共查询到20条相似文献，搜索用时 0 毫秒
1.
Marine mammals are important sources of food for indigenous residents of northern Alaska. Changing sea ice patterns affect the animals themselves as well as access to them by hunters. Documenting the traditional knowledge of Iñupiaq and Yupik hunters concerning marine mammals and sea ice makes accessible a wide range of information relevant to understanding the ecosystem to which humans belong. We interviewed hunters in 11 coastal villages from the northern Bering Sea to the Beaufort Sea. Hunters reported extensive changes in sea ice and weather that have affected the timing of marine mammal migrations, their distribution and behaviour and the efficacy of certain hunting methods. Amidst these changes, however, hunters cited offsetting technological benefits, such as more powerful and fuel-efficient outboard engines. Other concerns included potential impacts to subsistence hunting from industrial activity such as shipping and oil and gas development. While hunters have been able to adjust to some changes, continued environmental changes and increased disturbance from human activity may further challenge their ability to acquire food in the future. There are indications, however, that innovation and flexibility provide sources of resilience. 相似文献
2.
Global climate warming has caused major reductions in sea ice in the Arctic, posing a serious threat to ice-associated marine mammals. Herein, novel data on birth mass and pup growth rates over a 15-year period (1993–2007; 10 years with growth data) are reported for bearded seals, as well as initial behavioral responses by this species to major, local declines in sea-ice in Svalbard, Norway. In total, 205 pups were captured; 64 of which were recaptured, some repeatedly, producing 85 growth intervals for nursing pups. Average birth mass of pups was 37.1 ± 3.8 (SD) kg (range 33–47 kg, n = 25); birth mass before vs. after the sea ice collapse (2006 onward) were not found to differ. Pups grew at a rate of 3.0 ± 0.7 kg/day (1.8–4.8 kg/day, n = 64) during the nursing period. LME models suggest that ice concentration did not affect the growth rate of pups. Most females shifted from traditional first-year ice floes to glacier-ice pieces for birthing and nursing their young, following the regional sea ice collapse. However, retraction of tidal glaciers will likely eliminate this replacement birthing and nursing habitat for bearded seals in Svalbard in the coming decades. 相似文献
3.
The loss of Arctic sea ice is predicted to open up the Northwest Passage, shortening shipping routes and facilitating the exchange of marine organisms between the Atlantic and the Pacific oceans. Here, we present the first observations of distribution overlap of bowhead whales (Balaena mysticetus) from the two oceans in the Northwest Passage, demonstrating this route is already connecting whales from two populations that have been assumed to be separated by sea ice. Previous satellite tracking has demonstrated that bowhead whales from West Greenland and Alaska enter the ice-infested channels of the Canadian High Arctic during summer. In August 2010, two bowhead whales from West Greenland and Alaska entered the Northwest Passage from opposite directions and spent approximately 10 days in the same area, documenting overlap between the two populations. 相似文献
4.
Meica Valdivia Luciano O. Valenzuela Verónica Berriel Diego Rodríguez Paula Laporta Massimiliano Drago Alessandra Cani Leandro Bergamino 《Marine Mammal Science》2024,40(2):e13077
The study of resource partitioning within a community is central to understanding the processes that enable interspecific competition and coexistence. This study aimed to understand the resource partitioning and habitat preferences among odontocetes in Uruguay. We analyzed stable carbon and nitrogen isotopes data from the bone tissue of common dolphins (Delphinus delphis), Fraser's dolphins (Lagenodelphis hosei), false killer whales (Pseudorca crassidens), Lahille's bottlenose dolphins (Tursiops truncatus gephyreus), Burmeister's porpoises (Phocoena spinipinnis), and franciscana dolphins (Pontoporia blainvillei). Based on the isotopic values, false killer whale individuals were divided into two different ecological groups (ecotype 1 and 2). Isotopic values also suggest that franciscana dolphins, Burmeister's porpoises, Lahille's bottlenose dolphins, and false killer whales ecotype 1 feed on the continental shelf and/or high trophic level preys. At the other end of the gradient, values suggest Fraser's dolphins and false killer whales ecotype 2 use resources from the oceanic environment and/or lower trophic preys. Isotopic niche overlap was found between the common dolphin and Lahille's bottlenose dolphin and between Lahille's bottlenose dolphin and false killer whale ecotype 1. This work provides novel basic information about the trophic habit and feeding habitat of the odontocetes inhabiting one of the most important estuaries of South America. 相似文献
5.
Dorte Krause‐Jensen Núria Marbà Birgit Olesen Mikael K. Sejr Peter Bondo Christensen João Rodrigues Paul E. Renaud Thorsten J.S. Balsby Søren Rysgaard 《Global Change Biology》2012,18(10):2981-2994
We studied the depth distribution and production of kelp along the Greenland coast spanning Arctic to sub‐Arctic conditions from 78 ºN to 64 ºN. This covers a wide range of sea ice conditions and water temperatures, with those presently realized in the south likely to move northwards in a warmer future. Kelp forests occurred along the entire latitudinal range, and their depth extension and production increased southwards presumably in response to longer annual ice‐free periods and higher water temperature. The depth limit of 10% kelp cover was 9–14 m at the northernmost sites (77–78 ºN) with only 94–133 ice‐free days per year, but extended to depths of 21–33 m further south (73 ºN–64 ºN) where >160 days per year were ice‐free, and annual production of Saccharina longicruris and S. latissima, measured as the size of the annual blade, ranged up to sevenfold among sites. The duration of the open‐water period, which integrates light and temperature conditions on an annual basis, was the best predictor (relative to summer water temperature) of kelp production along the latitude gradient, explaining up to 92% of the variation in depth extension and 80% of the variation in kelp production. In a decadal time series from a high Arctic site (74 ºN), inter‐annual variation in sea ice cover also explained a major part (up to 47%) of the variation in kelp production. Both spatial and temporal data sets thereby support the prediction that northern kelps will play a larger role in the coastal marine ecosystem in a warmer future as the length of the open‐water period increases. As kelps increase carbon‐flow and habitat diversity, an expansion of kelp forests may exert cascading effects on the coastal Arctic ecosystem. 相似文献
6.
Inger Greve Alsos Dorothee Ehrich Marit-Solveig Seidenkrantz Ole Bennike Andreas Joachim Kirchhefer Aslaug Geirsdottir 《Biology letters》2016,12(9)
Sea ice has been suggested to be an important factor for dispersal of vascular plants in the Arctic. To assess its role for postglacial colonization in the North Atlantic region, we compiled data on the first Late Glacial to Holocene occurrence of vascular plant species in East Greenland, Iceland, the Faroe Islands and Svalbard. For each record, we reconstructed likely past dispersal events using data on species distributions and genetics. We compared these data to sea-ice reconstructions to evaluate the potential role of sea ice in these past colonization events and finally evaluated these results using a compilation of driftwood records as an independent source of evidence that sea ice can disperse biological material. Our results show that sea ice was, in general, more prevalent along the most likely dispersal routes at times of assumed first colonization than along other possible routes. Also, driftwood is frequently dispersed in regions that have sea ice today. Thus, sea ice may act as an important dispersal agent. Melting sea ice may hamper future dispersal of Arctic plants and thereby cause more genetic differentiation. It may also limit the northwards expansion of competing boreal species, and hence favour the persistence of Arctic species. 相似文献
7.
Killer whales (Orcinus orca) have a global distribution, but many high‐latitude populations are not well studied. We provide a comprehensive review of the history and ecology of killer whales in the Canadian Arctic, for which there has previously been little information. We compiled a database of 450 sightings spanning over 15 decades (1850–2008) to document the historical occurrence, distribution, feeding ecology, and seasonality of killer whales observed throughout the region. Sighting reports per decade increased substantially since 1850 and were most frequent in the eastern Canadian Arctic. The mean reported group size was 8.3 (median = 4, range 1–100), but size varied significantly among regions and observed prey types. Observations of predation events indicate that Canadian Arctic killer whales prey upon other marine mammals. Monodontids were the most frequently observed prey items, followed by bowhead whales (Balaena mysticetus), phocids, and groups of mixed mammal prey. No killer whale sightings occurred during winter, with sightings gradually increasing from early spring to a peak in summer, after which sightings gradually decreased. Our results suggest that killer whales are established, at least seasonally, throughout the Canadian Arctic, and we discuss potential ecological implications of increased presence with declining sea ice extent and duration. 相似文献
8.
Mónica Y. Rodríguez‐Pérez David Aurioles‐Gamboa Laura Sánchez‐Velásco Seth D. Newsome 《Marine Mammal Science》2018,34(3):790-805
The vaquita (Phocoena sinus) is the world's most endangered cetacean and has experienced a 60% reduction in the size of its population in the past decade. Knowledge of its basic ecology is essential for developing successful management plans to protect and conserve this species. In this study, we identified vaquita foraging areas by creating an isoscape of the Upper Gulf of California (UGC) based on sediment and zooplankton carbon (δ13C) and nitrogen (δ15N) isotope values. Our results confirm that this species is confined to the western region of the UGC, which is characterized by relatively high δ15N values (sediments: 10.2‰ ± 2.0‰, zooplankton: 15.8‰ ± 1.3‰), higher sea surface temperatures (～16°C–25°C), higher concentrations of silt in sediments, and the highest turbidity. In contrast, the eastern region of the UGC had relatively low sediment (7.7‰ ± 2.4‰) and zooplankton (14.6‰ ± 1.0‰) δ15N values, and the highest concentrations of sand in sediments. Our approach is an effective use of marine isoscapes over a small spatial scale (<200 km) to identify the environmental characteristics that define the critical habitat for an extremely endangered marine mammal. 相似文献
9.
MASS ESTIMATES USING BODY MORPHOLOGY IN STELLER SEA LIONS 总被引：2，自引：0，他引：2
Abstract: Analytical procedures developed from studies on phocids for relating body morphometrics (length and girth) to mass were applied to 390 Steller sea lions from the Gulf of Alaska and the Bering Sea. The equations relating body volume to mass were significant and had very high correlation coefficients for animals from about 60 to over 900 kg with a standard error of ±0.6% in fitted mass. There was a significant difference in these relationships for female sea lions studied in the 1970s and those examined in the 1980s. The latter sea lions were smaller and/or leaner than those collected in the 1970s. 相似文献
10.
Stable isotope analysis (SIA) has emerged as a common tool in ecology and has proven especially useful in the study of animal diet, habitat use, movement, and physiology. SIA has been vigorously applied to the study of marine mammals, because most species live in habitats or undergo large migrations/movements that make them difficult to observe. Our review supplies a complete list of published SIA contributions to marine mammal science and highlights informative case examples in four general research areas: (1) physiology and fractionation, (2) foraging ecology and habitat use, (3) ecotoxicology, and (4) historic ecology and paleoecology. We also provide a condensed background of isotopic nomenclature, highlight several physiological considerations important for accurate interpretation of isotopic data, and identify research areas ripe for future growth. Because it is impossible to conduct controlled laboratory experiments on most marine mammal species, future studies in marine mammal ecology must draw on isotopic data collected from other organisms and be cognizant of key assumptions often made in the application of SIA to the study of animal ecology. The review is designed to be accessible to all audiences, from students unfamiliar with SIA to those who have utilized it in published studies. 相似文献
11.
Climate warming is causing unidirectional changes to annual patterns of sea ice distribution, structure, and freeze‐up. We summarize evidence that documents how loss of sea ice, the primary habitat of polar bears (Ursus maritimus), negatively affects their long‐term survival. To maintain viable subpopulations, polar bears depend on sea ice as a platform from which to hunt seals for long enough each year to accumulate sufficient energy (fat) to survive periods when seals are unavailable. Less time to access to prey, because of progressively earlier breakup in spring, when newly weaned ringed seal (Pusa hispida) young are available, results in longer periods of fasting, lower body condition, decreased access to denning areas, fewer and smaller cubs, lower survival of cubs as well as bears of other age classes and, finally, subpopulation decline toward eventual extirpation. The chronology of climate‐driven changes will vary between subpopulations, with quantifiable negative effects being documented first in the more southerly subpopulations, such as those in Hudson Bay or the southern Beaufort Sea. As the bears' body condition declines, more seek alternate food resources so the frequency of conflicts between bears and humans increases. In the most northerly areas, thick multiyear ice, through which little light penetrates to stimulate biological growth on the underside, will be replaced by annual ice, which facilitates greater productivity and may create habitat more favorable to polar bears over continental shelf areas in the short term. If the climate continues to warm and eliminate sea ice as predicted, polar bears will largely disappear from the southern portions of their range by mid‐century. They may persist in the northern Canadian Arctic Islands and northern Greenland for the foreseeable future, but their long‐term viability, with a much reduced global population size in a remnant of their former range, is uncertain. 相似文献
12.
Jill A. Olin Patricia A. Fair Melissa A. Recks Eric Zolman Jeff Adams Aaron T. Fisk 《Marine Mammal Science》2012,28(1):E28-E40
Using photo‐identification data, bottlenose dolphin (Tursiops truncatus) populations can be differentiated based on their use of particular estuaries or coastal habitats. Questions remain, however, about the validity of such fine‐scale population partitioning and whether the resulting assemblages utilize unique forage bases. To address the issue of forage base use, stable isotopes of carbon (δ13C), nitrogen (δ15N) and sulfur (δ34S) were analyzed from skin tissues (n= 74) of bottlenose dolphins sampled seasonally along the coast and in three estuaries near Charleston, South Carolina. Autumn values of δ34S, δ15N, and δ13C and summer values of δ34S indicated that dolphins sampled from these four assemblages utilized unique forage bases, despite limited sample sizes. Likewise, autumn and spring differences in δ15N and δ13C values were evident in the North Edisto River, and in δ34S from dolphins sampled from all three estuarine assemblages; no seasonal differences were identified in the coastal assemblage. Results demonstrate the importance of considering spatial and temporal variation in forage base when developing local management plans for bottlenose dolphin and highlight the discriminatory power of δ34S for estuarine and coastal marine mammals. These results also suggest that stable isotopes could be developed as a complementary tool for photo‐identification based partitioning of bottlenose dolphin populations. 相似文献
13.
Jakob J. Assmann Isla H. Myers‐Smith Albert B. Phillimore Anne D. Bjorkman Richard E. Ennos Janet S. Prevy Greg H. R. Henry Niels M. Schmidt Robert D. Hollister 《Global Change Biology》2019,25(7):2258-2274
The Arctic is undergoing dramatic environmental change with rapidly rising surface temperatures, accelerating sea ice decline and changing snow regimes, all of which influence tundra plant phenology. Despite these changes, no globally consistent direction of trends in spring phenology has been reported across the Arctic. While spring has advanced at some sites, spring has delayed or not changed at other sites, highlighting substantial unexplained variation. Here, we test the relative importance of local temperatures, local snow melt date and regional spring drop in sea ice extent as controls of variation in spring phenology across different sites and species. Trends in long‐term time series of spring leaf‐out and flowering (average span: 18 years) were highly variable for the 14 tundra species monitored at our four study sites on the Arctic coasts of Alaska, Canada and Greenland, ranging from advances of 10.06 days per decade to delays of 1.67 days per decade. Spring temperatures and the day of spring drop in sea ice extent advanced at all sites (average 1°C per decade and 21 days per decade, respectively), but only those sites with advances in snow melt (average 5 days advance per decade) also had advancing phenology. Variation in spring plant phenology was best explained by snow melt date (mean effect: 0.45 days advance in phenology per day advance snow melt) and, to a lesser extent, by mean spring temperature (mean effect: 2.39 days advance in phenology per °C). In contrast to previous studies examining sea ice and phenology at different spatial scales, regional spring drop in sea ice extent did not predict spring phenology for any species or site in our analysis. Our findings highlight that tundra vegetation responses to global change are more complex than a direct response to warming and emphasize the importance of snow melt as a local driver of tundra spring phenology. 相似文献
14.
Timothy J. Caldwell Sudeep Chandra Karly Feher James B. Simmons Zeb Hogan 《Global Change Biology》2020,26(10):5475-5491
Climate warming has yielded earlier ice break‐up dates in recent decades for lakes leading to water temperature increases, altered habitat, and both increases and decreases to ecosystem productivity. Within lakes, the effect of climate warming on secondary production in littoral and pelagic habitats remains unclear. The intersection of changing habitat productivity and warming water temperatures on salmonids is important for understanding how climate warming will impact mountain ecosystems. We develop and test a conceptual model that expresses how earlier ice break‐up dates influence within lake habitat production, water temperatures and the habitat utilized by, resources obtained and behavior of salmonids in a mountain lake. We measured zoobenthic and zooplankton production from the littoral and pelagic habitats, thermal conditions, and the habitat use, resource use, and fitness of Brook Trout (Salvelinus fontinalis). We show that earlier ice break‐up conditions created a \"resource‐rich\" littoral–benthic habitat with increases in zoobenthic production compared to the pelagic habitat which decreased in zooplankton production. Despite the increases in littoral–benthic food resources, trout did not utilize littoral habitat or zoobenthic resources due to longer durations of warm water temperatures in the littoral zone. In addition, 87% of their resources were supported by the pelagic habitat during periods with earlier ice break‐up when pelagic resources were least abundant. The decreased reliance on littoral–benthic resources during earlier ice break‐up caused reduced fitness (mean reduction of 12 g) to trout. Our data show that changes to ice break‐up drive multi‐directional results for resource production within lake habitats and increase the duration of warmer water temperatures in food‐rich littoral habitats. The increased duration of warmer littoral water temperatures reduces the use of energetically efficient habitats culminating in decreased trout fitness. 相似文献
15.
Andrew L. Von Duyke David C. Douglas Jason K. Herreman Justin A. Crawford 《Ecology and evolution》2020,10(12):5595-5616
Continued Arctic warming and sea‐ice loss will have important implications for the conservation of ringed seals, a highly ice‐dependent species. A better understanding of their spatial ecology will help characterize emerging ecological trends and inform management decisions. We deployed satellite transmitters on ringed seals in the summers of 2011, 2014, and 2016 near Utqia?vik (formerly Barrow), Alaska, to monitor their movements, diving, and haul‐out behavior. We present analyses of tracking and dive data provided by 17 seals that were tracked until at least January of the following year. Seals mostly ranged north of Utqia?vik in the Beaufort and Chukchi Seas during summer before moving into the southern Chukchi and Bering Seas during winter. In all seasons, ringed seals occupied a diversity of habitats and spatial distributions, from near shore and localized, to far offshore and wide‐ranging in drifting sea ice. Continental shelf waters were occupied for >96% of tracking days, during which repetitive diving (suggestive of foraging) primarily to the seafloor was the most frequent activity. From mid‐summer to early fall, 12 seals made ~1‐week forays off‐shelf to the deep Arctic Basin, most reaching the retreating pack‐ice, where they spent most of their time hauled out. Diel activity patterns suggested greater allocation of foraging efforts to midday hours. Haul‐out patterns were complementary, occurring mostly at night until April‐May when midday hours were preferred. Ringed seals captured in 2011—concurrent with an unusual mortality event that affected all ice‐seal species—differed morphologically and behaviorally from seals captured in other years. Speculations about the physiology of molting and its role in energetics, habitat use, and behavior are discussed; along with possible evidence of purported ringed seal ecotypes. 相似文献
16.
Stephen R. Wing James J. Leichter Lucy C. Wing Dale Stokes Sal J. Genovese Rebecca M. McMullin Olya A. Shatova 《Global Change Biology》2018,24(8):3642-3653
Organic matter produced by the sea ice microbial community (SIMCo) is an important link between sea ice dynamics and secondary production in near‐shore food webs of Antarctica. Sea ice conditions in McMurdo Sound were quantified from time series of MODIS satellite images for Sept. 1 through Feb. 28 of 2007–2015. A predictable sea ice persistence gradient along the length of the Sound and evidence for a distinct change in sea ice dynamics in 2011 were observed. We used stable isotope analysis (δ13C and δ15N) of SIMCo, suspended particulate organic matter (SPOM) and shallow water (10–20 m) macroinvertebrates to reveal patterns in trophic structure of, and incorporation of organic matter from SIMCo into, benthic communities at eight sites distributed along the sea ice persistence gradient. Mass‐balance analysis revealed distinct trophic architecture among communities and large fluxes of SIMCo into the near‐shore food web, with the estimates ranging from 2 to 84% of organic matter derived from SIMCo for individual species. Analysis of patterns in density, and biomass of macroinvertebrate communities among sites allowed us to model net incorporation of organic matter from SIMCo, in terms of biomass per unit area (g/m2), into benthic communities. Here, organic matter derived from SIMCo supported 39 to 71 per cent of total biomass. Furthermore, for six species, we observed declines in contribution of SIMCo between years with persistent sea ice (2008–2009) and years with extensive sea ice breakout (2012–2015). Our data demonstrate the vital role of SIMCo in ecosystem function in Antarctica and strong linkages between sea ice dynamics and near‐shore secondary productivity. These results have important implications for our understanding of how benthic communities will respond to changes in sea ice dynamics associated with climate change and highlight the important role of shallow water macroinvertebrate communities as sentinels of change for the Antarctic marine ecosystem. 相似文献
17.
Sveinn A. Hanssen Børge Moe Bård‐Jørgen Bårdsen Frank Hanssen Geir W. Gabrielsen 《Ecology and evolution》2013,3(10):3554-3564
Anthropogenic impact on the environment and wildlife are multifaceted and far‐reaching. On a smaller scale, controlling for predators has been increasing the yield from local natural prey resources. Globally, human‐induced global warming is expected to impose severe negative effects on ecosystems, an effect that is expected to be even more pronounced in the scarcely populated northern latitudes. The clearest indication of a changing Arctic climate is an increase in both air and ocean temperatures leading to reduced sea ice distribution. Population viability is for long‐lived species dependent on adult survival and recruitment. Predation is the main mortality cause in many bird populations, and egg predation is considered the main cause of reproductive failure in many birds. To assess the effect of predation and climate, we compared population time series from a natural experiment where a trapper/down collector has been licensed to actively protect breeding common eiders Somateria mollissima (a large seaduck) by shooting/chasing egg predators, with time series from another eider colony located within a nature reserve with no manipulation of egg predators. We found that actively limiting predator activity led to an increase in the population growth rate and carrying capacity with a factor of 3–4 compared to that found in the control population. We also found that population numbers were higher in years with reduced concentration of spring sea ice. We conclude that there was a large positive impact of human limitation of egg predators, and that this lead to higher population growth rate and a large increase in size of the breeding colony. We also report a positive effect of warming climate in the high arctic as reduced sea‐ice concentrations was associated with higher numbers of breeding birds. 相似文献
18.
近年来随着北极地区的开放和全球变化对北极地区生态环境和海冰现存量的影响日益显现,北极浮冰生态学研究得到了广泛的重视和实质性的进展.最新研究结果显示,浮冰本身包含了一个复杂的生物群落,高纬度浮冰生物群落的初级产量远高于原先的估算,浮冰生物群落在北极海洋生态系统中的作用被进一步确认.但由于对浮冰生物群落的研究受后勤保障条件的制约,目前尚有大量科学问题有待今后进一步深入研究,预期我国科学家将在其中做出贡献. 相似文献
19.
David J. Yurkowski Steve Ferguson Emily S. Choy Lisa L. Loseto Tanya M. Brown Derek C. G. Muir Christina A. D. Semeniuk Aaron T. Fisk 《Ecology and evolution》2016,6(6):1666-1678
Individual specialization (IS), where individuals within populations irrespective of age, sex, and body size are either specialized or generalized in terms of resource use, has implications on ecological niches and food web structure. Niche size and degree of IS of near‐top trophic‐level marine predators have been little studied in polar regions or with latitude. We quantified the large‐scale latitudinal variation of population‐ and individual‐level niche size and IS in ringed seals (Pusa hispida) and beluga whales (Delphinapterus leucas) using stable carbon and nitrogen isotope analysis on 379 paired ringed seal liver and muscle samples and 124 paired beluga skin and muscle samples from eight locations ranging from the low to high Arctic. We characterized both within‐ and between‐individual variation in predator niche size at each location as well as accounting for spatial differences in the isotopic ranges of potential prey. Total isotopic niche width (TINW) for populations of ringed seals and beluga decreased with increasing latitude. Higher TINW values were associated with greater ecological opportunity (i.e., prey diversity) in the prey fish community which mainly consists of Capelin (Mallotus villosus) and Sand lance (Ammodytes sp.) at lower latitudes and Arctic cod (Boreogadus saida) at high latitudes. In beluga, their dietary consistency between tissues also known as the within‐individual component (WIC) increased in a near 1:1 ratio with TINW (slope = 0.84), suggesting dietary generalization, whereas the slope (0.18) of WIC relative to TINW in ringed seals indicated a high degree of individual specialization in ringed seal populations with higher TINWs. Our findings highlight the differences in TINW and level of IS for ringed seals and beluga relative to latitude as a likely response to large‐scale spatial variation in ecological opportunity, suggesting species‐specific variation in dietary plasticity to spatial differences in prey resources and environmental conditions in a rapidly changing ecosystem. 相似文献