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Williams TM, Estes JA, Doak DF, Springer AM. KILLER APPETITES: ASSESSING THE ROLE OF PREDATORS IN ECOLOGICAL COMMUNITIES. Ecology 2004. [DOI: 10.1890/03-0696] [Citation(s) in RCA: 188] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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52
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Golet GH, Schmutz JA, Irons DB, Estes JA. DETERMINANTS OF REPRODUCTIVE COSTS IN THE LONG-LIVED BLACK-LEGGED KITTIWAKE: A MULTIYEAR EXPERIMENT. ECOL MONOGR 2004. [DOI: 10.1890/02-4029] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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53
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Springer AM, Estes JA, van Vliet GB, Williams TM, Doak DF, Danner EM, Forney KA, Pfister B. Sequential megafaunal collapse in the North Pacific Ocean: an ongoing legacy of industrial whaling? Proc Natl Acad Sci U S A 2003; 100:12223-8. [PMID: 14526101 PMCID: PMC218740 DOI: 10.1073/pnas.1635156100] [Citation(s) in RCA: 157] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
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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Monson DH, Estes JA, Bodkin JL, Siniff DB. Life history plasticity and population regulation in sea otters. OIKOS 2003. [DOI: 10.1034/j.1600-0706.2000.900304.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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55
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56
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Gelatt TS, Siniff DB, Estes JA. Activity Patterns and Time Budgets of the Declining Sea Otter Population at Amchitka Island, Alaska. J Wildl Manage 2002. [DOI: 10.2307/3802868] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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58
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59
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Jackson JB, Kirby MX, Berger WH, Bjorndal KA, Botsford LW, Bourque BJ, Bradbury RH, Cooke R, Erlandson J, Estes JA, Hughes TP, Kidwell S, Lange CB, Lenihan HS, Pandolfi JM, Peterson CH, Steneck RS, Tegner MJ, Warner RR. Historical overfishing and the recent collapse of coastal ecosystems. Science 2001; 293:629-37. [PMID: 11474098 DOI: 10.1126/science.1059199] [Citation(s) in RCA: 1686] [Impact Index Per Article: 73.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Ecological extinction caused by overfishing precedes all other pervasive human disturbance to coastal ecosystems, including pollution, degradation of water quality, and anthropogenic climate change. Historical abundances of large consumer species were fantastically large in comparison with recent observations. Paleoecological, archaeological, and historical data show that time lags of decades to centuries occurred between the onset of overfishing and consequent changes in ecological communities, because unfished species of similar trophic level assumed the ecological roles of overfished species until they too were overfished or died of epidemic diseases related to overcrowding. Retrospective data not only help to clarify underlying causes and rates of ecological change, but they also demonstrate achievable goals for restoration and management of coastal ecosystems that could not even be contemplated based on the limited perspective of recent observations alone.
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Williams TM, Noren D, Berry P, Estes JA, Allison C, Kirtland J. The diving physiology of bottlenose dolphins (Tursiops truncatus). III. Thermoregulation at depth. J Exp Biol 1999; 202:2763-9. [PMID: 10504312 DOI: 10.1242/jeb.202.20.2763] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
During diving, marine mammals initiate a series of cardiovascular changes that include bradycardia and decreased peripheral circulation. Because heat transfer from thermal windows located in peripheral sites of these mammals depends on blood flow, such adjustments may limit their thermoregulatory capabilities during submergence. Here, we demonstrate how the thermoregulatory responses of bottlenose dolphins (Tursiops truncatus) are coordinated with the diving response. Heart rate, skin temperature and heat transfer from the dorsal fin and flank were measured while dolphins rested on the water surface, stationed 5–50 m under water and floated at the surface immediately following a dive. The results showed that heat flow ranged from 42.9+/−7.3 to 126.2+/−23.1 W m(−)(2) and varied with anatomical site and diving activity. Upon submergence, heat flow declined by 35 % from the dorsal fin and by 24 % from the flank. An immediate increase in heat flow to levels exceeding pre-dive values occurred at both sites upon resurfacing. Changes in heart rate during diving paralleled the thermoregulatory responses. Mean pre-dive heart rate (102.0+/−2.6 beats min(−)(1), N=26) decreased by 63.4 % during dives to 50 m and immediately returned to near resting levels upon resurfacing. These studies indicate that heat dissipation by dolphins is attenuated during diving. Rather than challenge the diving response, heat transfer is delayed until post-dive periods when the need for oxygen conservation is reduced.
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61
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Estes JA, Tinker MT, Williams TM, Doak DF. Killer whale predation on sea otters linking oceanic and nearshore ecosystems. Science 1998; 282:473-6. [PMID: 9774274 DOI: 10.1126/science.282.5388.473] [Citation(s) in RCA: 429] [Impact Index Per Article: 16.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
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.
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62
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Estes JA, Kruuk H. Wild Otters, Predation and Populations. J Wildl Manage 1997. [DOI: 10.2307/3802216] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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63
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Power ME, Tilman D, Estes JA, Menge BA, Bond WJ, Mills LS, Daily G, Castilla JC, Lubchenco J, Paine RT. Challenges in the Quest for Keystones. Bioscience 1996. [DOI: 10.2307/1312990] [Citation(s) in RCA: 1217] [Impact Index Per Article: 43.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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64
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Stern JL, Hagerman AE, Steinberg PD, Winter FC, Estes JA. A new assay for quantifying brown algal phlorotannins and comparisons to previous methods. J Chem Ecol 1996; 22:1273-93. [DOI: 10.1007/bf02266965] [Citation(s) in RCA: 84] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/1995] [Accepted: 03/04/1996] [Indexed: 11/24/2022]
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65
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Power ME, Tilman D, Carpenter SR, Huntly N, Leibold M, Morin P, Menge BA, Estes JA, Ehrlich PR, Hixon M, Lodge DM, McPeek MA, Fauth JE, Reznick D, Crowder LB, Holbrook SJ, Peckarsky BL, Gill DE, Antonovics J, Polis GA, Wake DB, Orians G, Ketterson ED, Marschall E, Lawler SP. The Role of Experiments in Ecology. Science 1995. [DOI: 10.1126/science.270.5236.561.a] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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66
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Steinberg PD, Estes JA, Winter FC. Evolutionary consequences of food chain length in kelp forest communities. Proc Natl Acad Sci U S A 1995; 92:8145-8. [PMID: 11607573 PMCID: PMC41112 DOI: 10.1073/pnas.92.18.8145] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Kelp forests are strongly influenced by macroinvertebrate grazing on fleshy macroalgae. In the North Pacific Ocean, sea otter predation on macroinvertebrates substantially reduces the intensity of herbivory on macroalgae. Temperate Australasia, in contrast, has no known predator of comparable influence. These ecological and biogeographic patterns led us to predict that (i) the intensity of herbivory should be greater in temperate Australasia than in the North Pacific Ocean; thus (ii) Australasian seaweeds have been under stronger selection to evolve chemical defenses and (iii) Australasian herbivores have been more strongly selected to tolerate these compounds. We tested these predictions first by measuring rates of algal tissue loss to herbivory at several locations in Australasian and North Pacific kelp forests. There were significant differences in grazing rates among sea otter-dominated locations in the North Pacific (0-2% day-1), Australasia (5-7% day-1), and a North Pacific location lacking sea otters (80% day-1). The expectations that chronically high rates of herbivory in Australasia have selected for high concentrations of defensive secondary metabolites (phlorotannins) in brown algae and increased tolerance of these defenses in the herbivores also were supported. Phlorotannin concentrations in kelps and fucoids from Australasia were, on average, 5-6 times higher than those in a comparable suite of North Pacific algae, confirming earlier findings. Furthermore, feeding rates of Australasian herbivores were largely unaffected by phlorotannins, regardless of the compounds' regional source. North Pacific herbivores, in contrast, were consistently deterred by phlorotannins from both Australasia and the North Pacific. These findings suggest that top-level consumers, acting through food chains of various lengths, can strongly influence the ecology and evolution of plantherbivore interactions.
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67
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Estes JA, Duggins DO. Sea Otters and Kelp Forests in Alaska: Generality and Variation in a Community Ecological Paradigm. ECOL MONOGR 1995. [DOI: 10.2307/2937159] [Citation(s) in RCA: 518] [Impact Index Per Article: 17.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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68
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Riedman ML, Estes JA, Staedler MM, Giles AA, Carlson DR. Breeding Patterns and Reproductive Success of California Sea Otters. J Wildl Manage 1994. [DOI: 10.2307/3809308] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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69
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70
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Li L, Wang HK, Fujioka T, Chang JJ, Kozuka M, Konoshima T, Estes JA, McPhail DR, McPhail AT, Lee KH. Structure and stereochemistry of amorphispironone, a novel cytotoxic spironone type rotenoid from Amorpha fruticosa. ACTA ACUST UNITED AC 1991. [DOI: 10.1039/c39910001652] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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71
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72
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73
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Duggins DO, Simenstad CA, Estes JA. Magnification of Secondary Production by Kelp Detritus in Coastal Marine Ecosystems. Science 1989; 245:170-3. [PMID: 17787876 DOI: 10.1126/science.245.4914.170] [Citation(s) in RCA: 181] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Kelps are highly productive seaweeds found along most temperate latitude coastlines, but the fate and importance of kelp production to nearshore ecosystems are largely unknown. The trophic role of kelp-derived carbon in a wide range of marine organisms was assessed by a natural experiment. Growth rates of benthic suspension feeders were greatly increased in the presence of organic detritus (particulate and dissolved) originating from large benthic seaweeds (kelps). Stable carbon isotope analysis confirmed that kelp-derived carbon is found throughout the nearshore food web.
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74
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Abstract
Although rarely reported in the past, predation by sea otters (Enhydra lutris) on seabirds has been observed more frequently in the last decade. A total of 23 incidents of definite or probable predation on seabirds have been observed in California (20) and in Alaska at Amchitka Island (3). In California, the most commonly eaten species were western grebes, although cormorants, gulls, common loons, and surf scoters were also consumed. All cases of seabird predation in California have occurred in the northern part of the sea otter's range in three locations: Point Lobos, Stillwater Cove, and the Monterey harbor area. When sex could be determined, most of the otters observed feeding on seabirds were adult males. At one site, it appeared that the same individual repeatedly captured birds. Predation on seabirds is indicative of the sea otter's ability to learn new and innovative foraging tactics, and is consistent with a high degree of individual variation in diet observed among sea otters in Monterey. Sea otters initially capture birds by diving and grabbing them from underwater while the bird rests on the surface, in a manner similar to that employed by coastal river otters to capture seabirds. When mink, freshwater-inhabiting otters, and sea otters are compared, a graded reduction in the tendency to eat birds appears to occur in the more aquatic mustelids, with the relative importance of birds in the diet being greatest in mink and least in sea otters.
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75
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Estes JA, Jameson RJ. A Double-Survey Estimate for Sighting Probability of Sea Otters in California. J Wildl Manage 1988. [DOI: 10.2307/3801061] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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76
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Irons DB, Anthony RG, Estes JA. Foraging Strategies of Glaucous-Winged Gulls in a Rocky Intertidal Community. Ecology 1986. [DOI: 10.2307/1939077] [Citation(s) in RCA: 62] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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77
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Estes JA, Underwood KE, Karmann MJ. Activity-Time Budgets of Sea Otters in California. J Wildl Manage 1986. [DOI: 10.2307/3800973] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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78
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Estes JA. Riverine Mammals: Otters. Science 1986; 233:1333-4. [PMID: 17843364 DOI: 10.1126/science.233.4770.1333-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
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79
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Estes JA, Jameson RJ, Rhode EB. Activity and Prey Election in the Sea Otter: Influence of Population Status on Community Structure. Am Nat 1982. [DOI: 10.1086/283985] [Citation(s) in RCA: 66] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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80
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81
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Abstract
The importance of marine mammals as predators to the organization of marine communities is poorly known, although in several structurally analogous systems the ecological and evolutionary roles of predators are known to be of considerable importance. Occupation of the marine environment by mammals probably carried physiological constraints for single-young pregnancies thereby limiting all species to low intrinsic rates of population increase. As such, species subjected to high mortality rates from predation or other natural disturbances became extinct; those that survived probably were largely resource limited. In view of this scenario it is suggested that stable populations of marine mammals can be maintained at high levels without being manipulated in most communities. Exploitation probably constitutes a rather dramatic environmental change to marine mammals consequently subjecting them to selective forces fundamentally different from many of those under the influence of which they evolved. Key words: community structure, evolution, exploitation, fitness, life history, marine mammal, predation, resource limitation
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82
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Estes JA, Gilbert JR. Evaluation of an Aerial Survey of Pacific Walruses (Odobenus rosmarus divergens). ACTA ACUST UNITED AC 1978. [DOI: 10.1139/f78-178] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
An aerial survey of Pacific walruses (Odobenus rosmarus divergens) was evaluated to determine the reliability of estimates of population abundance. The probability of detecting groups of walruses on the pack ice remained uniform to at least 0.93 km from the flight line, whereas the probability of detection decreased significantly beyond 0.23 km for walruses in the water. Walruses were more abundant along the ice-edge zone between 162 and 165°W than in other areas of the Chukchi Sea during September 1975. Few walruses were observed in consolidated pack ice north of the ice-edge zone or in ice-free water to the south. More walrus groups and larger mean group size were observed on September 8 than on other days. We estimated abundance for each day and all days combined using methods based on sample area and numbers of strip samples. Estimates varied among days by over an order of magnitude; this variation is attributed to the combined effect of chance sampling of an aggregated population and variation in the fraction of walruses hauled out. The coefficient of variation of the estimates ranged between 0.25 and 0.99. This imprecision was due to the aggregated distribution of walruses and the large variation in group size. Using the survey data as a basis for stratification, we calculated that, due to the high variability within strata, a sample size of 40% of the total area or 56% of the total available strips would be required to obtain 95% confidence limits within 10% of the estimate of total abundance. Variation contributed by observer error in estimating group size also is relatively unimportant to the precision of abundance estimates. Studies of natural history, particularly those oriented toward activity and habitat selection, would help investigators estimate bias due to the variable fraction hauled out and design surveys based on meaningful strata. Estimates of total abundance based on limited survey efforts will provide information of little reliability. Key words: aerial survey, aggregation, Chukchi Sea, estimation, population, stratification, walrus
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Abstract
Reexamination of stratified faunal components of a prehistoric Aleut midden excavated on Amchitka Island, Alaska, indicates that Aleut prey items changed dramatically during 2500 years of aboriginal occupation. Recent ecological studies in the Aleutian Islands have shown the concurrent existence of two alternate stable nearshore communities, one dominated by macroalgae, the other by epibenthic herbivores, which are respectively maintained by the presence or absence of dense sea otter populations. Thus, rather than cultural shifts in food preference, the changes in Aleut prey were probably the result of local overexploitation of sea otters by aboriginal Aleuts.
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84
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85
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Buss IO, Estes JA. The functional significance of movements and positions of the pinnae of the African elephant, Loxodonta africana. J Mammal 1971; 52:21-7. [PMID: 5545560] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
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