Effect of male age structure on reproduction in white-tailed deer

Selective harvest regimes that create female-biased sex ratios can potentially lead to delayed breeding, reduced breeding synchrony, reduced productivity, and a female-biased sex ratio of offspring. These resulting changes in breeding behavior and population dynamics have potential to adversely affect population growth. In 2002, Pennsylvania implemented harvest regulation changes that reduced deer density (increased harvest of antlerless deer) and increased the number and age of antlered deer (implemented antler point restriction regulations) that resulted in a less female-biased sex ratio. We monitored date of conception, productivity (embryos/female), and sex ratio of embryos during 1999–2006 to test if timing of breeding occurred earlier and with greater synchrony, if productivity of females increased, and if the sex ratio of offspring would shift towards more males. Deer density decreased 23% and the adult (≥1.5 yr old) sex ratio declined from 2.30 to 1.95 females/male. The ratio of ≥2.5-year-old to 1.5-year-old males shifted towards more older males (1:3.7 in 2002 to 1:1.59 in 2006) and the ≥2.5-year-old male population increased from 41,853 during 1999–2001 to 54,064 by 2006. We found no evidence of any change in the timing or variability of date of conception, productivity, or offspring sex ratio. We conclude that harvest regulation changes implemented in Pennsylvania, USA, were insufficient to affect timing of breeding or population dynamics and that efforts by managers to identify a desired sex ratio or manipulate sex ratios to achieve management goals on a statewide scale will be challenging. © 2019 The Wildlife Society.     

Sex-Age Selectivity and Correlates of Capture for Winter-Trapped White-Tailed Deer

ANDREW J. TYRE⁷ ABSTRACT Despite the common use of Clover traps to capture white-tailed deer (Odocoileus virginianus), little published information exists quantifying trap success, trap selectivity (sex-age selection), or weather correlates of trap success. We quantified these relationships using white-tailed deer data from 3 study sites in the Lower Peninsula of Michigan, USA, during winters 2001–2007. We captured 610 deer in 8,569 trap-nights; pooled capture success was 0.07 deer/trap-night, although site-year success varied from 0.021 to 0.086. We compared sex-age classes (fawn [pooled by sex], ad M, ad F) captured with sex-age classes estimated to be available on each study site during each capture season. We used generalized linear mixed modeling to construct 19 a priori models to describe probability of capture success as a function of weather covariates (daily min. temp [° C], daily snowfall [cm], daily snow depth [cm]), Julian day, site, and year. General selection patterns included fawns captured more than expected and adult males captured less than expected; adult females were generally neutrally selected. The quasi-Akaike's Information Criterion best model within our set was described by the global model without Julian day and contained all 3 weather covariates and site-year effects. Our model provided some evidence that as daily snow depth increased, probability of capture increased; the positive effect of daily snowfall on capture probability was dependent on decreasing daily minimum temperature. Our results may be used to increase efficacy of deer capture programs by researchers and managers through informed decision-making about when to allocate effort (e.g., if extreme winter weather conditions are predicted) and when to consider alternative methods (e.g., if capture of ad M is an objective).     

Use of Bait to Increase Archery Deer Harvest in an Urban–Suburban Landscape

Abstract: Hunting is the primary tool for managing white-tailed deer (Odocoileus virginianus) populations. Effectiveness of hunting in suburban areas may be reduced due to limited hunter access to small properties, firearms-discharge laws, and public safety concerns. In Connecticut, USA, hunting over bait on private land was recently legalized to increase harvest opportunities. Our objective was to assess bow-hunter willingness to use bait and effects of bait type, hunter disturbance, time spent hunting, and property size on deer-harvest potential in a suburban landscape. We mailed a prebaiting survey in February 2002 and a postbaiting survey in February 2004 to the same group of hunters. Hunters using bait were more successful and harvested more deer than hunters using no bait. Hunters using bait on small properties observed similar numbers of deer within shooting range as hunters using bait on larger properties. Hunters using bait met their venison needs, whereas hunters using no bait did not meet their needs. Resource managers should implement strategies that increase hunter success when developing urban deer-management programs for communities.     

Density of deer in relation to the prevalence of Borrelia burgdorferi s.1. in Ixodes ricinus nymphs in Rambouillet forest, France

The Rambouillet Forest, a Lyme disease-endemic area near Paris, France, was surveyed from September 1994 to October 1995 to determine the risk periods and zones for humans. Firstly, during the period of Ixodes ricinus activity, abundance of nymphs is greater in spring than in autumn. Secondly, we observed significant variation in nymphal abundance between zones according to the density of cervids. The polymerase chain reaction (PCR) was used to detect DNA of Borrelia burgdorferi sensu lato in 461 unfed nymphs. DNA was detected in 38 nymphs (8.2%). By genospecific PCR based on the OspA gene, we detected the three pathogenic spirochetes with occurrences of 10.3, 31.1 and 58.6 for B. burgdorferi s.s., Borrelia garinii and Borrelia afzelii, respectively, indicating that B. afzelii is probably the main Borrelia species in the Rambouillet Forest. Finally, 11.5% of positive nymphs exhibited a double infection. Infection rates of I. ricinus nymphs by B. burgdorferi s.l. were not significantly different throughout the year for a given area, indicating that the risk periods of acquiring Lyme disease are mainly linked to nymph activity and correspond to spring and autumn. Likewise infection rates of nymphs were not significantly different between zones with a high density of deer (more than 100 animals per 100 ha) and zones with lower deer density (less than 20 animals per 100 ha). In addition to the role of deer as an amplifier of tick populations, these data indicate that zones with a high density of cervids should be considered as higher risk areas. © Rapid Science Ltd. 1998     

Improved nutrition cues switch from efficiency to luxury phenotypes for a long‐lived ungulate

Cervid phenotype can be categorized as efficiency, which promotes survival but not extravagant growth, or luxury which promotes growth of large weaponry and body size. Although nutritional variation greatly influences these phenotypic forms, the potential for subspecies‐linked genetic or founder effects from restocking efforts of harvested species has not been eliminated. We measured intergenerational phenotypic change of males in response to improved nutrition in three captive‐reared populations of white‐tailed deer. Study animals were offspring of females captured from three regions displaying variation in antler and body size as well as nutritional variation. We fed all animals a high‐quality diet and measured antler and body size for two generations. We predicted that improved long‐term nutrition would cue a switch from efficiency to luxury phenotype for all populations and that regional compensation of antler and body size would occur. Improved nutrition positively influenced all measures of antler and body size; however, changes varied in magnitude. Antler size was more responsive than body size. Improved nutrition also facilitated regional compensation of antler size and partial compensation of body size. Our results show that improved long‐term nutrition cues a shift from efficiency to luxury phenotype in a long‐lived cervid with weaponry being more responsive than body size. Compensation of antler size suggests that weaponry is greatly influenced by nutrition and is not restricted by subspecies‐linked genetic or founder effects from restocking efforts related to our regional populations. Therefore, strategies to improve cervid antler and body size should include habitat management that elevates long‐term diet quality.