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  • 2000-2004
  • 1995-1999  (6)
  • 1955-1959
  • habitat use  (3)
  • methyl mercury  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Long-Term Habitat Use by Mountain Gorillas (Gorilla gorilla beringei). 1. Consistency, Variation, and Home Range Size and Stability (1998)
    Springer
    International journal of primatology 19 (1998), S. 651-680 
    Details
    ISSN: 1573-8604
    Keywords: mountain gorillas ; habitat use ; area occupation ; food distribution ; home range ; scramble competition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mountain gorillas are highly folivorous. Food is abundant and perennially available in much of their habitat. Still, limited research has shown that single gorilla groups heavily used areas where food biomass and quality were relatively high and where they met daily nutritional needs with relatively low foraging effort. Also, ecological factors influenced solitary males less than groups with females. Long-term data on habitat use by multiple mountain gorilla social units and more extensive data on variation in food distribution, presented here, confirm that food distribution influences areal occupation densities across groups and over time. These data also confirm the group/solitary male distinction and show that food distribution became more important for one male once he acquired females. Groups used ≤25 km 2 , and inter-annual home range and core area overlap was often low. Annual home range and core area size varied considerably within groups and across years. It bore no simple relationship to group size and estimated group biomass. Core areas were biased samples of total home ranges and were relatively good foraging areas. One group abruptly shifted its home range in response to male mating competition. Home ranges of two others expanded from 1981 to 1987, though at a decreasing rate. Data on one such group, which varied considerably in size, are consistent with arguments that costs of scramble competition are low except in unusually large groups. Low site fidelity, low scramble costs, and high home range overlap should decrease the ecological costs of female transfer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020324909101
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Long-Term Habitat Use by Mountain Gorillas (Gorilla gorilla beringei). 2. Reuse of Foraging Areas in Relation to Resource Abundance, Quality, and Depletion (1998)
    Springer
    International journal of primatology 19 (1998), S. 681-702 
    Details
    ISSN: 1573-8604
    Keywords: mountain gorillas ; habitat use ; foraging strategy ; resource depletion ; cropping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Resource depression caused by current feeding and the rate of resource renewal should influence foragers' decisions about when to revisit foraging areas. Adjustment of foraging paths and revisit rates should be particularly important when resources renew slowly. Foragers can also benefit by returning more often to highly profitable than to less profitable foraging areas. Many highly frugivorous primates seem to time revisits to fruit sources so as to harvest fruit efficiently and, also, use efficient search paths. Fewer data on non-frugivores exist. Mountain gorillas are folivores that eat mostly perennially available, continuously growing herbs and vines. Vegetation regenerates slowly from the effects of gorilla trampling, though trampling can also facilitate food species productivity, at least in the short term. Adjustment of intervals between visits to foraging areas to the extent of previous use and to resource renewal rates should increase gorilla foraging efficiency. Long-term data on habitat use by 6 mountain gorilla social units show that revisit intervals vary in association with variation in the extent of previous use and in plant productivity. However, they also revisit areas more often, the higher the biomass and nutritional quality of food there. These data are generally consistent with the hypothesis that the gorillas crop resources on a sustained-yield basis, though more precise data on areal revisits and complementary long-term data on vegetation composition would be needed to test the hypothesis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020376925939
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Seasonality in the Ecology and Life Histories of Mountain Gorillas (Gorilla gorilla beringei) (1998)
    Springer
    International journal of primatology 19 (1998), S. 929-948 
    Details
    ISSN: 1573-8604
    Keywords: gorillas ; seasonality ; diet ; habitat use ; mortality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The abundance of food, especially that of fruit and often that of young leaves, varies considerably over time for most primates. This variation can depend on or be independent of seasonality in rainfall. Mountain gorillas (Gorilla gorilla beringei) in the Virungas are exceptional: their habitat contains almost no edible fruit, and they mostly eat perennially available herbs and vines that are densely and evenly distributed in much of their habitat. Earlier studies documented little consistent temporal variation in mountain gorilla diets and habitat use, except for seasonal use of bamboo by some groups, and documented no birth seasonality. Long-term data (≤ 7 years) on 6 mountain gorilla groups confirm these results for habitat use, except that they show some seasonality in use of the upper altitudinal extremes of the gorillas' home ranges for unclear reasons. Relatively low and inconsistent variation in habitat quality over time should lower the costs of grouping for gorillas compared to other apes. Long-term data also confirm the absence of seasonality in births and conceptions. However, they show that mortality rates and risk of respiratory infections vary directly with rainfall. These relationships are probably causal and may be mediated through thermoregulatory stress.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1020366018187
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  • 4
    Electronic Resource
    Electronic Resource
    System controls on the aqueous distribution of mercury in the northern Florida Everglades (1998)
    Springer
    Biogeochemistry 40 (1998), S. 293-311 
    Details
    ISSN: 1573-515X
    Keywords: aqueous mercury species ; bioaccumulation ; methyl mercury ; marshes ; wetland systems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract The forms and partitioning of aqueous mercury species in the canals and marshes of the Northern Florida Everglades exhibit strong spatial and temporal variability. In canals feeding Water Conservation Area (WCA) 2A, unfiltered total Hg (HgTU) is less than 3 ng L-1 and relatively constant. In contrast, methyl mercury (MeHg) exhibited a strong seasonal pattern, with highest levels entering WCA-2A marshes during July. Stagnation and reduced flows also lead to particle enrichment of MeHg. In the marshes of WCA-2A, 2B and 3A, HgTU is usually 〈5 ng L-1 with no consistent north–south patterns. However, for individual dates, aqueous unfiltered MeHg (MeHgU) levels increase from north to south with generally lowest levels in the eutrophied regions of northern WCA-2A. A strong relationship between filtered Hg species and dissolved organic carbon (DOC), evident for rivers draining wetlands in Wisconsin, was not apparent in the Everglades, suggesting either differences in the binding sites of DOC between the two regions, or non-organic Hg complexation in the Everglades.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005928927272
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Trophic transfer of methyl mercury in the northern Florida Everglades (1998)
    Springer
    Biogeochemistry 40 (1998), S. 347-361 
    Details
    ISSN: 1573-515X
    Keywords: Everglades ; Hg transfer ; methyl mercury ; periphyton
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract There are spatial differences in methyl mercury (MeHg) concentrations in biota in Water Conservation Areas 2 and 3 in the Everglades, with higher concentrations generally found in the southern areas. Fish and hemipterans had the most MeHg on a wet weight basis, with levels exceeding 30 ng g-1. The magnitude of MeHg accumulation in biota varies seasonally and does not always appear to be associated with changes in water column concentration. This is exemplified by periphyton, the base of the foodweb in the Everglades, at a high nutrient sampling site. Although limited in scope, MeHg concentrations presented for biota provide insight into beginning to understand the dynamic nature of Hg transfer in the Everglades foodweb on a spatial and temporal basis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005918101773
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  • 6
    Electronic Resource
    Electronic Resource
    Diel variability of mercury phase and species distributions in the Florida Everglades (1998)
    Springer
    Biogeochemistry 40 (1998), S. 311-325 
    Details
    ISSN: 1573-515X
    Keywords: diel variability ; Everglades ; mercury cycling ; methyl mercury ; photochemical processes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract Preliminary studies of mercury (Hg) cycling in the Everglades revealed that dissolved gaseous mercury (DGM), total mercury (HgT), and reactive mercury (HgR) show reproducible, diel trends. Peak water-column DGM concentrations were observed on or about noon, with a 3 to 7 fold increase over night-time concentrations. Production of DGM appears to cease during dark periods, with nearly constant water column concentrations that were at or near saturation with respect to the overlying air. A simple mass balance shows that the flux of Hg to the atmosphere from diel DGM production and evasion represents about 10% of the annual input from atmospheric deposition. Production of DGM is likely the result of an indirect photolysis reaction that involves the production of reductive species and/or reduction by electron transfer. Diel variability in HgT and HgR appears to be controlled by two factors: inputs from rainfall and photolytic sorption/desorption processes. A possible mechanism involves photolysis of chromophores on the surface of a solid substrate (e.g., the periphyton mat) giving rise to destabilization of sorbed mercury and net desorption during daylight. At night, the sorption reactions predominate and the water-column HgT decreases. Methylmercury (MeHg) also showed diel trends in concentration but were not clearly linked to the solar cycle or rainfall at the study site.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005938607225
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    Paper (German National Licenses)
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