Cascading Effects of Hunting Disturbance on Northern Bobwhite Behavior, Physiology, and Survival

The northern bobwhite (Colinus virginianus; hereafter, bobwhite) is an important gamebird across the United States and has been in decline for several decades. As a commonly hunted prey species, the bobwhite provides an ideal study species to investigate the use of proactive and reactive antipredator behaviors in response to hunting pressure. We designed an experiment to understand how late-season hunting affects bobwhite demographics using fecal glucocorticoid (fGCM) concentrations, foraging and movement behaviors, survival, and breeding season metrics. Our results show that bobwhite responded to increased interactions with a shotgun through proactive responses. After one encounter with a discharged shotgun, bobwhite began foraging farther from supplemental feed where the risk of encountering a hunting party was the greatest (β = 0.21, 95% Bayesian credible interval [CrI]: 0.06–0.36). Bobwhite responded to increased hunting pressure, particularly late-season hunting pressure, via reactive responses through increased fecal glucocorticoid metabolite (fGCM) concentrations (β = 2.18, 95% CrI: 0.21–4.15), resulting in decreased survivorship in non-harvested individuals (β = -0.42, 95% CrI: -0.77 to -0.07) and decreased fecundity (β = -0.17, 95% CI: -0.31–0.09). These results can help inform hunting season regulations and management decisions aiding in bobwhite recovery

Maternal effects mediated by egg quality in the Yellow-legged Gull Larus michahellis in relation to laying order and embryo sex

<p>Abstract</p> <p>Background</p> <p>Maternal effects mediated by egg size and quality may profoundly affect offspring development and performance, and mothers may adjust egg traits according to environmental or social influences. In avian species, context-dependency of maternal effects may result in variation in egg composition, as well as in differential patterns of covariation among selected egg components, according to, for example, position in the laying sequence or offspring sex. We investigated variation in major classes of egg yolk components (carotenoids, vitamins and steroid hormones) in relation to egg size, position in the laying sequence and embryo sex in clutches of the Yellow-legged Gull (<it>Larus michahellis</it>). We also investigated their covariation, to highlight mutual adjustments, maternal constraints or trade-offs in egg allocation.</p> <p>Results</p> <p>Laying sequence-specific patterns of allocation emerged: concentration of carotenoids and vitamin E decreased, while concentrations of androgens increased. Vitamin A, estradiol and corticosterone did not show any change. There was no evidence of sex-specific allocation or covariation of yolk components. Concentrations of carotenoids and vitamins were positively correlated. Egg mass decreased along the laying sequence, and this decrease was negatively correlated with the mean concentrations of carotenoids in clutches, suggesting that nutritionally constrained females lay low quality clutches in terms of carotenoid content. Finally, clutches with smaller decline in antioxidants between first- and last-laid eggs had a larger increase in yolk corticosterone, suggesting that a smaller antioxidant depletion along the laying sequence may entail a cost for laying females in terms of increased stress levels.</p> <p>Conclusions</p> <p>Since some of the analyzed yolk components (e.g. testosterone and lutein) are known to exert sex-specific phenotypic effects on the progeny in this species, the lack of sex-specific egg allocation by mothers may either result from trade-offs between contrasting effects of different egg components on male and female offspring, or indicate that sex-specific traits are controlled primarily by mechanisms of sexual differentiation, including endogenous hormone production or metabolism of exogenous antioxidants, during embryonic development.</p

Livestock abundance predicts vampire bat demography, immune profiles, and bacterial infection risk

Human activities create novel food resources that can alter wildlife–pathogen interactions. If resources amplify or dampen, pathogen transmission probably depends on both host ecology and pathogen biology, but studies that measure responses to provisioning across both scales are rare. We tested these relationships with a 4-year study of 369 common vampire bats across 10 sites in Peru and Belize that differ in the abundance of livestock, an important anthropogenic food source. We quantified innate and adaptive immunity from bats and assessed infection with two common bacteria. We predicted that abundant livestock could reduce starvation and foraging effort, allowing for greater investments in immunity. Bats from high-livestock sites had higher microbicidal activity and proportions of neutrophils but lower immunoglobulin G and proportions of lymphocytes, suggesting more investment in innate relative to adaptive immunity and either greater chronic stress or pathogen exposure. This relationship was most pronounced in reproductive bats, which were also more common in high-livestock sites, suggesting feedbacks between demographic correlates of provisioning and immunity. Infection with both Bartonella and haemoplasmas were correlated with similar immune profiles, and both pathogens tended to be less prevalent in high-livestock sites, although effects were weaker for haemoplasmas. These differing responses to provisioning might therefore reflect distinct transmission processes. Predicting how provisioning alters host–pathogen interactions requires considering how both within-host processes and transmission modes respond to resource shifts

Low Gestational Weight Gain Skews Human Sex Ratios towards Females.

BACKGROUND:Human males are more vulnerable to adverse conditions than females starting early in gestation and continuing throughout life, and previous studies show that severe food restriction can influence the sex ratios of human births. It remains unclear, however, whether subtle differences in caloric intake during gestation alter survival of fetuses in a sex-specific way. I hypothesized that the ratio of male to female babies born should vary with the amount of weight gained during gestation. I predicted that women who gain low amounts of weight during gestation should produce significantly more females, and that, if gestational weight gain directly influences sex ratios, fetal losses would be more likely to be male when women gain inadequate amounts of weight during pregnancy. METHODS:I analyzed data collected from over 68 million births over 23 years to test for a relationship between gestational weight gain and natal sex ratios, as well as between gestational weight gain and sex ratios of fetal deaths at five gestational ages. RESULTS:Gestational weight gain and the proportion of male births were positively correlated; a lower proportion of males was produced by women who gained less weight and this strong pattern was exhibited in four human races. Further, sex ratios of fetal losses at 6 months of gestation were significantly male-biased when mothers had gained low amounts of weight during pregnancy, suggesting that low caloric intake during early fetal development can stimulate the loss of male fetuses. CONCLUSION:My data indicate that human sex ratios change in response to resource availability via sex-specific fetal loss, and that a pivotal time for influences on male survival is early in fetal development, at 6 months of gestation

Relationship between full-term natal sex ratios and pre-pregnancy BMI.

<p>Different capital letters indicate significant differences.</p

Relationships between gestational weight gains and sex ratios of fetal deaths.

<p>(A) Shows this relationship at 6 months (weeks 21–24), (B) at 7 months, (C) at 8 months, (D) at 9 months, and (E) at 10 months of gestational age. Each data point represents the average proportion of male births for a given weight gain calculated using data collected by the Center for Disease Control from 2003–2012. Alpha values were derived from binary logistic regression analyses.</p

The relationship between gestational weight gain and the proportion of male births.

<p>(A) This plot shows the proportion of male births for women of all races in relation to gestational weight gain. Each data point represents the average proportion of male births for a given weight gain calculated using data collected by the Center for Disease Control from 1990–2012. Also included are individual plots for individuals of American Indian (B), Asian (C), Black (D), and White (E) descent. Alpha values were derived from binary logistic regression analyses.</p

Numbers of fetal deaths that occurred at each week of gestation.

<p>Numbers of fetal deaths that occurred at each week of gestation.</p