Global declines of caribou and reindeer

Caribou and reindeer herds are declining across their circumpolar range, coincident with increasing arctic temperatures and precipitation, and anthropogenic landscape change. Here, we examine the mechanisms by which climate warming and anthropogenic landscape change influence caribou and reindeer population dynamics, namely changes in phenology, spatiotemporal changes in species overlap, and increased frequency of extreme weather events, and demonstrate that many caribou and reindeer herds show demographic signals consistent with these changes. While many caribou and reindeer populations historically fluctuated, the current, synchronous population declines emphasize the species' vulnerability to global change. Loss of caribou and reindeer will have significant, negative socioeconomic consequences for northern indigenous cultures.     

Impacts of climate change on the seasonal distribution of migratory caribou

Arctic ecosystems are especially vulnerable to global climate change as temperature and precipitation regimes are altered. An ecologically and socially highly important northern terrestrial species that may be impacted by climate change is the caribou, Rangifer tarandus . We predicted the current and potential future occurrence of two migratory herds of caribou [Rivière George herd (RG) and Rivière-aux-Feuilles (RAF) herd] under a Canadian General Circulation Model climate change scenario, across all seasons in the Québec–Labrador peninsula, using climatic and habitat predictor variables. Argos satellite-tracking collars have been deployed on 213 caribou between 1988 and 2003 with locations recorded every 4–5 days. In addition, we assembled a database of climate (temperature, precipitation, snowfall, timing and length of growing season) and habitat data obtained from the SPOT VEGETATION satellite sensor. Logistic regression models indicated that both climatic and physical habitat variables were significant predictors of current migratory caribou occurrence. Migratory caribou appeared to prefer regions with higher snowfall and lichen availability in the fall and winter. In the summer, caribou preferred cooler areas likely corresponding to a lower prevalence of insects, and they avoided disturbed and recently burnt areas. Climate change projections using climate data predicted an increased range for the RAF herd and decreased range for the RG herd during 2040–2069, limiting the herds to northeastern regions of the Québec–Labrador peninsula. Direct and indirect consequences of climate change on these migratory caribou herds possibly include alteration in habitat use, migration patterns, foraging behaviour, and demography, in addition to social and economic stress to arctic and subarctic native human populations.     

Coyote Habitat Selection and Management Implications for the Gaspésie Caribou

ABSTRACT Anthropogenic disturbances can promote establishment and growth of predator populations in areas where secondary prey can then become threatened. In this study, we investigated habitat selection of eastern coyotes (Canis latrans), a relatively new predator in the vicinity of an endangered population of caribou (Rangifer tarandus caribou). We hypothesized that coyotes in the boreal forest depend mainly on disturbed habitat, particularly that of anthropogenic origin, because these habitats provide increased food accessibility. Coyotes would likely take advantage of moose (Alces alces) carcasses, berries, and snowshoe hares (Lepus americanus) found in open habitats created by logging. To test these predictions, we described coyote diet and habitat selection at different spatial and temporal levels and then compared resource availability between habitats. To do so, we installed Global Positioning System radiocollars on 23 individual coyotes in the Gaspésie Peninsula, eastern Québec, Canada. Coyotes selected clear-cuts of 5–20 years and avoided mature coniferous forests both at the landscape and home-range levels. Clear-cuts of 5–20 years were found to contain a high availability of moose carcasses and berries, and vulnerability of snowshoe hares is known to increase in clear-cuts. The importance of these 3 food resources was confirmed by the characteristics of core areas used by coyotes and diet analysis. Moose remains were found at 45% of core areas and coyote diet comprised 51% moose on an annual basis. Anthropogenic disturbances in the boreal forest thus seem to benefit coyotes. Our results indicated that the relationship between coyotes and caribou likely involves spillover predation. This knowledge allows managers to consider spillover predation by coyotes as a possible threat for endangered caribou population when the predator depends mainly on habitat of anthropogenic origin and to suggest methods to alleviate it when developing management plans.     

基于生境可获得性的完达山地区马鹿(Cervus elaphus xanthopygus)冬季生境选择

于2004～2005年冬季研究了完达山地区马鹿的生境利用和选择。在野外调查的基础上,获取了研究地区马鹿种群水平上的生境利用数据;利用地理信息系统和遥感技术,从区域尺度上测度了各类生境因子的可获得性。通过比较被利用生境与可获得生境,测度了马鹿冬季对各类生境或生态因子的选择。结果表明,马鹿对植被类型、海拔、坡向、NDVI等级、到公路距离表现出非比例利用,对坡度的利用与其可获得性则没有显著性差异。马鹿选择采伐迹地,低郁闭度生境（第2、3NDVI等级）,200～300m海拔区间,南坡,距离公路600～700m的区间。马鹿采食生境和卧息生境对各类因子具有不同的选择性,表现出不同功能生境分离的特征。对于采食生境,马鹿选择采伐迹地、阔叶疏林,低郁闭度（第2、3NDVI等级）,南坡;对于卧息生境,马鹿仅选择采伐迹地,低郁闭度（第2、3、4NDVI等级）。根据马鹿活动样点的出现与否,建立了马鹿冬季生境选择的逻辑斯谛回归模型。模型回判结果表明,该模型对马鹿活动样方与对照样方的总体正确预测率为74．4％,对马鹿活动样方的正确预测率为84．2％,对对照样方的正确预测率为62．4％,能够较好的预测生境利用概率。     

A data-driven demographic model to explore the decline of the Bathurst caribou herd

The Bathurst herd of barren-ground caribou (Rangifer tarandus groenlandicus) in the Canadian central arctic declined from an estimated 203,800 to 16,400 breeding females from 1986 to 2009, with the most rapid decline from 2006 to 2009. A key research and management question was whether the decline was mainly due to decreases in productivity alone or also due to reduced adult female survival. Investigating causes of the decline was hampered by a lack of direct estimates of caribou demographic parameters. We developed a demographic model that could be objectively fitted to field data to explore the mechanisms for the Bathurst decline, with a focus on the recent accelerated decline from 2006 to 2009. Our modeling indicated that the decline was driven by increasing negative trends in adult female and calf survival rates and possibly reduced fecundity The effect of a constant hunter harvest on the declining herd was one potential cause for the recent accelerated decline in adult survival. The demographic model detected negative trends in adult female survival that were not detected using standalone analyses of collar-based survival data. The model allowed rigorous interpretation of trends in productivity by controlling for the simultaneous influence of trends in adult, calf, and yearling survival and adult fecundity on field-based calf–cow ratios. Stochastic simulations suggested that large increases in adult survival and productivity would be needed for the herd to recover. Our methods enable objective modeling of caribou demography that can assist in caribou management based upon all sources of available data. © 2011 The Wildlife Society.     

Habitat selection in a fluctuating ground squirrel population: Density‐dependence and fitness consequences

Investigating individual‐based habitat settlement decisions is a central theme in ecology, yet studies that quantify density‐dependent habitat selection or tie fitness to resource selection decisions remain rare. We quantified habitat selection in golden‐mantled ground squirrels (Callospermophilus lateralis) across two spatial scales (home‐range placement, and occurrence within the home range) by using 11 consecutive years of data on individual space use, and we used resource selection functions and multilevel modeling to address how habitat preferences may be influenced by density or linked to fitness outcomes. Squirrels preferred dry meadow over other habitat types (wet meadow, aspen, spruce, and willow) at both spatial scales. Squirrels were more likely to use dry meadow that contained shorter vegetation and vision‐enhancing prominences such as rocks (“perches”). The use of dry meadow at each scale was not influenced by changes in density. The use of dry meadow did not lead to increased litter size, pre‐hibernation mass, or survival. However, squirrels that experienced a greater number of perches or lower local densities had higher survival rates. Our results suggest that a lack of visual obstruction, probably facilitating detection of predators, drives habitat selection in this system. Surprisingly, squirrels maintained their preference for dry meadow as density increased, and they experienced reduced survival as a result. This work furthers our understanding about the causes and consequences of changes in habitat use, informing wildlife management and conservation.     

The impact of population bottlenecks on fluctuating asymmetry and morphological variance in two separate populations of reindeer on the island of South Georgia

In the early part of the 20^th century, whalers on South Georgia in the South Atlantic transported reindeer from Norway to establish a population from which they could cull animals for food. This happened twice, with reindeer obtained from the same source in each case, and with independent founder populations being established on separate parts of the island. As the exact number of founding males and females are known in each case, and as it was possible to obtain materials from the source population, this provided an unusually clear test of expectations about the impact of population bottlenecks on morphological and genetic diversity. In this study, we focus on the impact on morphological variation and on the relationship between genomic stress and indirect measures of fitness. We find that fluctuating asymmetry and morphological variation increased in each bottlenecked population and that the impact was somewhat stronger for the founder group that began with fewer females. Based on several skull measurements, there was also a significant trend for the reindeer in the bottlenecked populations to have smaller skulls. There were consistent correlations between individual genetic diversity and indirect measures of fitness, but these were weak and non‐significant after correction for type 1 error. Taken together, these data support the expectation that genomic stress has the potential to impact the expression of morphological phenotype in a large mammal and provide an opportunity to directly compare two parallel events. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 102 , 798–811.     

Woodland caribou calf mortality in Newfoundland: insights into the role of climate,predation and population density over three decades of study

The rates and causes of juvenile mortality are central features of the dynamics and conservation of large mammals, like woodland caribou (Rangifer tarandus caribou (Gmelin, 1788)), but intrinsic and extrinsic factors may be modified by variations in animal abundance. We tested the influences of population size, climate, calf weight and sex on survival to 6 months of age of 1241 radio-collared caribou calves over three decades, spanning periods of population growth (1979–1997) and decline (2003–2012) in Newfoundland, Canada. Daily survival rates were higher and rose more quickly with calf age during the population growth period compared to the decline. Population size (negatively) and calf weight (positively) affected survival during the decline but neither had a detectable influence during the growth phase. Sex, climate and plant productivity (the latter two derived from the North Atlantic Oscillation and Normalized Difference Vegetation Index, respectively) exerted minimal influence during either phase. Predation was the dominant source of mortality. The mean percentage of calves killed by predators was 30 % higher during the decline compared to the growth phase. Black bears (Ursus americanus) and lynx (Lynx canadensis) were the major predators during the population increase but this changed during the decrease to black bears and coyotes (Canis latrans). Our findings are consistent with the hypothesis that Newfoundland caribou experienced phase-dependent survival mediated proximally by predation and competition for food.     

Habitat selection by wapiti (Cervus elaphus xanthopygus) in Wandashan Mountains, China, based on habitat availability

In 2004 and 2005, we studied winter habitat use and selection by wapiti in Wandashan Mountains, Heilongjiang Province, China. Using Geographic Information System (GIS) and Remote Sensing (RS), we measured habitat availability in terms of the area of each habitat category in the study area. We compared winter habitats used by wapiti and their availability. The results showed that the habitats used by wapiti were disproportional to their availability. Wapiti preferred clear-cuttings, low vegetation coverage (No. 2, 3 NDVI classes), 200–300 m elevation range, south aspect, and 600–700 m distance range away from roads. They also showed different preferences for feeding and resting. The feeding sites tended to be located at broad-leaved stands and clear-cuttings, No. 2, 3 NDVI classes, and south slope, whereas the bedding sites tended to be clear-cuttings, and No. 2, 3, 4 NDVI classes. Using the logistic regression model to predict the probability of habitat use by wapiti in winter, we found that the overall prediction accuracy was 74.4% for the total habitat samples, with 84.2% for the habitat samples used by wapiti and 62.4% for the control samples correctly predicted by using this model.     

Habitat selection,interspecific interactions and landscape composition

Summary I argue here that, from the perspective of any individual, most landscapes are composed of only three basic types of habitats. These are: (1) source habitat in which reproduction exceeds mortality and the expected per capita growth rate is greater than one; (2) sink habitat, in which limited, reproduction is possible but will not on average, compensate for mortality and the per capita rate of growth is between zero and one; and (3) unusable habitat, which comprises the matrix of all habitats that are never exploited by the species in question, and in which patches of source and sink habitats are embedded. Unlike earlier source-sink models, this model explicitly considers the effects that substituting one type of habitat for another has on the equilibrium size of a population and the interactions between species which can use both source and sink habitats. The model demonstrates that the equilibrium size of a species' population can sometimes be increased by substituting unusable habitat for sink habitat. Thus, even though the average patch quality in the landscape may be decreased, the overall quality of the landscape can increase. For two species with distinct habitat preferences, interactions between species can vary qualitatively as well as quantitatively as a function of the relative abundances of each of the habitat types. The model also shows that the interactions between species are particularly sensitive to the relative costs of moving between patches and sampling patches to determine their quality. Recent fragmentation of natural landscapes may increase the cost of searching for usable (source or sink) patches. Under some conditions, the interspecific interactions may be substantially more negative (competitive) than the interactions that evolved in the original natural landscape, further reducing population sizes and increasing the likelihood of competitive exclusion in fragmented modern landscapes.     

Population size and major valleys explain microsatellite variation better than taxonomic units for caribou in western Canada

Identifying conservation units below the species level is becoming increasingly important, particularly when limited resources necessitate prioritization for conservation among such units. This problem is exemplified with caribou, a mammal with a circum-Arctic distribution that is exposed to a broad spectrum of ecological conditions, but is also declining in many parts of its range. We used microsatellite markers to evaluate the suitability of existing intra-specific taxonomic designations to act as population units for conservation and contrasted this with landscape features that were independent of taxonomy. We also quantified the relationship between genetic differentiation and subpopulation size, a factor that has been under-represented in landscape genetic research. Our data set included three subspecies and three ecotypes of caribou that varied in population size by five orders of magnitude. Our results indicated that genetic structure did not correspond to existing taxonomic designation, particularly at the level of ecotype. Instead, we found that major valleys and population size were the strongest factors associated with substructure. There was a negative exponential relationship between population size and F(ST) between pairs of adjacent subpopulations, suggesting that genetic drift was the mechanism causing the structure among the smallest subpopulations. A genetic assignment test revealed that movement among subpopulations was a fraction of the level needed to stabilize smaller subpopulations, indicating little chance for demographic rescue. Such results may be broadly applicable to landscape genetic studies, because population size and corresponding rates of drift have the potential to confound interpretations of landscape effects on population structure.     

小相岭大熊猫与放牧家畜的生境选择

利用 Forage Ratio指数对小相岭山系大熊猫与放牧牲畜的生境选择进行了比较研究 ,研究涉及 1 1种生境因子。研究结果表明 ,大熊猫喜欢选择在山体的脊部和中部的凸坡 ,坡向南坡 ,喜欢选择 0～ 2 4 %的灌木盖度 ,喜欢竹子盖度大于 5 0 %的原始针叶林 ,对坡度、乔木高度、乔木郁闭度、灌木高度不存在选择性 ,都为随机利用。放牧牲畜喜欢选择利用复合坡、山体的下部、坡度小于 2 0°的山坡 ;喜欢利用的生境类型是草坡和灌丛 ;选择的森林起源是次生林 ;所利用生境的乔木高度为 5～ 9m,对坡向、乔木郁闭度、灌木高度、灌木盖度、竹子盖度都随机利用。放牧家畜与大熊猫在对生境因子的利用上有许多共同点 ,对许多因子类型大多都是随机利用 ,因而 ,在对一些生境因子的利用上 ,放牧对大熊猫的活动会产生一定的影响。同时 ,它们在生境选择上也存在一定的差异 ,特别是在对植被类型和森林起源的选择上差异较大 ,只要合理的规划和控制放牧活动 ,也就可能达到大熊猫保护与社区经济协调发展的目的     

The role of predation in the decline and extirpation of woodland caribou

To select appropriate recovery strategies for endangered populations, we must understand the dynamics of small populations and distinguish between the possible causes that drive such populations to low numbers. It has been suggested that the pattern of population decline may be inversely density-dependent with population growth rates decreasing as populations become very small; however, empirical evidence of such accelerated declines at low densities is rare. Here we analyzed the pattern of decline of a threatened population of woodland caribou (Rangifer tarandus caribou) in British Columbia, Canada. Using information on the instantaneous rate of increase relative to caribou density in suitable winter foraging habitat, as well as on pregnancy rates and on causes and temporal distribution of mortalities from a sample of 349 radiocollared animals from 15 subpopulations, we tested 3 hypothesized causes of decline: (a) food regulation caused by loss of suitable winter foraging habitat, (b) predation-sensitive foraging caused by loss of suitable winter foraging habitat and (c) predation with caribou being secondary prey. Population sizes of caribou subpopulations ranged from <5 to >500 individuals. Our results showed that the rates of increase of these subpopulations varied from −0.1871 to 0.0496 with smaller subpopulations declining faster than larger subpopulations. Rates of increase were positively related to the density of caribou in suitable winter foraging habitat. Pregnancy rates averaged 92.4% ±2.24 and did not differ among subpopulations. In addition, we found predation to be the primary cause of mortality in 11 of 13 subpopulations with known causes of mortality and predation predominantly occurred during summer. These results are consistent with predictions that caribou subpopulations are declining as a consequence of increased predation. Recovery of these woodland caribou will thus require a multispecies perspective and an appreciation for the influence of inverse density dependence on population trajectories.     

潭清苏铁的生境、种群结构与动态的研究

对小黑江流域潭清苏铁的生境、种群结构与动态进行了研究。结果表明．小黑江流域的自然地带性植被主要为热带雨林,海拔600m以下的原生植被为典型热带北缘季雨林,而海拔600～1000m的原生植被为山地雨林。其原生植被遭到破坏后,土壤流失严重．生态环境向干旱、贫瘠化发展,从而导致其次生植被都向山地雨林演化,加上人类活动的继续存在,不可能在短期内恢复成原生植被类型——热带季雨林或山地雨林。醛管其生态环境发生了显著的变化,但潭清苏铁的生存、繁衍正常。这也表明潭清苏铁对其环境变化有一定的适应能力。潭清苏铁种群的年龄结构基本呈金字塔形,属较稳定的结构。但是．种群的成年个体数明显偏小,成了潭清苏铁种群生存繁衍的“瓶颈”．也反映出了潭清苏铁曾经遭受过严重破坏的事实．虽然潭清苏铁对生态环境的变化有一定的适应能力．似抗人为破坏的能力较弱。潭清苏铁生长发育很缓慢．种群恢复的周期较长,大约是30～40a。目前．潭清苏铁种群正处于恢复、上升阶段。就地保护可能是其最有效的保护途径之一。目前,潭清苏铁被列为国家一级保护植物,其分布区——小黑江流域已成为黄连山国家级自然保护区的一部分。如果其现有的生态环境得到有效保护,且在没有人为破坏的前提下．潭清苏铁不会沦为濒危物种。