Enhanced control of sheep ticks in upland sheep flocks: repercussions for red grouse co-hosts

Sheep ticks Ixodes ricinus (Acari: Ixodidae) and tick-borne diseases cause major economic losses in both upland sheep farming and moorland shoots of red grouse Lagopus lagopus scoticus. Sheep were treated with acaricide four times between March and October and double-vaccinated against louping ill virus (LIV), instead of the conventional regime of two acaricide treatments and no vaccinations, on two moors in northern England. Enhanced treatment started at Westerdale Moor in 1995 and at Danby Moor in 2000; the latter had previously represented a spatial control site. From 1992 to 2003, grouse chick condition, tick burdens, reproductive success, shooting bags and LIV seroprevalence were measured. A total of 1297 grouse chicks from 398 broods were examined for ticks. Enhanced acaricide treatment reduced tick burdens by 90%, and LIV seroprevalence decreased in relation to the number of years since treatment began. Breeding success and post-breeding densities of grouse in the current sample area remained unrelated to acaricide treatment, tick burdens or LIV seroprevalence, but 25% and 60% more grouse were shot on Westerdale and Danby, respectively, after treatment enhancement than before. By improving shooting bags, tick management schemes help to maintain the economic viability of grouse moors, which, in turn, provide upland landscape and wildlife benefits.     

Influence of landscape and social interactions on transmission of disease in a social cervid

The mechanisms of pathogen transmission are often social behaviours. These occur at local scales and are affected by landscape-scale population structure. Host populations frequently exist in patchy and isolated environments that create a continuum of genetic and social familiarity. Such variability has an important multispatial effect on pathogen spread. We assessed elk dispersal (i.e. likelihood of interdeme pathogen transmission) through spatially explicit genetic analyses. At a landscape scale, the elk population was composed of one cluster within a southeast-to-northwest cline spanning three spatially discrete subpopulations of elk across two protected areas in Manitoba (Canada). Genetic data are consistent with spatial variability in apparent prevalence of bovine tuberculosis (TB) in elk. Given the existing population structure, between-subpopulation spread of disease because of elk dispersal is unlikely. Furthermore, to better understand the risk of spread and distribution of the TB, we used a combination of close-contact logging biotelemetry and genetic data, which highlights how social intercourse may affect pathogen transmission. Our results indicate that close-contact interaction rate and duration did not covary with genetic relatedness. Thus, direct elk-to-elk transmission of disease is unlikely to be constrained to related individuals. That social intercourse in elk is not limited to familial groups provides some evidence pathogen transmission may be density-dependent. We show that the combination of landscape-scale genetics, relatedness and local-scale social behaviours is a promising approach to understand and predict landscape-level pathogen transmission within our system and within all social ungulate systems affected by transmissible diseases.     

完达山林区森林采伐和非采伐区马鹿、狍子对冬季生境因子选择的比较

2003—2005年的冬季,在黑龙江省完达山地区的五泡林场,通过样线调查,利用逐步判别分析的方法,对冬季马鹿和狍子在森林采伐区和非采伐区生境选择的差异进行了比较研究,其结果表明,在该地区虽然两物种在生境选择上发生部分重叠,但在生境利用方式上均存在显著差异在采伐区马鹿主要利用中坡位或上坡位、半阴半阳或阳坡、人为干扰距离大于1000m、海拔相对较高、食物丰富度较高、乔木胸径较小、灌木密度较高的灌丛或杂木林生境;狍子主要利用中坡位或下坡位、阳坡、海拔相对较低、食物丰富度适中、乔木胸径较大、灌木密度较低、人为干扰距离要求不严格的杂木林或柞树林生境。在非采伐区,马鹿主要选择距人为干扰大于1000m、海拔较高、食物丰富度较高、乔木胸径较小的杂木林生境;狍子主要选择中坡位或下坡位、人为干扰距离要求不严格、海拔较低、食物丰富度较适中和乔木胸径较大的杂木林或杨-桦混交林生境。     

Female-biased dispersal under conditions of low male mating competition in a polygynous mammal

Sex-biased dispersal is a common phenomenon in birds and mammals. Competition for mates has been argued to be an important selective pressure favouring dispersal. Sexual differences in the level of intrasexual competition may produce asymmetries in the costs-benefits balance of dispersal and philopatry for males and females, which may favour male-biased dispersal in polygynous species such as most mammals. This being the case, condition-dependent dispersal predicts that male-bias should decrease if mating competition relaxes. We test this expectation for red deer, where male-biased dispersal is the norm. In southwestern Spain, red deer populations located in nonfenced hunting estates presented altered structures with sex ratio strongly biased to females and high proportion of young males. As a consequence, mate competition in these populations was lower than in other, most typical red deer populations. We found that, under such conditions of altered population structure, dispersal was female-biased rather than male-biased. Additionally, mate competition positively related to male dispersal but negatively to female dispersal. Other factors such as resource competition, age of individuals and sex ratio were not related to male or female dispersal. Males may not disperse if intrasexual competition is low and then females may disperse as a response to male philopatry. We propose hypotheses related to female mate choice to explain female dispersal under male philopatry. The shift of the sex-biased dispersal pattern along the gradient of mate competition highlights its condition-dependence as well as the interaction between male and female dispersal in the evolution of sex-biased dispersal.     

Selective culling of Iberian red deer stags (<Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis>) by selective montería in Spain

Hunting can affect animal populations not only by increasing mortality but also by introducing selection components associated with particular features of individuals. In addition to the most widespread hunting system in Spain for Iberian red deer stags (Cervus elaphus hispanicus) called montería, there are also selective monterías aimed at culling poor-trophy males in order to improve the average quality of the trophies for commercial hunt. This way of removing poor-trophy males contrasts with the most common procedure of shooting individual males by selective stalking that is used in other areas of Europe. Also, due to the hunting procedure by which most deer are shot while running chased by dogs, it is doubtful whether hunters are actually producing a selective impact on deer populations. In this paper, we compare data of males shot in commercial montería and in selective montería in Southern Spain. We found that males in selective montería were smaller in body size and in antler size than in commercial hunts, even correcting by age, although the selective effect was stronger at some ages. We discuss the implications of this practice for sustainable use and conservation.     

Bispectral Index Analysis of Opioid Immobilization of Rocky Mountain Elk

Abstract: We immobilized elk with either isoflurane to produce general anesthesia (control), 0.01 mg/kg carfentanil plus 0.1 mg/kg xylazine, or 0.25 mg/kg butorphanol plus 0.4 mg/kg azaperone plus 0.15 mg/kg medetomidine (BAM) and measured the bispectral index (BIS). The carfentanil-xylazine BIS (70.4 + 1.4) and the BAM BIS (60.2 + 1.5) were higher than the control BIS (47.2 + 4.1; P ≤ 0.001). These data indicate that opioids produce neuroleptanalgesia and not general anesthesia or sedation, which explains observed elk responses to these drugs.     

Changes in Elk Resource Selection and Distributions Associated With a Late-Season Elk Hunt

ABSTRACT Changes in resource selection associated with human predation risk may alter elk distributions and availability for harvest. We used Global Positioning System data collected from telemetered female elk (Cervus elaphus) to evaluate effects of refuges (areas where hunting was prohibited), spatial variation in hunting risk, and landscape attributes on resource selection within an established Greater Yellowstone Area, USA, winter range. We also evaluated elk distributions during and outside of a late-season hunting period. Refuge areas and landscape attributes such as habitat type and snow water equivalents (SWE) affected resource selection. Elk selection for flat grasslands increased as SWE increased, likely because these areas were windswept, leaving grasses exposed for foraging. Elk distributions differed during hunting and no-hunting periods. During the hunting period, elk shifted to privately owned refuge areas and the estimated odds of elk occupying refuge areas more than doubled. Risk-driven changes in resource selection resulted in reduced availability of elk for harvest. Elk selection for areas where hunting is prohibited presents a challenge for resource managers that use hunting as a tool for managing populations and influences grazing patterns on private ranchlands.     

Revisions of Rump Fat and Body Scoring Indices for Deer,Elk, and Moose

Abstract: Because they do not require sacrificing animals, body condition scores (BCS), thickness of rump fat (MAXFAT), and other similar predictors of body fat have advanced estimating nutritional condition of ungulates and their use has proliferated in North America in the last decade. However, initial testing of these predictors was too limited to assess their reliability among diverse habitats, ecotypes, subspecies, and populations across the continent. With data collected from mule deer (Odocoileus hemionus), elk (Cervus elaphus), and moose (Alces alces) during initial model development and data collected subsequently from free-ranging mule deer and elk herds across much of the western United States, we evaluated reliability across a broader range of conditions than were initially available. First, to more rigorously test reliability of the MAXFAT index, we evaluated its robustness across the 3 species, using an allometric scaling function to adjust for differences in animal size. We then evaluated MAXFAT, rump body condition score (rBCS), rLIVINDEX (an arithmetic combination of MAXFAT and rBCS), and our new allometrically scaled rump-fat thickness index using data from 815 free-ranging female Roosevelt and Rocky Mountain elk (C. e. roosevelti and C. e. nelsoni) from 19 populations encompassing 4 geographic regions and 250 free-ranging female mule deer from 7 populations and 2 regions. We tested for effects of subspecies, geographic region, and captive versus free-ranging existence. Rump-fat thickness, when scaled allometrically with body mass, was related to ingesta-free body fat over a 38–522-kg range of body mass (r² = 0.87; P < 0.001), indicating the technique is remarkably robust among at least the 3 cervid species of our analysis. However, we found an underscoring bias with the rBCS for elk that had >12% body fat. This bias translated into a difference between subspecies, because Rocky Mountain elk tended to be fatter than Roosevelt elk in our sample. Effects of observer error with the rBCS also existed for mule deer with moderate to high levels of body fat, and deer body size significantly affected accuracy of the MAXFAT predictor. Our analyses confirm robustness of the rump-fat index for these 3 species but highlight the potential for bias due to differences in body size and to observer error with BCS scoring. We present alternative LIVINDEX equations where potential bias from rBCS and bias due to body size are eliminated or reduced. These modifications improve the accuracy of estimating body fat for projects intended to monitor nutritional status of herds or to evaluate nutrition's influence on population demographics.     

Influence of Predator Harvest,Biological Factors,and Landscape on Elk Calf Survival in Idaho

ABSTRACT We evaluated survival of elk (Cervus elaphus) calves on 2 contrasting study areas in north-central Idaho, USA, from 1997 to 2004. Recruitment was modest (>30 calves:100 F [calves of either sex: F elk 1 yr old]) and stable on the South Fork study area and low (<20 calves:100 F) and declining on the Lochsa study area. The primary proximate cause of calf mortality on both study areas was predation by black bears (Ursus americanus) and mountain lions (Puma concolor). We experimentally manipulated populations of black bears and mountain lions on a portion of each study area. Black bear harvest (harvest density/600km²) initially doubled on the Lochsa treatment after manipulating season bag limits. Mountain lion harvest also increased by 60% but varied widely during the manipulation period. Harvest seasons were closed for black bears and mountain lions on the treatment portion of the South Fork study area. Using the Andersen—Gill formulation (A-G) of the Cox proportional hazards model, we examined effects of landscape structure, predator harvest levels, and biological factors on summer calf survival. We used Akaike's Information Criterion (AIC_c) and multimodel inference to assess some potentially useful predictive factors relative to calf survival. We generated risk ratios for both the best models and for model-averaged coefficients. Our models predicted that calf survival was influenced by biological factors, landscape surrounding calf locations, and predator harvest levels. The model that best explained mortality risk to calves on the Lochsa included black bear harvest (harvest density/600 km²), estimated birth mass of calves, and percentage of shrub cover surrounding calf locations. Incorporating a shrub X time interaction allowed us to correct for nonproportionality and detect that effect of shrub cover was only influential during the first 14 days of a calf's life. Model-averaging indicated that estimated birth mass of calves and black bear harvest were twice as important as the next variables, but age of calves at capture was also influential in calf survival. The model that best explained mortality risk to calves on the South Fork included black bear harvest, age of calves at capture, and gender of calves. Model-averaging indicated that age at capture and black bear harvest were twice as important as the next variable, forest with 33–66% canopy cover (Canopy 33–66). Risk to calves decreased when calves occupied areas with more of this forest cover type. Model-averaging also indicated that increased mountain lion harvest lowered calf mortality risk 4% for every 1-unit increase in lion harvest (harvest density/600 km²) but was lower (<25%) in importance compared to age at capture and black bear harvest. Our results suggest that levels of predator harvest, and presumably predator density, resource limitations expressed through calf birth mass, and habitat structure had substantial effects on calf survival. Our results can be generalized to other areas where managers are dealing with low calf elk recruitment. However, because factors vary spatially, a single management strategy applied in different areas will probably not have the same effect on calf survival.     

新疆塔里木马鹿沙雅种群的生境变化分析

塔里木马鹿(Cervus elaphus yarkandensis)沙雅种群主要分布在新疆维吾尔自治区沙雅县和库车县境内。为了评估该马鹿种群的生境现状、变化趋势和变化原因,通过野外实地考察,利用GIS和RS技术,分别解译了当地过去4个年份(1972～2006年)夏季的Landsat TM/ETM+遥感影像,得到了塔里木马鹿生境变化数据:①2006年的农田面积为27082.24hm2,高盖度植被面积22616.25hm2,中盖度植被面积66703.62hm2,低盖度植被面积64470.62hm2,水体面积39735.89hm2,荒漠面积63497.26hm2,沙漠面积40308.45hm2;②过去的34年间农田面积增加了89.2%(12768hm2),高盖度植被面积减少60.1%(34125hm2),中盖度植被面积增加了17.2%(9791hm2),低盖度植被面积增加了37.3%(17520hm2),水体面积减少26.6%(14429hm2),荒漠面积增加6.9%(4123hm2),沙漠面积增加12.6%(4523hm2);③高盖度植被的斑块数量增加了20.9%,平均斑块面积下降了48.3%,最大斑块指数下降了33.3%;景观丰富度并没有变化,但Shannon多样性指数和Shannon均匀度指数分别增加了2.5%;④高盖度植被面积变化分别与当地的人口数量和畜牧存栏数呈显著负相关(r=-1.000),而农田、沙漠和荒漠面积分别与当地人口数量及畜牧存栏数呈显著正相关(r=0.800,r=1.000,r=0.800)。表明塔里木马鹿沙雅种群生境的丧失及破碎化程度较为严重;生境丧失及破碎化是人类活动和自然环境变化共同作用的结果。