Influence of Campsites on Black Bear Habitat Use and Potential Impact on Caribou Restoration

Ursus americanus(black bear) predation could limit the success of the proposed restoration of Rangifer tarandus (woodland caribou) to Minnesota. The problem was recently identified as a major factor in the failure of a similar restoration effort in Maine. During the summer of 1991 we conducted a survey in the region of the proposed restoration, using bait stations to identify bear presence. Four settings were sampled: islands with campsites, islands without campsites, mainland areas with campsites, and mainland areas without campsites. Results from the survey suggest that black bears use areas with campsites more than those without. Whereas caribou may use islands preferentially for calving to escape predation, islands with campsites may be unfavorable for caribou calf survival due to frequent bear visitation.     

The Caribou Migration Model for Arctic Hadrosaurs (Dinosauria: Ornithischia): A Reassessment

The recovery of abundant dinosaur fossils from high paleolatitudes of northern Alaska has raised some hard questions in relation to any available model of dinosaur physiology. To explain the occurrence of hadrosaurs at high ancient latitudes, a model involving long-distance migration analogous to that of the modern caribou has been proposed. The model calls for seasonal movements over great latitudinal distances by these Cretaceous hadrosaurs. This model is reassessed in terms of the growth, body sizes, and inferred physiological ecology of the hadrosaurs and the caribou. Histological data suggest that juvenile hadrosaurs obtained from northern Alaska were greater than 1 year in age. Comparison of the relative sizes of juvenile and adult hadrosaurs with juvenile and adult caribou suggests, based on qualitative energetics, that the juvenile hadrosaurs were too small to participate in long-distance migration. The "hadrosaurs as caribou" model provides clues to the feeding ecology of North Slope hadrosaurs, if they are reinterpreted as year-round residents of high latitudes. However, it does not constitute a satisfactory basis on which to infer long-distance seasonal migrations by these animals.     

Metagenomic Survey for Viruses in Western Arctic Caribou,Alaska, through Iterative Assembly of Taxonomic Units

Pathogen surveillance in animals does not provide a sufficient level of vigilance because it is generally confined to surveillance of pathogens with known economic impact in domestic animals and practically nonexistent in wildlife species. As most (re-)emerging viral infections originate from animal sources, it is important to obtain insight into viral pathogens present in the wildlife reservoir from a public health perspective. When monitoring living, free-ranging wildlife for viruses, sample collection can be challenging and availability of nucleic acids isolated from samples is often limited. The development of viral metagenomics platforms allows a more comprehensive inventory of viruses present in wildlife. We report a metagenomic viral survey of the Western Arctic herd of barren ground caribou (Rangifer tarandus granti) in Alaska, USA. The presence of mammalian viruses in eye and nose swabs of 39 free-ranging caribou was investigated by random amplification combined with a metagenomic analysis approach that applied exhaustive iterative assembly of sequencing results to define taxonomic units of each metagenome. Through homology search methods we identified the presence of several mammalian viruses, including different papillomaviruses, a novel parvovirus, polyomavirus, and a virus that potentially represents a member of a novel genus in the family Coronaviridae.     

Modeling Caribou Movements: Seasonal Ranges and Migration Routes of the Central Arctic Herd

Migration is an important component of the life history of many animals, but persistence of large-scale terrestrial migrations is being challenged by environmental changes that fragment habitats and create obstacles to animal movements. In northern Alaska, the Central Arctic herd (CAH) of barren-ground caribou (Rangifer tarandus granti) is known to migrate over large distances, but the herd’s seasonal distributions and migratory movements are not well documented. From 2003–2007, we used GPS radio-collars to determine seasonal ranges and migration routes of 54 female caribou from the CAH. We calculated Brownian bridges to model fall and spring migrations for each year and used the mean of these over all 4 years to identify areas that were used repeatedly. Annual estimates of sizes of seasonal ranges determined by 90% fixed kernel utilization distributions were similar between summer and winter ($\bar{X}$ = 27,929 SE = 1,064 and $\bar{X}$ = 26,585 SE = 4912 km², respectively). Overlap between consecutive summer and winter ranges varied from 3.3–18.3%. Percent overlap between summer ranges used during consecutive years ($\bar{X}$ = 62.4% SE = 3.7%) was higher than for winter ranges ($\bar{X}$ = 42.8% SE = 5.9%). Caribou used multiple migration routes each year, but some areas were used by caribou during all years, suggesting that these areas should be managed to allow for continued utilization by caribou. Restoring migration routes after they have been disturbed or fragmented is challenging. However, prior knowledge of movements and threats may facilitate maintenance of migratory paths and seasonal ranges necessary for long-term persistence of migratory species.     

Interactive Effects Between Reindeer and Habitat Fertility Drive Soil Nutrient Availabilities in Arctic Tundra

Herbivores impact nutrient availability and cycling, and the net effect of herbivory on soil nutrients is generally assumed to be positive in nutrient-rich environments and negative in nutrient-poor ones. This is, however, far from a uniform pattern, and there is a recognized need to investigate any interactive effects of herbivory and habitat fertility (i.e., plant C/N ratios) on soil nutrient availabilities. We determined long-term effects of reindeer on soil extractable nitrogen (N) and phosphorus (P) and their net mineralization rates along a fertility gradient of plant carbon (C) to N and P ratios in arctic tundra. Our results showed that reindeer had a positive effect on soil N in the more nutrient-poor sites and a negative effect on soil P in the more nutrient-rich sites, which contrasts from the general consensus. The increase in N availability was linked to a decrease in plant and litter C/N ratios, suggesting that a shift in vegetation composition toward more graminoids favors higher N cycling. Soil P availability was not as closely linked to the vegetation and is likely regulated more by herbivore-induced changes in soil physical and chemical properties. The changes in soil extractable N and P resulted in higher soil N/P ratios, suggesting that reindeer could drive the vegetation toward P-limitation. This research highlights the importance of including both the elements N and P and conducting studies along environmental gradients in order to better understand the interactive effects of herbivory and habitat fertility on nutrient cycling and primary production.     

Projected Polar Bear Sea Ice Habitat in the Canadian Arctic Archipelago

Background

Sea ice across the Arctic is declining and altering physical characteristics of marine ecosystems. Polar bears (Ursus maritimus) have been identified as vulnerable to changes in sea ice conditions. We use sea ice projections for the Canadian Arctic Archipelago from 2006 – 2100 to gain insight into the conservation challenges for polar bears with respect to habitat loss using metrics developed from polar bear energetics modeling.

Principal Findings

Shifts away from multiyear ice to annual ice cover throughout the region, as well as lengthening ice-free periods, may become critical for polar bears before the end of the 21^st century with projected warming. Each polar bear population in the Archipelago may undergo 2–5 months of ice-free conditions, where no such conditions exist presently. We identify spatially and temporally explicit ice-free periods that extend beyond what polar bears require for nutritional and reproductive demands.

Conclusions/Significance

Under business-as-usual climate projections, polar bears may face starvation and reproductive failure across the entire Archipelago by the year 2100.     

Photoheterotrophic Microbes in the Arctic Ocean in Summer and Winter

Photoheterotrophic microbes, which are capable of utilizing dissolved organic materials and harvesting light energy, include coccoid cyanobacteria (Synechococcus and Prochlorococcus), aerobic anoxygenic phototrophic (AAP) bacteria, and proteorhodopsin (PR)-containing bacteria. Our knowledge of photoheterotrophic microbes is largely incomplete, especially for high-latitude waters such as the Arctic Ocean, where photoheterotrophs may have special ecological relationships and distinct biogeochemical impacts due to extremes in day length and seasonal ice cover. These microbes were examined by epifluorescence microscopy, flow cytometry, and quantitative PCR (QPCR) assays for PR and a gene diagnostic of AAP bacteria (pufM). The abundance of AAP bacteria and PR-containing bacteria decreased from summer to winter, in parallel with a threefold decrease in the total prokaryotic community. In contrast, the abundance of Synechococcus organisms did not decrease in winter, suggesting that their growth was supported by organic substrates. Results from QPCR assays revealed no substantial shifts in the community structure of AAP bacteria and PR-containing bacteria. However, Arctic PR genes were different from those found at lower latitudes, and surprisingly, they were not similar to those in Antarctic coastal waters. Photoheterotrophic microbes appear to compete successfully with strict heterotrophs during winter darkness below the ice, but AAP bacteria and PR-containing bacteria do not behave as superior competitors during the summer.Photoheterotrophy, which is the ability to utilize organic substrates and to harvest light energy, occurs in a broad range of microbes (14). Phototrophic microbes should be included in models of carbon cycling and food web dynamics, which now typically include only photoautotrophs, which produce organic carbon and oxygen, and heterotrophs, which consume organic matter and oxygen via aerobic respiration (55). Photoheterotrophy is potentially an important competitive adaptation, enabling microbes to survive adverse conditions or to outgrow competitors. Photoheterotrophic microbes include proteorhodopsin (PR)-containing bacteria, aerobic anoxygenic phototrophic (AAP) bacteria, and cyanobacteria.PR is a membrane protein that binds retinal and functions as a light-driven proton pump that can have several physiological functions, including ATP generation (15). The actual role of PR in the environment is uncertain, however. Light enhances the growth of some PR-containing bacteria, such as Dokdonia sp. (17), but has no effect on the growth of others, including Pelagibacter ubique (16) and the SAR92-like strain HTCC2207 (44). Similarly, Campbell et al. (4) found no significant correlation with light intensity for three of four PR gene types examined in the North Atlantic Ocean. Nevertheless, emerging biogeographic patterns of PR genes are providing clues about what controls the distribution and abundance of PR-containing photoheterotrophs in oceanic systems. One of the first oceanic environments to be examined for PR was the coastal waters near Palmer Station, Antarctica (2). Sequence analysis revealed that the Antarctic PRs differed from those isolated from Monterey Bay and surface waters in the central North Pacific (2). In spite of this early report, there has been no work on PR-containing bacteria in Arctic waters. PR-containing bacteria may have unique responses to the continuous summer light, winter darkness, and shading by seasonal ice cover that occur in high-latitude environments.The diversity and abundance of AAP bacteria have been examined by sequencing of the pufM gene (20, 51, 58), which is involved in bacteriochlorophyll (BChl a) synthesis, and by counting of BChl a-fluorescing cells by infrared fluorescence microscopy (14). Enumeration by infrared epifluorescence microscopy indicates that the abundance of AAP bacteria in environments such as the North Pacific Gyre and the Northeast Atlantic Ocean ranges from 1% to 10% (12, 13, 42) and can exceed 10% of the total prokaryotic community in estuaries (41, 50). AAP bacteria have been found in freshwater high-latitude waters (20, 35), but sequence analysis of pufM genes indicates that these AAP bacteria are distinct from those found in marine systems (50). The abundance of AAP bacteria decreases with latitude within the North Atlantic Ocean, from the central gyre to the waters near Greenland (13). Although these photoheterotrophic microbes are still present at 65°N, extrapolation of the trend suggests that AAP bacteria might be absent from the high-latitude waters of the Arctic Ocean.Polar waters appear to be an exception to the otherwise widespread distribution of coccoid cyanobacteria in the world oceans (33, 54). The abundance of Synechococcus and Prochlorococcus decreases with latitude, as exemplified by the 4-orders-of-magnitude decline in abundance between 44°S and 62°S in the South Atlantic Ocean (25). The abundance of Synechococcus also decreases with latitude in the North Atlantic Ocean, between the central gyre and the waters near Greenland, to a low level at 65°N (13). The strong correlation between abundance and temperature (25) suggests that coccoid cyanobacteria are not important at high latitudes, although there are scattered reports of Prochlorococcus in waters as far north as 60°N, near Iceland (27), and of Synechococcus in Antarctic coastal waters (53). However, more data are needed on the abundance of Synechococcus and Prochlorococcus in polar waters such as the Arctic Ocean.The goal of this study was to explore the abundance and diversity of photoheterotrophic microbes in the Arctic Ocean in order to develop a better picture of the biogeographic range of these biogeochemically important microbes and to gain insights into their ecology. Coastal waters of the Chukchi Sea and the Beaufort Sea were sampled in summer at the end of 24-h daylight and in winter following the period of 24-h darkness. The abundances of cyanobacteria, PR-containing bacteria, and AAP bacteria were monitored using flow cytometry, infrared epifluorescence microscopy, and real-time quantitative PCR (QPCR). These data provide a unique perspective on the potential impact of photoheterotrophic microbes on food webs and carbon cycling in this high-latitude aquatic system.     

Habitat selection,reproduction and predation of wintering lemmings in the Arctic

Snow cover has dramatic effects on the structure and functioning of Arctic ecosystems in winter. In the tundra, the subnivean space is the primary habitat of wintering small mammals and may be critical for their survival and reproduction. We have investigated the effects of snow cover and habitat features on the distributions of collared lemming (Dicrostonyx groenlandicus) and brown lemming (Lemmus trimucronatus) winter nests, as well as on their probabilities of reproduction and predation by stoats (Mustela erminea) and arctic foxes (Vulpes lagopus). We sampled 193 lemming winter nests and measured habitat features at all of these nests and at random sites at two spatial scales. We also monitored overwinter ground temperature at a subsample of nest and random sites. Our results demonstrate that nests were primarily located in areas with high micro-topography heterogeneity, steep slopes, deep snow cover providing thermal protection (reduced daily temperature fluctuations) and a high abundance of mosses. The probability of reproduction increased in collared lemming nests at low elevation and in brown lemming nests with high availability of some graminoid species. The probability of predation by stoats was density dependent and was higher in nests used by collared lemmings. Snow cover did not affect the probability of predation of lemming nests by stoats, but deep snow cover limited predation attempts by arctic foxes. We conclude that snow cover plays a key role in the spatial structure of wintering lemming populations and potentially in their population dynamics in the Arctic.     

Winter Habitat Preferences for Florida Manatees and Vulnerability to Cold

To survive cold winter periods most, if not all, Florida manatees rely on warm-water refuges in the southern two-thirds of the Florida peninsula. Most refuges are either warm-water discharges from power plant and natural springs, or passive thermal basins that temporarily trap relatively warm water for a week or more. Strong fidelity to one or more refuges has created four relatively discrete Florida manatee subpopulations. Using statewide winter counts of manatees from 1999 to 2011, we provide the first attempt to quantify the proportion of animals using the three principal refuge types (power plants, springs, and passive thermal basins) statewide and for each subpopulation. Statewide across all years, 48.5% of all manatees were counted at power plant outfalls, 17.5% at natural springs, and 34.9 % at passive thermal basins or sites with no known warm-water features. Atlantic Coast and Southwest Florida subpopulations comprised 82.2% of all manatees counted (45.6% and 36.6%, respectively) with each subpopulation relying principally on power plants (66.6% and 47.4%, respectively). The upper St. Johns River and Northwest Florida subpopulations comprised 17.8% of all manatees counted with almost all animals relying entirely on springs (99.2% and 88.6% of those subpopulations, respectively). A record high count of 5,076 manatees in January 2010 revealed minimum sizes for the four subpopulations of: 230 manatees in the upper St. Johns River; 2,548 on the Atlantic Coast; 645 in Northwest Florida; and 1,774 in Southwest Florida. Based on a comparison of carcass recovery locations for 713 manatees killed by cold stress between 1999 and 2011 and the distribution of known refuges, it appears that springs offer manatees the best protection against cold stress. Long-term survival of Florida manatees will require improved efforts to enhance and protect manatee access to and use of warm-water springs as power plant outfalls are shut down.     

Habitat selection and the scale of ghostly coexistence among Arctic rodents

Competition between coexisting species existing near their stable equilibrium can be obscured if they occupy separate habitats. Theories of habitat selection promise an ability to reveal the underlying ghost of competition by using isodars to infer the behavioural map of habitat selection. We tested the theory with two years of data on abundance and habitat preference by three Arctic rodent species living at low density along a gradient of wet to dry tundra on Herschel Island in Canada's western Arctic. Generalist brown lemmings exhibited a constant partial preference toward wet tundra whereas specialist collared lemmings and voles occupied the driest and wettest zones respectively. Although both lemming species compete for habitats elsewhere in the Canadian Arctic, isodar analyses suggest that the three species occupy wet and dry habitats independently of one another on Herschel Island. Competition at this large scale may be hidden at low densities, however, if the wet‐dry dichotomy is too coarse. Analyses at a finer subdivision of habitat revealed that these species coexist by using different microhabitats. Collared lemmings shifted their niche towards even drier habitat as the abundance of brown lemmings increased. We were thus able to reveal the ghost of competition lurking at large scales through a more refined analysis at smaller scales of density‐dependent habitat use.     

The Role of Habitat in the Persistence of Fire Ant Populations

The association of the exotic fire ant, Solenopsis invicta with man-modified habitats has been amply demonstrated, but the fate of such populations if ecological succession proceeds has rarely been investigated. Resurvey of a fire ant population in a longleaf pine plantation after 25 years showed that the recovery of the site from habitat disturbance was associated with a large fire ant population decline. Most of the persisting colonies were associated with the disturbance caused by vehicle tracks. In a second study, mature monogyne fire ant colonies that had been planted in experimental plots in native groundcover of the north Florida longleaf pine forest had mostly vanished six years later. These observations and experiments show that S. invicta colonies rarely persist in the native habitat of these pine forests, probably because they are not replaced when they die. A single site harbored a modest population of polygyne fire ants whose persistence was probably facilitated by reproduction through colony fission.     

Winter Temperature Affects the Prevalence of Ticks in an Arctic Seabird

The Arctic is rapidly warming and host-parasite relationships may be modified by such environmental changes. Here, I showed that the average winter temperature in Svalbard, Arctic Norway, explained almost 90% of the average prevalence of ticks in an Arctic seabird, the Brünnich’s guillemot Uria lomvia. An increase of 1°C in the average winter temperature at the nesting colony site was associated with a 5% increase in the number of birds infected by these ectoparasites in the subsequent breeding season. Guillemots were generally infested by only a few ticks (≤5) and I found no direct effect of tick presence on their body condition and breeding success. However, the strong effect of average winter temperature described here clearly indicates that tick-seabird relationships in the Arctic may be strongly affected by ongoing climate warming.     

湖北石首麇鹿的冬季生境选择

2005年11月至2006年2月,研究了石首麇鹿冬季的生境选择。共随机抽取了195个样方,其中石首麇鹿国家级自然保护区内111个,保护区外江南三合垸84个。在样方中测定了食物丰富度、距水源的距离、距林缘距离、距道路的距离、植被类型、距最近居民点的距离6种生境因子。用SPSS软件分别进行卡方检验、主成分分析和相关分析。结果表明：麇鹿选择食物丰富、距水源近且远离人为干扰的开阔生境;影响麇鹿冬季生境选择的3个主成分依次为食物因子、人为干扰因子、水源因子;鹿群大小与各生境因子相关不显著。该结果可为保护和改善石首麇鹿的栖息地提供参考。     

湖北石首麋鹿的冬季生境选择

2005年11月至2006年2月,研究了石首麋鹿冬季的生境选择。共随机抽取了195个样方,其中石首麋鹿国家级自然保护区内111个,保护区外江南三合垸84个。在样方中测定了食物丰富度、距水源的距离、距林缘距离、距道路的距离、植被类型、距最近居民点的距离6种生境因子。用SPSS软件分别进行卡方检验、主成分分析和相关分析。结果表明:麋鹿选择食物丰富、距水源近且远离人为干扰的开阔生境;影响麋鹿冬季生境选择的3个主成分依次为食物因子、人为干扰因子、水源因子;鹿群大小与各生境因子相关不显著。该结果可为保护和改善石首麋鹿的栖息地提供参考。     

Explaining Geographic Gradients in Winter Selection of Landscapes by Boreal Caribou with Implications under Global Changes in Eastern Canada

Many animal species exhibit broad-scale latitudinal or longitudinal gradients in their response to biotic and abiotic components of their habitat. Although knowing the underlying mechanism of these patterns can be critical to the development of sound measures for the preservation or recovery of endangered species, few studies have yet identified which processes drive the existence of geographical gradients in habitat selection. Using extensive spatial data of broad latitudinal and longitudinal extent, we tested three hypotheses that could explain the presence of geographical gradients in landscape selection of the endangered boreal woodland caribou (Rangifer tarandus caribou) during winter in Eastern Canadian boreal forests: 1) climate-driven selection, which postulates that geographic gradients are surrogates for climatic gradients; 2) road-driven selection, which proposes that boreal caribou adjust their selection for certain habitat classes as a function of proximity to roads; and 3) an additive effect of both roads and climate. Our data strongly supported road-driven selection over climate influences. Thus, direct human alteration of landscapes drives boreal caribou distribution and should likely remain so until the climate changes sufficiently from present conditions. Boreal caribou avoided logged areas two-fold more strongly than burnt areas. Limiting the spread of road networks and accounting for the uneven impact of logging compared to wildfire should therefore be integral parts of any habitat management plan and conservation measures within the range of the endangered boreal caribou. The use of hierarchical spatial models allowed us to explore the distribution of spatially-structured errors in our models, which in turn provided valuable insights for generating alternative hypotheses about processes responsible for boreal caribou distribution.     

吉林黄泥河自然保护区马鹿冬季栖息地选择

2009年12月～2010年1月,在黄泥河自然保护区采用样带法对马鹿冬季栖息地选择进行了研究。共设置了47条样带,调查了72个马鹿利用样方和109个对照样方。结果表明,在黄泥河自然保护区冬季马鹿喜欢选择针阔混交林、食物丰富度和灌丛盖度较高、中等坡度和隐蔽级、远离人为干扰源的生境,避开选择阴坡和针叶林。逻辑斯蒂回归分析揭示坡度、隐蔽级、食物丰富度、坡向、人为干扰距离和林型是影响马鹿栖息地选择的主导因子,灌丛盖度为次要因子。回归模型为:Z=-53.391+0.194×坡度+0.352×隐蔽级+0.5×食物丰富度-0.071×灌丛盖度+1.064×坡向(1)+6.11×坡向(2)+0.004×人为干扰距离+17.305×林型(1)+7.147×林型(2),选择利用概率P(z)=ez/(1+ez),模型正确预测率为94.5%。     

Simulating the Interacting Effects of Intraspecific Variation,Disturbance, and Competition on Climate-Driven Range Shifts in Trees

Climate change is expected to favor shifts in plant distributions; some such shifts are already being observed along elevation gradients. However, the rate of such shifts may be limited by their ability to reach newly suitable areas and by competition from resident species. The degree of local adaptation and genetic variation may also play a role in the interaction between migrants and residents by affecting relative fitness. We used a simulation model to explore the interacting effects of dispersal, fecundity, disturbance, and genetic variation on range-edge dynamics between a pair of demographically similar tree species. Ideal climate for an individual is determined by genotype. The simulated landscape undergoes an 80-year period of climate change in which climate bands shift upslope; subsequently, climate is held constant for 300 years. The presence of a high-elevation competitor caused a significant lag in the range shift of the low-elevation species relative to competition-free scenarios. Increases in fecundity and dispersal distance both helped to speed up the replacement of the high-elevation species by the low-elevation species at their range boundary. While some disturbance scenarios facilitated this transition, frequent canopy disturbance inhibited colonization by removing reproductive adults and led to range contractions in both species. Differences between dispersal scenarios were more pronounced when disturbance was frequent (15 vs. 25 year return interval) and dispersal was limited. When the high-elevation species lacked genetic variation, its range was more-easily invaded by the low-elevation species, while a similar lack of variation in the low-elevation species inhibited colonization—but only when this lack of variation decreased the fitness of the affected species near the range boundary. Our model results support the importance of measuring and including dispersal/fecundity, disturbance type and frequency, and genetic variation when assessing the potential for range shifts and species vulnerability to climate change.