Neonatal White-tailed Deer Research Articles

Recursive use of home ranges and seasonal shifts in foraging behavior by a generalist carnivore.

Coyotes (Canis latrans) colonized the southeastern United States over the last century as large predators, including the red wolf (Canis rufus) and eastern cougar (Puma concolor), were extirpated from the region. As a generalist carnivore, the coyote preys on white-tailed deer (Odocoileus virginianus) and various smaller mammals, birds, and vegetation. While resource selection by coyotes has been well documented at the home-range scale, little is known about their foraging behavior, which is an important factor in thoroughly understanding influences of coyotes on prey and sympatric carnivores. We assessed third-order resource selection of coyotes at sites across Alabama, Georgia, and South Carolina during 2015-2016. Using GPS collars, we tracked 41 resident coyotes across four calendar seasons and identified suspected foraging areas using recursive analysis where individuals repeatedly returned to known locations. We found that resident coyotes selected for open landcover types throughout the year, while avoiding primary and secondary roads. Additionally, resident coyotes avoided forested landcover types while selecting for forest edges except from April to June when they foraged within interior forest away from edges. Previous studies have documented substantive predation rates on white-tailed deer neonates by coyotes, and that fawn mortality may increase in forested landscapes away from forest edge. Our findings indicate that foraging coyotes may select forest cover types during spring where fawns are more vulnerable to predation. Additionally, there has been debate in the literature as to how coyotes obtain consistent levels of deer in their diets outside of fawning and fall hunting seasons. Our study indicates that use of road-kill carcasses by coyotes was an unlikely explanation for the presence of deer in coyote diets throughout the year, as coyotes in our study were not observed using roads during foraging excursions.

Compensatory human and predator risk trade-offs in neonatal white-tailed deer

Neonatal mortality is a primary determinant of ungulate population dynamics and occurs from multiple proximal causes, but few studies have compared relationships between risk factors and cause-specific mortality. We evaluated how landscape and physiological characteristics influenced white-tailed deer ( Odocoileus virginianus ) fawn risk from predators (American black bears [ Ursus americanus ], bobcats [ Lynx rufus ], coyotes [ Canis latrans ], and wolves [ Canis lupus ]), anthropogenic causes, and non-predation natural causes (i.e ., disease, injury, or starvation). We monitored 363 fawns and identified 166 mortalities in the Upper Peninsula of Michigan, USA during 2009–2019. Human development reduced fawn predation, particularly from coyotes, but predation was compensated by vehicle collisions. Coyote predation also was reduced in more forested areas, which was offset by increased predation from black bears, bobcats, and wolves. Smaller birth mass increased risk of non-predation natural mortality but did not influence predation or anthropogenic mortality. Our results suggest that for prey living alongside human development, the survival advantage of a “human shield” from predation can be offset by anthropogenic mortality. Birth mass relationships with mortality contradicted the hypothesis that predators select weaker individuals. We conclude that landscape attributes and fawn characteristics may interact with top-down, bottom-up, and anthropogenic processes to shape neonatal white-tailed deer mortality. Because some causes of mortality have opposing relationships with risk factors, combined mortality risk assessment may mask the processes driving specific mortality causes.

Capture method affects survival estimates and subsequent interpretation of ecological covariates for a long-lived cervid.

Understanding what variables affect ungulate neonate survival is imperative to successful conservation and management of the species. Predation is commonly cited as a cause‐specific source of mortality, and ecological covariates often influence neonate survival. However, variation in survival estimates related to capture methodology has been documented with opportunistically captured neonates generally displaying greater survival than those captured via aid of vaginal implant transmitters (VITs), likely because of increased left truncation observed in the opportunistically captured datasets. Our goal was to assess whether 3‐ and 6‐month survival estimates varied by capture method while simultaneously assessing whether capture method affected model selection and interpretation of ecological covariates for white‐tailed deer neonates captured from three study sites from 2014 to 2015 in North Dakota and South Dakota, USA. We found survival varied by capture method for 3‐month neonate survival with opportunistically captured neonates displaying up to 26% greater survival than their counterparts captured via VITs; however, this relationship was not present for 6‐month survival. We also found model selection and subsequent interpretation of ecological covariates varied when analyzing datasets comprised of neonates captured via VITs, neonates captured opportunistically, and all neonates combined regardless of capture method. When interpreting results from our VIT‐only analysis for 3‐month survival, we found survival varied by three time intervals and was lowest in the first two weeks of life. Capture method did not affect 6‐month survival, which was most influenced by total precipitation occurring during 3 – 8 weeks of a neonate's life and percent canopy cover found at a neonate's capture site. Our results support previous research that capture method must be accounted for when deriving survival estimates for ungulate neonates as it can impact derived estimates and subsequent interpretation of results.

Survival is negatively associated with glucocorticoids in a wild ungulate neonate.

It is unknown how ungulate physiological responses to environmental perturbation influence overall population demographics. Moreover, neonatal physiological responses remain poorly studied despite the importance of neonatal survival to population growth. Glucocorticoid (GC) hormones potentially facilitate critical physiological and behavioral responses to environmental perturbations. However, elevated GC concentrations over time may compromise body condition and indirectly reduce survival. We evaluated baseline salivary cortisol (CORT; a primary GC in mammals) concentrations in 19 wild neonatal white-tailed deer (Odocoileus virginianus) in a northern (NS) and southern (SS) area in Pennsylvania. After ranking survival models consisting of variables hypothesized to influence neonate survival (i.e. weight, sex), the probability of neonate survival was best explained by CORT concentrations, where elevated CORT concentrations were associated with reduced survival probability to 12 weeks of age. Cortisol concentrations were greater in the SS where predation rates and predator densities were lower. As the first evaluation of baseline CORT concentrations in an ungulate neonate to our knowledge, this is also the first study to demonstrate CORT concentrations are negatively associated with ungulate survival at any life stage. Glucocorticoid hormones could provide a framework in which to better understand susceptibility to mortality in neonatal white-tailed deer.

Theileriosis in Multiple Neonatal White-tailed Deer ( Odocoileus virginianus) in Delaware, USA.

Postmortem examination of 21 neonatal white-tailed deer ( Odocoileus virginianus) from Delaware, US identified six fawns with Theileria spp. organisms or suspected infection.

The effect of terrain and female density on survival of neonatal white-tailed deer and mule deer fawns.

Juvenile survival is a highly variable life‐history trait that is critical to population growth. Antipredator tactics, including an animal's use of its physical and social environment, are critical to juvenile survival. Here, we tested the hypothesis that habitat and social characteristics influence coyote (Canis latrans) predation on white‐tailed deer (Odocoileus virginianus) and mule deer (O. hemionus) fawns in similar ways during the neonatal period. This would contrast to winter when the habitat and social characteristics that provide the most safety for each species differ. We monitored seven cohorts of white‐tailed deer and mule deer fawns at a grassland study site in Alberta, Canada. We used logistic regression and a model selection procedure to determine how habitat characteristics, climatic conditions, and female density influenced fawn survival during the first 8 weeks of life. Fawn survival improved after springs with productive vegetation (high integrated Normalized Difference Vegetation Index values). Fawns that used steeper terrain were more likely to survive. Fawns of both species had improved survival in years with higher densities of mule deer females, but not with higher densities of white‐tailed deer females, as predicted if they benefit from protection by mule deer. Our results suggest that topographical variation is a critical resource for neonates of many ungulate species, even species like white‐tailed deer that use more gentle terrain when older. Further, our results raise the possibility that neonatal white‐tailed fawns may benefit from associating with mule deer females, which may contribute to the expansion of white‐tailed deer into areas occupied by mule deer.

Scale Dependence of Female Ungulate Reproductive Success in Relation to Nutritional Condition, Resource Selection and Multi-Predator Avoidance.

Female ungulate reproductive success is dependent on the survival of their young, and affected by maternal resource selection, predator avoidance, and nutritional condition. However, potential hierarchical effects of these factors on reproductive success are largely unknown, especially in multi-predator landscapes. We expanded on previous research of neonatal white-tailed deer (Odocoileus virginianus) daily survival within home ranges to assess if resource use, integrated risk of 4 mammalian predators, maternal nutrition, winter severity, hiding cover, or interactions among these variables best explained landscape scale variation in daily or seasonal survival during the post-partum period. We hypothesized that reproductive success would be limited greater by predation risk at coarser spatiotemporal scales, but habitat use at finer scales. An additive model of daily non-ideal resource use and maternal nutrition explained the most (69%) variation in survival; though 65% of this variation was related to maternal nutrition. Strong support of maternal nutrition across spatiotemporal scales did not fully support our hypothesis, but suggested reproductive success was related to dam behaviors directed at increasing nutritional condition. These behaviors were especially important following severe winters, when dams produced smaller fawns with less probability of survival. To increase nutritional condition and decrease wolf (Canis lupus) predation risk, dams appeared to place fawns in isolated deciduous forest patches near roads. However, this resource selection represented non-ideal resources for fawns, which had greater predation risk that led to additive mortalities beyond those related to resources alone. Although the reproductive strategy of dams resulted in greater predation of fawns from alternative predators, it likely improved the life-long reproductive success of dams, as many were late-aged (>10 years old) and could have produced multiple litters of fawns. Our study emphasizes understanding the scale-dependent hierarchy of factors limiting reproductive success is essential to providing reliable knowledge for ungulate management.

Do biological and bedsite characteristics influence survival of neonatal white-tailed deer?

Coyotes recently expanded into the eastern U.S. and potentially have caused localized white-tailed deer population declines. Research has focused on quantifying coyote predation on neonates, but little research has addressed the potential influence of bedsite characteristics on survival. In 2011 and 2012, we radiocollared 65 neonates, monitored them intensively for 16 weeks, and assigned mortality causes. We used Program MARK to estimate survival to 16 weeks and included biological covariates (i.e., sex, sibling status [whether or not it had a sibling], birth weight, and Julian date of birth). Survival to 16 weeks was 0.141 (95% CI = 0.075-0.249) and the top model included only sibling status, which indicated survival was lower for neonates that had a sibling. Predation was the leading cause of mortality (35 of 55; 64%) and coyotes were responsible for the majority of depredations (30 of 35; 86%). Additionally, we relocated neonates for the first 10 days of life and measured distance to firebreak, visual obstruction, and plant diversity at bedsites. Survival of predation to 10 days (0.726; 95% CI = 0.586-0.833) was weakly associated with plant diversity at bedsites but not related to visual obstruction. Our results indicate that neonate survival was low and coyote predation was an important source of mortality, which corroborates several recent studies from the region. Additionally, we detected only weak support for bedsite cover as a covariate to neonate survival, which indicates that mitigating effects of coyote predation on neonates may be more complicated than simply managing for increased hiding cover.

Confirmation of Coyote Predation on Adult Female White-Tailed Deer in the Southeastern United States

The recent expansion of Canis latrans (Coyote) into the eastern United States has gener- ated interest among wildlife managers because of the potential impacts on Odocoileus virginianus (White-tailed Deer) populations. Coyotes have been reported as predators of adult and neonate White-tailed Deer in some parts of their range, but recent studies in the Southeast have documented only Coyote predation on neonates. We report 4 confirmed Coyote predation events on adult female White-tailed Deer that were radiocollared, implanted with vaginal implant transmitters, monitored every 4-8 hours, and apparently healthy. Field necropsies confirmed killing-bite wounds to the up- per throat and base of the mandible, and feeding behavior on the carcasses was consistent with what has been observed for Coyotes. Further, we used swabs from bite wounds to confirm the presence of predator DNA, and the 3 carcasses that were swabbed tested positive for the presence of Coyote DNA. To our knowledge, our results represent the first scientifically documented Coyote predations on adult female White-tailed Deer in the Southeast.

Coyote removal, understory cover, and survival of white-tailed deer neonates

Predation by coyotes (Canis latrans) on white-tailed deer (Odocoileus virginianus) neonates has led to reduced recruitment in many deer populations in southeastern North America. This low recruitment combined with liberal antlerless deer harvest has resulted in declines in some deer populations, and consequently, increased interest in coyote population control. We investigated whether neonate survival increased after coyote removal, whether coyote predation on neonates was additive to other mortality sources, and whether understory vegetation density affected neonate survival. We monitored neonate survival for 4 years prior to (2006–2009) and 3 years during (2010–2012) intensive coyote removal on 3 32-km2 units on the United States Department of Energy’s Savannah River Site, South Carolina. We removed 474 coyotes (1.63 coyotes/km2 per unit per year), reducing coyote abundance by 78% from pre-removal levels. The best model (wi = 0.927) describing survival probability among 216 radio-collared neonates included a within-year quadratic time trend variable, date of birth, removal treatment, and a varying removal year effect. Under this model, survival differed between pre-treatment and removal periods and it differed among years during the removal period, being >100% greater than pre-treatment survival (0.228) during the first removal year (0.513), similar to pre-treatment survival during the second removalmore » year (0.202), and intermediate during the third removal year (0.431). Despite an initial increase, the overall effect of coyote removal on neonate survival was modest. Mortality rate attributable to coyote predation was lowest during the first removal year (0.357) when survival was greatest, but the mortality rate from all other causes did not differ between the pretreatment period and any year during removals, indicating that coyote predation acted as an additive source of mortality. Survival probability was not related to vegetation cover, either directly or in interaction with coyote abundance. When the objective is to increase the recruitment of white-tailed deer, we conclude that neither coyote control nor vegetation management appear effective. Reduction of the antlerless harvest may be necessary to meet this objective, but this harvest strategy warrants additional research in Southeastern deer populations.« less

Effects of maternal nutrition, resource use and multi-predator risk on neonatal white-tailed deer survival.

Growth of ungulate populations is typically most sensitive to survival of neonates, which in turn is influenced by maternal nutritional condition and trade-offs in resource selection and avoidance of predators. We assessed whether resource use, multi-predator risk, maternal nutritional effects, hiding cover, or interactions among these variables best explained variation in daily survival of free-ranging neonatal white-tailed deer (Odocoileus virginianus) during their post-partum period (14 May–31 Aug) in Michigan, USA. We used Cox proportional hazards mixed-effects models to assess survival related to covariates of resource use, composite predation risk of 4 mammalian predators, fawn body mass at birth, winter weather, and vegetation growth phenology. Predation, particularly from coyotes (Canis latrans), was the leading cause of mortality; however, an additive model of non-ideal resource use and maternal nutritional effects explained 71% of the variation in survival. This relationship suggested that dams selected areas where fawns had poor resources, while greater predation in these areas led to additive mortalities beyond those related to resource use alone. Also, maternal nutritional effects suggested that severe winters resulted in dams producing smaller fawns, which decreased their likelihood of survival. Fawn resource use appeared to reflect dam avoidance of lowland forests with poor forage and greater use by wolves (C. lupus), their primary predator. While this strategy led to greater fawn mortality, particularly by coyotes, it likely promoted the life-long reproductive success of dams because many reached late-age (>10 years old) and could have produced multiple generations of fawns. Studies often link resource selection and survival of ungulates, but our results suggested that multiple factors can mediate that relationship, including multi-predator risk. We emphasize the importance of identifying interactions among biological and environmental factors when assessing survival of ungulates.

Vocalization Observed in Starving White-Tailed Deer Neonates

We observed loud, frequent vocalizations by 5 Odocoileus virginianus (White-tailed Deer) neonates that ultimately died of starvation due to abandonment. We did not observe this behavior by other neonates, regardless of survival or cause of mortality. Thus, we believe that neonate vocalization could serve as a useful field indicator of abandonment. Additionally, estimates of predation rates may be inflated because they are masking high rates of undetected abandonment.

Factors Influencing Survival of White-tailed Deer Fawns in Coastal South Carolina

Abstract The social and environmental pressures exerted on white-tailed deer Odocoileus virginianus in the southeastern United States are dynamic. Understanding factors that contribute to neonatal white-tailed deer mortality is vital to population management. To determine survival rates and causes of mortality, we captured and radio-monitored neonate white-tailed deer in the coastal plain of South Carolina. Using date of birth, mass, sex, age, and year as predictor variables, we created a candidate set of survival models to evaluate which factors influenced daily survival rates. We captured and monitored 210 fawns and recorded 68 total mortalities (32.3%). We recorded few mortalities in 2006 (n = 5; 12.8%) and 2007 (n = 5; 12.5%), but we observed a significant increase in mortality in 2008 (n = 18; 37.5%), 2009 (n = 28; 53.8%), and 2010 (n = 12; 38.7%). Predation accounted for the majority of mortalities (n = 29; 42.6%). We found that male fawns were more than twice as likely to survive as females, and older fawns were more likely to succumb to predation than younger fawns. Overall survival in our study was higher than estimates recently reported in the southeastern United States. Recent increases in coyote predation have been cause for concern in some parts of the Southeast, but our results indicate that although it appeared coyote predation increased over the course of our study, predation did not reach levels that have been reported elsewhere, possibly due to predator-control activities on our study site. Close monitoring of the deer population at Brosnan Forest allowed managers to adequately adjust harvest prescriptions to maintain deer populations at the desired level despite an apparent decline in fawn survival.

Behavior and survival of white-tailed deer neonates in two suburban forest preserves

Neonatal survival influences growth of unhunted populations of suburban white-tailed deer ( Odocoileus virginianus (Zimmerman, 1780)). Understanding the interaction of habitat and survival may inform conservation efforts and studies of life history of cervids at high density. We chose two forest preserves representative of forests in suburban Chicago. We radio-marked 56 neonates (1999–2001) to investigate mortality and habitat use. Through 1 July, 21 of 29 (72%) neonates and 6 of 22 (27%) died mostly because of predation by coyotes ( Canis latrans Say, 1823). Akaike’s information criterion suggested that optimal mark–recapture models of survival contained covariates reflecting differences by preserve and timing chosen to coincide with behavioral change from hiding to accompanying the doe. Survival was lower during early parturition (0.26–0.78) relative to the latter part (0.90–0.96). Early fawns (hiders) at one site had lower survival (0.26–0.29) than fawns at the other (0.78). Lower survival associated with larger home ranges, greater movement, and reduced understory cover, suggesting that hiding cover may mediate fawn survival in the presence of predators. Our study demonstrates spatial heterogeneity in population biology of suburban deer and suggests that site-specific differences may influence neonate survival in the face of coyote predation.

Does the use of vaginal-implant transmitters affect neonate survival rate of white-tailed deer Odocoileus virginianus

We compared survival of neonate white-tailed deer Odocoileus virginianus captured using vaginal-implant transmitters (VITs) and traditional ground searches to determine if capture method affects neonate survival. During winter 2003, 14 adult female radio-collared deer were fitted with VITs to aid in the spring capture of neonates; neonates were captured using VITs (N=14) and traditional ground searches (N=7). Of the VITs, seven (50%) resulted in the location of birth sites and the capture of 14 neonates. However, seven (50%) VITs were prematurely expelled prior to parturition. Predation accounted for seven neonate mortalities, and of these, five were neonates captured using VITs. During summer 2003, survival for neonates captured using VITs one, two, and three months post capture was 0.76 (SE=0.05; N=14), 0.64 (SE=0.07; N=11) and 0.64 (SE=0.08; N=9), respectively. Neonate survival one, two and three months post capture for neonates captured using ground searches was 0.71 (SE=0.11; N=7), 0.71 (SE=0.15; N=5) and 0.71 (SE=0.15; N=5), respectively. Although 71% of neonates that died were captured <24 hours after birth using VITs, survival did not differ between capture methods. Therefore, use of VITs to capture neonate white-tailed deer did not influence neonate survival. VITs enabled us to capture neonates in dense habitats which would have been difficult to locate using traditional ground searches.

Capture of white-tailed deer fawns using thermal imaging technology

Capture of neonatal white-tailed deer (Odocoileus virginianus) often is hampered by inherent difficulties in locating study animals. A variety of techniques have been described for location and capture of fawns, including foot searches, female behavioral cues, spotlighting, and vaginal transmitter implants. However, each technique has certain limitations imposed by such factors as habitat structure or logistical difficulties. We describe a new technique for locating deer fawns in which thermal imaging technology was employed. Only 3.3 person-hours were required per fawn located and 9.4 person-hours required per fawn captured. We suggest that this technique is equally or more efficient than other reported capture techniques for neonatal white-tailed deer.

Low risk of marking-induced abandonment in free-ranging white-tailed deer neonates

Abstract Marking-induced abandonment has been suggested as the most common cause of marking-induced mortality of free-ranging, newborn ungulates in North America. However, there has been no direct study of marking-induced abandonment in free-ranging ungulates, and its relevance to neonate survival is inconclusive. We describe our capture, marking, and monitoring of white-tailed deer (Odocoileus virginianus) neonates born to radiocollared dams in north-central Minnesota over 5 springs (1997, 1999–2002), as it relates to marking-induced or natural abandonment. We assumed that all neonates dying within 4 days post-marking were possible occurrences of abandonment. We captured 89 neonates; 6 (7%) died within 4 days (4 to predation, 2 to unknown causes). We found no conclusive evidence of marking-induced abandonment. Handling had no impact on neonate survival, even though nearly 40% of neonates were handled >15 minutes. Time of marking (post-parturition) was similar among survivors and nonsurvivors; 48% of surv...

Physiological responses of neonatal white-tailed deer reflective of maternal dietary protein intake

Previously, we observed a strong correlation between immunity parameters of neonatal white-tailed deer (Odocoileus virginianus) fawns and probability of survival in an overpopulated herd. As a result, we monitored age-related changes in neonatal fawn physiology, with an emphasis on measures of passive immune transfer, to test the hypothesis that maternal protein malnutrition adversely influences the vigor and immunocompetence of newborn fawns. Body mass and physiological data were collected from 55 neonatal fawns (1–28 days old) born to captive does on either a high-protein (16%) or low-protein (6.5%) diet during the latter half of gestation through lactation (15 March – 1 September). The study was conducted over two breeding seasons (1992 and 1993), with does receiving the same diet the second year to assess diet × year interactions. We found little evidence of compromised immunocompetence of neonatal fawns born to protein-malnourished does in either year. The absence of any sign of suppressed in utero development suggested that the nutritional deficiencies of the diet regime we used may not have been chronic enough to mirror conditions that exist in the wild. Birth mass, hematology, and serum chemistries of fawns suggested that low-protein diets caused reductions in maternal nutritional status by the second year. The results of this study and those of preliminary field observations suggested that compromised immunocompetence of neonatal fawns may be manifested only during chronic malnutrition, when the protein reserves of does become depleted or insufficient.

Black bear predation of white-tailed deer neonates in the central Adirondacks

Bear predation has recently been recognized as a significant mortality factor affecting free-ranging cervid populations in North America. This report documents three probable incidents of black bear predation on neonate white-tailed deer in the central Adirondack Mountains of New York during June of 1986 and 1987. Black bear predation on free-ranging white-tailed deer has not been previously reported in the northeastern United States.

Congenital anomalies in a neonatal white-tailed deer in Alberta.

In September, 1973, a live male 2-3 day old white-tailed deer (Odocoileur virginianus) with multiple anomalies of the head and forelimbs was found near Lethbridge, Alberta. Notable gross findings inculded brachygnathia inferior, atypical incisor tooth alignment, medially folded ears, humero-radial arthrogryposis and bowing of the radius and ulna. Hematologic determinations indicated increased erythrocyte, hemoglobin and hematocrit levels. Histopathologic examination revealed mineralized spherites in the cerebellum and midbrain.