Top predators often have powerful direct effects on prey populations, but whether these direct effects propagate to the base of terrestrial food webs is debated. There are few examples of trophic ...cascades strong enough to alter the abundance and composition of entire plant communities. We show that the introduction of arctic foxes (Alopex lagopus) to the Aleutian archipelago induced strong shifts in plant productivity and community structure via a previously unknown pathway. By preying on seabirds, foxes reduced nutrient transport from ocean to land, affecting soil fertility and transforming grasslands to dwarf shrub/forb-dominated ecosystems.
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1. Longitudinal records of prey selection by 10 adult female sea otters on the Monterey Peninsula, California, from 1983 to 1990 demonstrate extreme inter-individual variation in diet. Variation in ...prey availability cannot explain these differences as the data were obtained from a common spatial-temporal area. 2. Individual dietary patterns persisted throughout our study, thus indicating that they are life-long characteristics. 3. Individual dietary patterns in sea otters appear to be transmitted along matrilines, probably by way of learning during the period of mother-young association. 4. Efficient utilization of different prey types probably requires radically different sensory/motor skills, each of which is difficult to acquire and all of which may exceed the learning and performance capacities of any single individual. This would explain the absence of generalists and inertia against switching, but not the existence of alternative specialists. 5. Such individual variation might arise in a constant environment from frequency-dependent effects, whereby the relative benefit of a given prey specialization depends on the number of other individuals utilizing that prey. Additionally, many of the sea otter's prey fluctuate substantially in abundance through time. This temporal variation, in conjunction with matrilineal transmission of foraging skills, may act to mediate the temporal dynamics of prey specializations. 6. Regardless of the exact cause, such extreme individual variation in diet has broad ramifications for population and community ecology. 7. The published literature indicates that similar patterns occur in many other species.
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This large trial shows that postoperative chemoradiotherapy can increase survival after gastric resection.
The curative treatment of stomach cancer requires gastric resection.
1
However, most ...patients are not cured by this surgery. A review of data from the National Cancer Data Base on 50,169 patients in the United States who underwent gastrectomy between 1985 and 1996 found a 10-year survival rate of 65 percent among patients with stage IA disease (tumor confined to the gastric mucosa), but the 10-year survival rates among those with more advanced disease ranged from 3 percent to 42 percent, depending on the extent of disease.
2
The high rate of relapse after resection makes it important to consider adjuvant treatment . . .
Restore protected status for gray wolves Kareiva, P.; Estes, J. A.; Marvier, M.
Science (American Association for the Advancement of Science),
08/2021, Volume:
373, Issue:
6555
Journal Article
After nearly a century of recovery from overhunting, sea otter populations are in abrupt decline over large areas of western Alaska. Increased killer whale predation is the likely cause of these ...declines. Elevated sea urchin density and the consequent deforestation of kelp beds in the nearshore community demonstrate that the otter's keystone role has been reduced or eliminated. This chain of interactions was probably initiated by anthropogenic changes in the offshore oceanic ecosystem.
Serendipity Estes, James A
2016., 20160517, 2016, 2016-05-17, Volume:
14
eBook
"To newly minted biologist James Estes, the sea otters he was studying in the leafy kelp forests off the coast of Alaska appeared to have an unbalanced relationship with their larger environment. ...Gorging themselves on the sea urchins that grazed among the kelp, these small charismatic mammals seemed to give little back in return. But as Estes dug deeper, he unearthed a far more complex relationship between the otter and its underwater environment, discovering that otters played a critical role in driving positive ecosystem dynamics. While teasing out the connective threads, he began to question our assumptions about ecological relationships. These questions would ultimately inspire a lifelong quest to better understand the surprising complexity of our natural world and the unexpected ways we discover it. Serendipity tells the story of James Estes's life as a naturalist and the concepts that drive his interest in researching the ecological role of large predators. Using the relationship between sea otters, kelp, and sea urchins as a touchstone, Estes retraces his investigations of numerous other species, ecosystems, and ecological processes in an attempt to discover why ecologists can learn so many details about the systems within which they work and yet understand so little about the broader processes that influence those systems. Part memoir, part natural history, and deeply inquisitive, Serendipity will entertain and inform readers as it raises thoughtful questions about our relationship with the natural world."
This unprecedented volume presents a sweeping picture of what we know about the natural history, biology, and ecology of whales in the broad context of the dynamics of ocean ecosystems. Innovative ...and comprehensive, the volume encompasses multiple points of view to consider the total ecological impact of industrial whaling on the world's oceans. Combining empirical research, ecological theory and modeling, and historical data, its chapters present perspectives from ecology, population biology, physiology, genetics, evolutionary history, ocean biogeography, economics, culture, and law, among other disiplines. Throughout, contributors investigate how whaling fundamentally disrupted ocean ecosystems, examine the various roles whales play in food webs, and discuss the continuing ecological chain reactions to the depletion of these large animals. In addition to reviewing what is known of the current and historic whale populations, Whales, Whaling, and Ocean Ecosystems considers how this knowledge will bear on scientific approaches to conservation and whaling in the future and provocatively asks whether it is possible to restore ocean ecosystems to their pre-whaling condition.
Populations of seals, sea lions, and sea otters have sequentially collapsed over large areas of the northern North Pacific Ocean and southern Bering Sea during the last several decades. A bottom-up ...nutritional limitation mechanism induced by physical oceanographic change or competition with fisheries was long thought to be largely responsible for these declines. The current weight of evidence is more consistent with top-down forcing. Increased predation by killer whales probably drove the sea otter collapse and may have been responsible for the earlier pinniped declines as well. We propose that decimation of the great whales by post-World War II industrial whaling caused the great whales' foremost natural predators, killer whales, to begin feeding more intensively on the smaller marine mammals, thus "fishing-down" this element of the marine food web. The timing of these events, information on the abundance, diet, and foraging behavior of both predators and prey, and feasibility analyses based on demographic and energetic modeling are all consistent with this hypothesis.
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Abstract
A stellar occultation by the extreme large-perihelion trans-Neptunian object (541132) Leleākūhonua (also known by the provisional designation of 2015 TG
387
) was predicted by the Lucky Star ...project and observed with the Research and Education Collaborative Occultation Network on 2018 October 20 UT. A single detection and a nearby nondetection provide constraints for the size and albedo. When a circular profile is assumed, the radius is
km, corresponding to a geometric albedo
, for an adopted absolute magnitude of
H
V
= 5.6, typical of other objects in dynamically similar orbits. The occultation also provides a high-precision astrometric constraint.
Populations of sea otters, seals and sea lions have collapsed across much of southwest Alaska over the past several decades. The sea otter decline set off a trophic cascade in which the coastal ...marine ecosystem underwent a phase shift from kelp forests to deforested sea urchin barrens. This interaction in turn affected the distribution, abundance and productivity of numerous other species. Ecological consequences of the pinniped declines are largely unknown. Increased predation by transient (marine mammal-eating) killer whales probably caused the sea otter declines and may have caused the pinniped declines as well. Springer et al. proposed that killer whales, which purportedly fed extensively on great whales, expanded their diets to include a higher percentage of sea otters and pinnipeds following a sharp reduction in great whale numbers from post World War II industrial whaling. Critics of this hypothesis claim that great whales are not now and probably never were an important nutritional resource for killer whales. We used demographic/energetic analyses to evaluate whether or not a predator-prey system involving killer whales and the smaller marine mammals would be sustainable without some nutritional contribution from the great whales. Our results indicate that while such a system is possible, it could only exist under a narrow range of extreme conditions and is therefore highly unlikely.
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