Context Documenting cause-specific mortality and deriving survival estimates for a population are both vital to understanding potential restrictions to population growth. Survival varies among populations of the same species and depends on several factors, including climatic events, density-dependent and density-independent factors, observed predator composition and whether recreational hunting occurs. Therefore, understanding factors affecting adult survival and estimating survival rates at biologically important times will help refine management of these populations. Aims We aimed to assess cause-specific mortality, estimate survival rates, and determine at what part of the winter (January to April) most mortalities occurred for female white-tailed deer located in the Northern Great Plains region of the USA. Methods We captured 165 adult female white-tailed deer (Odocoileus virginianus) located in western North Dakota and north-western South Dakota, USA, during the winters of 2014 and 2015. We fitted individuals with Very High Frequency (VHF) radio-collars and located them 1–3 times per week to monitor survival. We investigated all mortalities to establish proximate cause of death. Key Results Survival was lowest during our Hunt time period (S=0.93), although hunter harvest was not the leading cause of mortality. Predation was the greatest source of mortality, particularly during our Post-hunt time period. Additionally, almost 90% of mortalities occurring during the Post-hunt time period happened during late winter before spring green up. Conclusions and Implications Predation was the main source of mortality for adult females in our study, with coyotes (Canis latrans) being the sole predator capable of depredation in our study area. Predation by coyotes may indicate that potential factors, including winter severity and nutritional restrictions, have decreased female body condition, making individuals more susceptible to predation. Although we report relatively high survival, managers should consider the possibility that coyotes may impact adult populations, particularly in regions where other large-sized predators occur, or in regions where coyotes are newly established. Managers should also acknowledge that overwinter density estimates may need to be adjusted during severe winters to account for mortalities that occur after population surveys are conducted.

Habitat availability can affect important life-history traits such as survival; however, little information exists on how microhabitat characteristics found at parturition sites selected by dams and bed sites selected by their offspring differ from the surrounding area and from each other. Therefore, we assessed how vegetation affected maternal parturition and offspring bed site selection for white-tailed deer (Odocoileus virginianus) in the Northern Great Plains. Dams selected for sites with decreased vegetation height, potentially improving their visibility, which may increase their ability to escape approaching predators. Conversely, there was no variation between vegetative characteristics at neonate bed sites and their associated random sites, indicating grasslands provide adequate concealment for neonates. Dams possess the ability to flee from approaching predators, thus increasing the importance of visibility while giving birth. Conversely, neonates depend on fear bradycardia as their main antipredator defense, so concealment is more important. Our results suggest that vegetation structure is an important characteristic to white-tailed deer as habitat needs vary between adults and neonates.

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 if 3- and 6-month survival estimates varied by capture method while simultaneously assessing if capture method affected model selection and interpretation of ecological covariates for white-tailed deer neonates captured from three study sites 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.

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