Occupancy modeling of ruffed grouse in the Black Hills National Forest

Ruffed grouse (Bonasa umbellus) are a popular game bird and the management indicator species for quaking aspen (Populus tremuloides) in the Black Hills National Forest (BHNF), which requires development of a robust monitoring protocol to evaluate trends in ruffed grouse populations. We used roadside drumming surveys in spring 2007 and 2008 to estimate ruffed grouse occupancy and detection probabilities in the BHNF while simultaneously assessing the influence of sampling and site covariates on these processes. Ruffed grouse occupancy estimates were constant between spring 2007 and 2008 (Ψ = 0.12, SE = 0.03) and were positively influenced by the amount of aspen surrounding the site. Detection probability estimates were constant between spring 2007 and 2008 (p = 0.27, SE = 0.06) and were influenced by survey date in a quadratic form and negatively influenced by wind speed and time of the survey. Collectively, our results demonstrated that ruffed grouse occupancy and detection probabilities in the BHNF were low. Occupancy could be increased by increasing the extent of aspen. To improve monitoring efficiency and maximize probability of detecting ruffed grouse, ruffed grouse monitoring should be conducted during the peak of drumming (mid-May), during favorable weather conditions such as low wind speeds and little precipitation, and during early morning, near sunrise. © 2010 The Wildlife Society.     

Evaluating spatially explicit viability of a declining ruffed grouse population

Species associated with early successional habitats have experienced dramatic declines in the eastern United States as a result of land use changes and human disruption of natural disturbance regimes. Consequently, active management is required to create early successional habitat and promote plant and animal communities that depend on periodic forest disturbance. Ruffed grouse (Bonasa umbellus) depend on recently disturbed forest habitat, and have experienced dramatic declines over the last half-century. Although ruffed grouse are extensively studied, little effort has been made to link population dynamics with habitat management at landscape scales. We used stochastic, spatially explicit population models that combined landscape conditions derived from a Geographic Information System with demographic data, and applied the model to a declining ruffed grouse population in Rhode Island, USA. We identified vital rates that influence ruffed grouse population dynamics using baseline models constructed with current demographic rates and landscape conditions, and assessed the effect of landscape-scale forest management alternatives on population persistence by running multiple management simulations. Baseline models typically predicted population decline, and we concluded that vital rates (survival and recruitment) had a greater influence on population persistence than did dispersal capability, carrying capacity, or initial population size. Management simulations predicted greater population persistence under a scenario where high-quality habitat was provided in fewer large blocks as opposed to many small blocks, and the rate at which we allowed ruffed grouse to colonize newly created habitat had a substantial impact on management success. Populations of ruffed grouse in the eastern United States are likely to continue to decline given current disturbance regimes, and our work provides a link between ruffed grouse demography and landscape-scale habitat conditions to support management decisions. © 2011 The Wildlife Society.     

花尾榛鸡的非对称性比和成体存活率

1999至2002年,在法国东南部的阿尔卑斯山,通过无线电追踪方法研究了花尾榛鸡的性比问题。首先,我们通过直接观测无线电标记雄性的配对比例,在消除可能的捕捉误差后,发现繁殖种群性比为1．26（即未配对的雄性占21％）。然后,我们估计了标记个体的存活率和繁殖成功率。在假设窝扩散时幼体的性比平衡的前提下,通过两性和两个年龄组（幼体,〈10月龄的个体;成体〉10月龄的个体）的确定性统计模型,得到的理论性比为1．22（即未配对的雄性占18％）,这一结果与实际观测的性比十分接近。我们认为,雌性死亡率高导致的两性存活率差异可以解释雄性性比偏高现象。我们进而讨论了花尾榛鸡整个分布区内居间强度的非对称性比的适应意义,以及在衰退的花尾榛鸡种群中雌性数量极端不足的后果[动物学报52（4）：655—662,2006]。     

The cost of dispersal: predation as a function of movement and site familiarity in ruffed grouse

Ecologists often assume that dispersing individuals experienceincreased predation risk owing to increased exposure to predatorswhile moving. To test the hypothesis that predation risk isa function of movement distance or rate of movement, we usedradio-telemetry data collected from 193 ruffed grouse (Bonasaumbellus) during 1996–1999 in southeastern Ohio. Cox'sproportional hazards model was used to examine whether the riskof predation was affected by the rate of movement and site familiarity.We found evidence indicating that increased movement rates mayincrease the risk of predation for adult birds but not juveniles.We also found juvenile and adult birds inhabiting unfamiliarspace were consistently at a much higher risk of predation (threeto 7.5 times greater) than those in familiar space. Our resultsindicate that although movement itself may have some effecton the risk of being preyed upon, moving through unfamiliarspace has a much greater effect on risk for ruffed grouse. Thissupports the hypothesis that increased predation risk may bean important cost of dispersal for birds.     

Secondary sex ratios by maternal rank,parity, and age in captive rhesus macaques (Macaca mulatta)

Analysis of 645 conceptions by captive rhesus macaques (Macaca mulatta) with known reproductive histories indicated that maternal age and parity had little effect on the sex of progeny. There was, however, a slight indication that high-ranking females produced a higher proportion of daughters and relatively fewer sons than did low-ranking females. These results provide only weak support for the “advantaged daughter” hypothesis suggested by three previous studies of cercopithecine monkeys, and therefore they further confound the conflicting results for macaques and baboons in general.     

Dioecy and the evolution of sex ratios in ants

Split sex ratios, when some colonies produce only male and others only female reproductives, is a common feature of social insects, especially ants. The most widely accepted explanation for split sex ratios was proposed by Boomsma and Grafen, and is driven by conflicts of interest among colonies that vary in relatedness. The predictions of the Boomsma–Grafen model have been confirmed in many cases, but contradicted in several others. We adapt a model for the evolution of dioecy in plants to make predictions about the evolution of split sex ratios in social insects. Reproductive specialization results from the instability of the evolutionarily stable strategy (ESS) sex ratio, and is independent of variation in relatedness. We test predictions of the model with data from a long-term study of harvester ants, and show that it correctly predicts the intermediate sex ratios we observe in our study species. The dioecy model provides a comprehensive framework for sex allocation that is based on the pay-offs to the colony via production of males and females, and is independent of the genetic variation among colonies. However, in populations where the conditions for the Boomsma–Grafen model hold, kin selection will still lead to an association between sex ratio and relatedness.     

Sex ratios in blue whales from conception onward: effects of space,time, and body size

Deviations from equal sex ratios in mammals can reveal insights into sex-specific growth, survival, movements, and behavior. We assessed blue whale (Balaenoptera musculus) sex ratios based on 21,542 fetal and 311,901 whaling records, finding that males were slightly but significantly more common than females (51.3% fetal, 52.1% postnatal). Antarctic catches shifted from 52.4% male before 1951 to 48.0% male thereafter, even though larger females were preferentially targeted by whalers and should have declined. The southernmost land stations caught more males than those in southern Africa, and at land stations, sex ratios shifted subtly over the course of a year. Pelagic catches demonstrated spatial structure in sex ratios, including more males being caught in the Ross Sea. In utero, the smallest females were often misidentified as males, and there was some evidence for higher prenatal male mortality. Once born, medium-sized blue whales within each region were more often male, while the longest were nearly all female; explained entirely by females growing faster and reaching longer sizes. Overall, though, sex ratios are remarkably close to equality across time, space, and length; with any deviations best explained by faster female growth and size-selective whaling.     

Spatially explicit models of seasonal habitat for greater sage‐grouse at broad spatial scales: Informing areas for management in Nevada and northeastern California

Defining boundaries of species' habitat across broad spatial scales is often necessary for management decisions, and yet challenging for species that demonstrate differential variation in seasonal habitat use. Spatially explicit indices that incorporate temporal shifts in selection can help overcome such challenges, especially for species of high conservation concern. Greater sage‐grouse Centrocercus urophasianus (hereafter, sage‐grouse), a sagebrush obligate species inhabiting the American West, represents an important case study because sage‐grouse exhibit seasonal habitat patterns, populations are declining in most portions of their range and are central to contemporary national land use policies. Here, we modeled spatiotemporal selection patterns for telemetered sage‐grouse across multiple study sites (1,084 sage‐grouse; 30,690 locations) in the Great Basin. We developed broad‐scale spatially explicit habitat indices that elucidated space use patterns (spring, summer/fall, and winter) and accounted for regional climatic variation using previously published hydrographic boundaries. We then evaluated differences in selection/avoidance of each habitat characteristic between seasons and hydrographic regions. Most notably, sage‐grouse consistently selected areas dominated by sagebrush with few or no conifers but varied in type of sagebrush selected by season and region. Spatiotemporal variation was most apparent based on availability of water resources and herbaceous cover, where sage‐grouse strongly selected upland natural springs in xeric regions but selected larger wet meadows in mesic regions. Additionally, during the breeding period in spring, herbaceous cover was selected strongly in the mesic regions. Lastly, we expanded upon an existing joint–index framework by combining seasonal habitat indices with a probabilistic index of sage‐grouse abundance and space use to produce habitat maps useful for sage‐grouse management. These products can serve as conservation planning tools that help predict expected benefits of restoration activities, while highlighting areas most critical to sustaining sage‐grouse populations. Our joint–index framework can be applied to other species that exhibit seasonal shifts in habitat requirements to help better guide conservation actions.     

Determinants of biased sex ratios and inter-sex costs of reproduction in dioecious tropical forest trees

Estimates of the sex ratio and cost of reproduction in plant populations have implications for resource use by animals, reserve design, and mechanisms of species coexistence, but may be biased unless all potentially reproductive individuals are censused over several flowering seasons. To investigate mechanisms maintaining dioecy in tropical forest trees, we recorded the flowering activity, sexual expression, and reproductive effort of all 2209 potentially reproductive individuals within 16 species of Myristicaceae over 4 years on a large forest plot in Amazonian Ecuador. Female trees invested >10 times more biomass than males in total reproduction. Flowering sex ratios were male-biased in four species in ≥1 year, and cumulative 4-year sex ratios were male-biased in two species and for the whole family, but different mechanisms were responsible for this in different species. Annual growth rates were equivalent for both sexes, implying that females can compensate for their greater reproductive investment. There was no strict spatial segregation of the sexes, but females were more often associated with specific habitats than males. We conclude that male-biased sex ratios are not manifested uniformly even after exhaustive sampling and that the mechanisms balancing the higher cost of female reproduction are extremely variable.     

Parasitoid and inquiline attack in the galls of four alien, cynipid gall wasps: host switches and the effect on parasitoid sex ratios

1. Four alien cynipid gall wasps of the genus Andricus are established and still spreading in the British Isles. The order, according to the northerliness of their distribution boundary, is: A. corruptrix→A. quercuscalicis→A. lignicola→A. kollari. All four aliens have a sexual generation in spring on Quercus cerris (introduced to Britain) and an agamic generation in autumn on native oak species. 2. For 2 years 1994 and 1995, galls of both generations of the four alien species were sampled at eight sites from the south of England to the north of Scotland to determine the parasitoid and inquiline species that attack the new galls. The spring generations of the invading species shared a parasitoid complex of four pteromalid species. Five species of inquilines and 11 species of parasitoids emerged from the autumn galls. 3. Two colonisation events were recorded for A. lignicola and A. corruptrix. On both occasions, the spring generations were found first at the new sites, indicating that the agamic generation provides the colonisers for these invading species. After colonisation, the galls of both species were attacked by parasitoids in their first season. 4. In spring, the invading species were among the most abundant cynipids at all eight sites. By sampling the whole local community of cynipid galls, it was found that the parasitoid species attacking the spring galls of the invaders seemed to have shifted their attack to the new hosts. 5. The secondary sex ratios of the parasitoid species emerging from the sexual galls of A. quercuscalicis (the smallest of the four) showed a strong and significant male bias at all sites and in both years. Parasitoid emergence from the galls of the sexual generations of the other three species (all about equal in size) was between 60 and 70% male, and variable among sites and between years.     

Resource quality and spatial variation in sex ratios of a free-living solitary sawfly,Dineura virididorsata (Hym., Tenthredinidae)

The sex ratio in final-instar larvae of a birch-feeding, free-living solitary sawfly, Dineura virididorsata, was investigated in Finnish Lapland. The prepupal proportion of females, pooled over ten sites, was 56%, and at four individual sites the sex ratio was significantly female-biased. Larval survival from egg to prepupae did not differ between the sexes. This suggests a femalebiased primary sex ratio in the field. The sex ratio varied among the sites but not among host trees within sites. Contrary to previous results with hymenopterans, we did not find that differences in the sex ratio depended on forage quality: site-specific or tree-specific sex ratios did not correlate with the average prepupal weight. A literature search indicated that female-biased sex ratios are also common in other free-living sawflies. We are unable to explain sex ratios of Dineura virididorsata or other free-living sawflies with existing general models.     

Pattern of changes in species diversity,structure and dynamics of forest ecosystems along latitudinal gradients in East Asia

We examined effects of seasonality of climate and dominant life form (evergreen/deciduous, broad-leaf/coniferous) together with energy condition on species diversity, forest structure, forest dynamics, and productivity of forest ecosystems by comparing the patterns of changes in these ecosystem attributes along altitudinal gradients in tropical regions without seasonality and along a latitudinal gradient from tropical to temperate regions in humid East Asia. We used warmth index (temperature sum during growing season, WI) as an index of energy condition common to both altitudinal and latitudinal gradients. There were apparent differences in patterns of changes in the ecosystem attributes in relation to WI among four forest formations that were classified according to dominant life form and climatic zone (tropical/temperate). Many of the ecosystem attributes—Fishers alpha of species-diversity indices, maximum tree height and stem density, productivity [increment rate of aboveground biomass (AGB)], and population and biomass turnover rates—changed sharply with WI in tropical and temperate evergreen broad-leaved forests, but did not change linearly or changed only loosely with WI in temperate deciduous broad-leaved and evergreen coniferous forests. Values of these ecosystem attributes in temperate deciduous broad-leaved and evergreen coniferous forests were higher (stem density was lower) than those in tropical and temperate evergreen broad-leaved forests under colder conditions (WI below 100°C). Present results indicate that seasonality of climate and resultant change in dominant life form work to buffer the effects of energy reduction on ecosystem attributes along latitudinal gradients.