Random Forest characterization of upland vegetation and management burning from aerial imagery

Aim The upland moorlands of Great Britain form distinctive landscapes of international conservation importance, comprising mosaics of heathland, acid grassland, blanket bog and bracken. Much of this landscape is managed by rotational burning to create gamebird habitat and there is concern over whether this is driving long‐term changes in upland vegetation communities. However, the inaccessibility and scale of uplands means that monitoring changes in vegetation and burning practices is difficult. We aim to overcome this problem by developing methods to classify aerial imagery into high‐resolution maps of dominant vegetation cover, including the distribution of burns on managed grouse moors. Location  Peak District National Park, England, UK. Methods Colour and infrared aerial photographs were classified into seven dominant land‐cover classes using the Random Forest ensemble machine learning algorithm. In addition, heather (Calluna vulgaris) was further differentiated into growth phases, including sites that were newly burnt. We then analysed the distributions of the vegetation classes and managed burning using detrended correspondence analysis. Results Classification accuracy was c. 95% and produced a 5‐m resolution map for 514 km² of moorland. Cover classes were highly aggregated and strong nonlinear effects of elevation and slope and weaker effects of aspect and bedrock type were evident in structuring moorland vegetation communities. The classification revealed the spatial distribution of managed burning and suggested that relatively steep areas may be disproportionately burnt. Main conclusions Random Forest classification of aerial imagery is an efficient method for producing high‐resolution maps of upland vegetation. These may be used to monitor long‐term changes in vegetation and management burning and infer species–environment relationships and can therefore provide an important tool for effective conservation at the landscape scale.     

Seasonal changes in prevalence and intensity of Hypoderma actaeon in Cervus elaphus from central Spain

Hypodermosis in red deer, Cervus elaphus Linnaeus (Artilodactyla: Cervidae), caused by the warble fly, Hypoderma actaeon Latreille (Diptera: Oestridae), was studied at Quintos de Mora (Toledo, Spain) over a one-year period between October 1994 and September 1995. One hundred and twenty-five red deer were examined for the presence of warble fly larvae. The prevalence of warbles was 44.8% and the intensity of infection was 38.29 (SD +/- 61.32) warbles/deer infected. Clear seasonal variations were observed in prevalence and intensity, with the highest values in the autumn and winter. Statistically significant differences were observed in prevalence and intensity among age groups. In contrast, no differences were found in prevalence and intensity between males and females.     

马鹿阿拉善亚种遗传多样性和群体结构

马鹿阿拉善亚种（Cervus elaphus alashanicus）又称阿拉善马鹿,目前仅分布于贺兰山地区,是我国马鹿亚种分布范围最狭窄的一个隔离种群。为了解阿拉善马鹿的种群遗传多样性及遗传变异情况,以对该种群的保护提供科学参考,对在贺兰山采集的93个野生个体新鲜粪便样本的线粒体控制区部分序列（991 bp）进行扩增和分析,共检测到68个变异位点,定义16种单倍型,平均单倍型多样性为0.405,平均核苷酸多样性为0.00232,说明种群遗传多样性水平较低。中性检验和错配分布分析表明阿拉善马鹿曾出现过种群扩张,贝叶斯天际线分析（BSP）显示扩张时间约在末次冰盛期（0.028—0.010 Ma）。FST检验表明阿拉善马鹿种群内存在显著遗传分化,系统发育树和单倍型网络图分析表明群体间没有明显的系统地理格局。本研究表明阿拉善马鹿目前种群遗传多样性较低,建议加大对该亚种的关注和保护力度。       

Sex-Specific Elk Resource Selection during the Anthrax Risk Period

Anthrax, caused by the spore-forming bacterium Bacillus anthracis, is a zoonosis affecting animals and humans globally. In the United States, anthrax outbreaks occur in wildlife and livestock, with frequent outbreaks in native and exotic wildlife species in Texas, livestock outbreaks in the Dakotas, and sporadic mixed outbreaks in Montana. Understanding where pathogen and host habitat selection overlap is essential for anthrax management. Resource selection and habitat use of ungulates may be sex-specific and lead to differential anthrax exposure risks across the landscape for males and females. We evaluated female elk (Cervus canadensis) resource selection in the same study areas as male elk in a previous anthrax risk study to identify risk of anthrax transmission to females and compare transmission risk between females and males. We developed a generalized linear mixed-effect model to estimate resource selection for female elk in southwest Montana during the June to August anthrax transmission risk period. We then predicted habitat selection of female and male elk across the study area and compared selection with the distribution of anthrax risk to identify spatial distributions of potential anthrax exposure for the male and female elk. Female and male elk selected different resources during the anthrax risk period, which resulted in different anthrax exposure areas for females and males. The sex-specific resource selection and habitat use could infer different areas of risk for anthrax transmission, which can improve anthrax and wildlife management and have important public health and economic implications. © 2020 The Wildlife Society.     

Temporal Overlap Among Feral Horses,Cattle, and Native Ungulates at Water Sources

Feral horse (Equus ferus caballus) populations on public rangelands in the western United States threaten forage production for livestock and wildlife habitat. Interference competition between feral horses and heterospecifics at watering sources can have negative effects on livestock and wildlife. Researchers have documented altered timing and behavior of wild ungulates at water sources when horses were present. The few studies examining these interactions have infrequently occurred within areas specifically managed for feral equids and have not occurred in sites with cattle. We used motion-sensitive cameras at 8 watering sources to document watering activity patterns and construct indices of temporal overlap among feral horses, cattle, elk (Cervus canadensis), mule deer (Odocoileus hemionus), and pronghorn (Antilocapra americana) within the Adobe Town Herd Management Area in southern Wyoming, USA, between June and September 2018 and 2019. Feral horses, cattle, and pronghorn exhibited a high degree of temporal overlap (>79%) in water use, with feral horses and pronghorn exhibiting the highest estimated percent overlap (88.1%, 95% CI = 86.5–89.6%). Mule deer and elk watering activity also overlapped with horses and cattle but to a lesser degree (<55%). Feral horses spent a mean of 16.7 ± 30.5 (SD) minutes during a watering event and were present at a given water source on average 4.5 ± 6.3% and up to 34.9% of the day, which is less than reported in previous studies. Cattle spent on average 23.5 ± 44.9 minutes during a watering event, and were present on average 4.2 ± 7.7% and up to 42.4% of the day at a single water source. Results of generalized linear mixed-effects models indicated that number of conspecifics was the strongest predictor of visit duration for pronghorn and horses; hour of the day and group size of heterospecifics were informative, but less important, variables. There was no difference in peak visitation time for any species between sites of high versus low horse or cattle use. Despite temporal overlap, we did not find evidence of interference competition between feral horses, cattle, and pronghorn. We recommend future examination of interference competition and its biological consequences between introduced and native ungulates at water sources of varying size across sites, equid population levels, and livestock stocking rates. © 2020 The Wildlife Society.     

Abiotic,bottom-up,and top-down influences on recruitment of Rocky Mountain elk in Oregon: A retrospective analysis

Understanding the relative effects of the many factors that may influence recruitment of ungulates is fundamental to managing their populations. Over the last 4 decades, average recruitment in some populations of elk (Cervus elaphus) in Oregon, USA declined from >50 to <20 juveniles per 100 females, and several competing hypotheses address these declines. We developed a priori models and constructed covariates spanning 1977–2005 from hunter-killed elk, elk population estimates, cougar harvest, and weather statistics to evaluate abiotic, bottom-up, and top-down factors that may explain annual variation and long-term trends of pregnancy, juveniles-at-heel in late autumn, and recruitment of juvenile elk in spring. In models of pregnancy status, August precipitation, age, and cougar index had positive effects, whereas previous year (t − 1) winter severity or winter precipitation_(t−1) and elk density had negative effects. In models of juvenile-at-heel in late autumn, August precipitation, August precipitation_(t−1), cougar index × elk density_(t−1), and age had positive effects, whereas cougar index, elk density_(t−1), and winter precipitation_(t−1) had negative effects. Juvenile recruitment was best explained by positive effects of August precipitation_(t−1), lactation rate, and cougar index × elk density_(t−1) and negative effects of cougar index and elk density_(t−1). Winter severity, precipitation, and temperature were not significant in explaining variation in elk recruitment. Annual variation in pregnancy, juvenile-at-heel, and recruitment was most influenced by August precipitation, whereas long-term trends in recruitment were most influenced by cougar densities with relatively weak effects of elk density. These results provide insight into causes of year-to-year and long-term trends of elk recruitment and provide a basis for more rigorous evaluation of factors affecting recruitment of elk. © 2012 The Wildlife Society.     

Parents’ genetic dissimilarity and offspring sex in a polygynous mammal

Offspring quality may benefit from genetic dissimilarity between parents. However, genetic dissimilarity may trade‐off with additive genetic benefits. We hypothesized that when sexual selection produces sex‐specific selective scenarios, the relative benefits of additive genetic vs. dissimilarity may differ for sons and daughters. Here we study a sample of 666 red deer (Cervus elaphus) microsatellite genotypes, including males, females and their foetuses, from 20 wild populations in Spain (the main analyses are based on 241 different foetuses and 190 mother‐foetus pairs). We found that parental lineages were more dissimilar in daughters than in sons. On average, every mother was less related to her mate than to the sample of fathers in the population when producing daughters not sons. Male foetuses conceived early in the rutting season were much more inbred than any other foetuses. These differences maintained through gestation length, ruling out intrauterine mortality as a cause for the results, and indicating that the potential mechanism producing the association between parents’ dissimilarity and offspring sex should operate close to mating or conception time. Our findings highlight the relevance of considering the sex of offspring when studying genetic similarity between parents.     

Decomposing variation in population growth into contributions from environment and phenotypes in an age-structured population

Evaluating the relative importance of ecological drivers responsible for natural population fluctuations in size is challenging. Longitudinal studies where most individuals are monitored from birth to death and where environmental conditions are known provide a valuable resource to characterize complex ecological interactions. We used a recently developed approach to decompose the observed fluctuation in population growth of the red deer population on the Isle of Rum into contributions from climate, density and their interaction and to quantify their relative importance. We also quantified the contribution of individual covariates, including phenotypic and life-history traits, to population growth. Fluctuations in composition in age and sex classes ((st)age structure) of the population contributed substantially to the population dynamics. Density, climate, birth weight and reproductive status contributed less and approximately equally to the population growth. Our results support the contention that fluctuations in the population's (st)age structure have important consequences for population dynamics and underline the importance of including information on population composition to understand the effect of human-driven changes on population performance of long-lived species.