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  • Arylsulfatase A  (1)
  • Desert  (1)
  • Optimal foraging  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Spatial organization of a desert rodent community: food addition and species removal (1987)
    Springer
    Oecologia 72 (1987), S. 77-82 
    Details
    ISSN: 1432-1939
    Keywords: Desert ; Rodent community ; Food addition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary From 1977 through 1983 we conducted experiments on a desert rodent community where supplemental seeds were added or certain rodent species and ants were removed from 0.25-ha fenced plots in a Chihuahuan Desert site in southeastern Arizona, USA. In this paper we examine the patterns of microhabitat use relative to vegetative cover by 11 rodent species. The results show that: i) removal of the largest seed-eating species, Dipodomys spectabilis, produced the most pervasive and dramatic shifts in microhabitat use by the remaining rodent species; ii) adding seeds or removing ants had little effect on the spatial use of microhabitats by rodents in this community; and iii) non-granivores were just as likely as granivores to shift microhabitat use when other granivores were removed. We believe these results indicate that both food and foraging microsites are limited but the relegation of subdominant species to lesspreferred microhabitats by the large Dipodomys spectabilis is the major factor underlying the spatial organization of this community. Results also demonstrate that strong interactions among species increase the probability that pathways of indirect interactions through intermediary species are important; these complex linkages may include species that overlap little in food preferences.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00385048
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Seed selection by dark-eyed juncos (Junco hyemalis): optimal foraging with nutrient constraints? (1987)
    Springer
    Oecologia 74 (1987), S. 106-111 
    Details
    ISSN: 1432-1939
    Keywords: Optimal foraging ; Nutrient constraints
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Observations of the foraging behavior of six captive dark-eyed juncos (Junco hyemalis) are used to test the assumptions and predictions of optimal diet choice models (Pyke et al. 1977) that include nutrients (Pulliam 1975). The birds sequentially encountered single seeds of niger thistle (Guizotia abyssinica) and of canary grass (Phalaris canariensis) on an artificial substrate in the laboratory. Niger thistle seeds were preferred by all birds although their profitability in terms of energy intake (J/s) was less than the profitability of canary grass seeds. Of four nutritional components used to calculate profitabilities (mg/s) lipid content was the only characteristic that could explain the junco's seed preference. As predicted by optimal diet theory the probability of consuming niger thistle seeds was independent of seed abundance. However, the consumption of 71–84% rather than 100% of the seeds encountered is not consistent with the prediction of all-or-nothing selection. Canary grass seeds were consumed at a constant rate (no./s) independent of the number of seeds encountered. This consumption pattern invalidates a model that assumes strict maximization. However, it is consistent with the assumption that canary grass seeds contain a nutrient which is required in minimum amounts to meet physiological demands (Pulliam 1975). These experiments emphasize the importance of incorporating nutrients into optimal foraging models and of combining seed preference studies with studies of the metabolic requirements of consumers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00377353
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    Mammalian arylsulfatases A and B: relative rates of hydrolysis of artificial substrates (1986)
    Springer
    Cellular and molecular life sciences 42 (1986), S. 150-151 
    Details
    ISSN: 1420-9071
    Keywords: Arylsulfatase A ; arylsulfatase B ; 4-methylumbelliferyl sulfate ; rodent ; bovine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Rodent and bovine arylsulfatase B hydrolyze 4-methylumbelliferyl sulfate (4MUS) 10- to 30-fold more efficiently than arylsulfatase A. Therefore, 4MUS grossly underestimates arylsulfatase A activity in the presence of excess arylsulfatase B.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01952440
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    Paper (German National Licenses)
    Fulltext
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