce local urban deer abundance without inducing immigration from surrounding areas. © The Wildlife Society, 2012     

White‐tailed deer exploit temporal refuge from multi‐predator and human risks on roads

Although most prey have multiple predator species, few studies have quantified how prey respond to the temporal niches of multiple predators which pose different levels of danger. For example, intraspecific variation in diel activity allows white‐tailed deer (Odocoileus virginianus) to reduce fawn activity overlap with coyotes (Canis latrans) but finding safe times of day may be more difficult for fawns in a multi‐predator context. We hypothesized that within a multi‐predator system, deer would allocate antipredation behavior optimally based on combined mortality risk from multiple sources, which would vary depending on fawn presence. We measured cause‐specific mortality of 777 adult (>1‐year‐old) and juvenile (1–4‐month‐old) deer and used 300 remote cameras to estimate the activity of deer, humans, and predators including American black bears (Ursus americanus), bobcats (Lynx rufus), coyotes, and wolves (Canis lupus). Predation and vehicle collisions accounted for 5.3 times greater mortality in juveniles (16% mortality from bears, coyotes, bobcats, wolves, and vehicles) compared with adults (3% mortality from coyotes, wolves, and vehicles). Deer nursery groups (i.e., ≥1 fawn present) were more diurnal than adult deer without fawns, causing fawns to have 24–38% less overlap with carnivores and 39% greater overlap with humans. Supporting our hypothesis, deer nursery groups appeared to optimize diel activity to minimize combined mortality risk. Temporal refuge for fawns was likely the result of carnivores avoiding humans, simplifying diel risk of five species into a trade‐off between diurnal humans and nocturnal carnivores. Functional redundancy among multiple predators with shared behaviors may partially explain why white‐tailed deer fawn predation rates are often similar among single‐ and multi‐predator systems.     

Habitat and weather influence body condition in white-tailed deer,Wisconsin, USA

In temperate and northern ecosystems where there are pronounced seasonal patterns in weather and available energy, there are corresponding patterns of body condition among white-tailed deer (Odocoileus virginianus). Body condition of white-tailed deer can affect survival and reproduction, which has large repercussions for state-level natural resource agencies that allocate hunting permits. In this study, we investigated how variation in winter weather, spring phenology, habitat composition, and browse quantity affected white-tailed deer body condition across a large spatial scale. Several body condition indicators (e.g., carcass mass, heart fat, antler size) were measured by hunters for 795 deer during September–December 2016–2018 in Wisconsin, USA. Winter severity in the previous year was an unreliable predictor of fall body condition of deer when winters were considered mild or moderate. The timing of spring green-up had a consistent effect on the body condition of all age and sex classes of deer. Earlier spring green-up resulted in heavier fawns and larger antlers among adult males. Region and spring green-up interacted to affect the heart fat of adult females. Earlier springs resulted in adult females in northern and central Wisconsin having a higher probability of heavy heart fat, whereas spring green-up had no effect on adult female heart fat in southern Wisconsin. Effects of habitat differed by age and sex class of deer, and by the body condition metric being evaluated, indicating that there are important physiological differences among age and sex classes of deer that are affected by the environment. Our study demonstrates that the hunting public can contribute large-scale, cost-effective, and quality data to deer monitoring and research projects. It is important that natural resource agencies be able to identify and recruit highly engaged members of the hunting public to ensure project success. The timing of spring green-up can have lasting effects on deer health that can be consistently observed the following fall, which is in contrast to the effects of winter severity that did not appear to persist when previous winters were mild or moderate. We encourage managers in northern or temperate regions to consider measures of spring green-up timing in conjunction with traditional winter severity when making deer population management decisions, such as antlerless tag allocation.