Browsing by Author "MARQUET, PA"

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    BODY-SIZE, POPULATION-DENSITY, AND THE ENERGETIC EQUIVALENCE RULE
    (1995) MARQUET, PA; NAVARRETE, SA; CASTILLA, JC
    1. We critically evaluated the Energetic Equivalence Rule (EER) with regard to its underlying theoretical framework, its dependence of a particular relationship between population density and body size, and the way it is calculated.
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    COMPARATIVE ECOLOGY OF DARWIN FOX (PSEUDALOPEX-FULVIPES) IN MAINLAND AND ISLAND SETTINGS OF SOUTHERN CHILE
    (1990) JIMENEZ, JE; MARQUET, PA; MEDEL, RG; JAKSIC, FM
    Using comparable techniques we studied the abundance, habitat use, and diet of Darwin's fox (Pseudalopex fulvipes), as well as prey availability in two constrasting settings of southern Chile: on the mainland in the Nahuelbuta ranges, and in Chiloe Island. This fox lives in sympatry with its congener P. griseus in Nahuelbuta, but is the sole fox on Chiloe Island. We estimated that Darwin's fox is about twice as abundant in Chiloe than on the mainland. The structure of the habitat where Darwin's fox was found was remarkably similar between the two study sites despite floristic differences. Its diet, however, was markedly dissimilar, with mainland foxes preying extensively on mammals and reptiles and little on insects, and island foxes preying primarily on insects and amphibians, and little on mammals. The low consumption of mammals in Chiloe may be attributed to the low densities reached by that prey on the island as compared to Nahuelbuta (estimated at about double the insular density). Fruit consumption in Chiloe was almost three times higher than in Nahuelbuta, suggesting a lower energy diet for insular foxes. We also report behavioural observations on Darwin's fox provided by knowledgeable sources.
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    ECOLOGICAL ASPECTS OF THERMOREGULATION AT HIGH-ALTITUDES - THE CASE OF ANDEAN-LIOLAEMUS LIZARDS IN NORTHERN CHILE
    (1989) MARQUET, PA; ORTIZ, JC; BOZINOVIC, F; JAKSIC, FM
    We document activity field temperatures, daily activity patterns, and extent of thermoregulation in four species of Liolaemus lizards inhabiting at high altitude (above 3500 m) in the Andes of northern Chile. These four species similar activity field temperature (Tb near 29.degree.C) despite their being distributed at different altitudinal belts. However, conspicuous differences exist between higher-altitude (L. alticolor and L. jamesi) and lower-altitude (L. islugensis and L. ornatus) lizards regarding extent of thermoregulation and activity period. Some differences in morphology, behavior, and patterns of microhabitat occupancy are also apparent among these four species and are seemingly related to the thermal environment to which they are subjected. In comparison to eight low-altitude Liolaemus species in central Chile (Tb near 35.degree.C) the four high-altitude species in northern Chile have lower activity field temperature. The latter is apparently due to the constraints imposed by the harsh Andean thermal environment, a hypothesis supported by the fact that high-altitude Liolaemus lizards under laboratory conditions demonstrated body temperatures that exceed by 5.degree.C or more, those recorded in the field.
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    ENERGETICS AND TORPOR IN THE ATACAMA DESERT-DWELLING RODENT PHYLLOTIS-DARWINI RUPESTRIS
    (1991) BOZINOVIC, F; MARQUET, PA
    The energetics of the sigmodontine rodent Phyllotis darwini rupestris, inhabiting the Pacific coastal desert of northern Chile was studied. To determine torpor states, we measured rates of oxygen consumption at different ambient temperatures, with and without food. The combination of its low basal metabolic rate coupled with its capability to enter torpor under food restriction, may allow this species to inhabit variable and unpredictable environments.
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    MICROHABITAT SHIFTS OF LIZARDS UNDER DIFFERENT CONTEXTS OF SYMPATRY - A CASE-STUDY WITH SOUTH-AMERICAN LIOLAEMUS
    (1988) MEDEL, RG; MARQUET, PA; JAKSIC, FM
    The Iguanid lizard Liolaemus tenuis is shown to be a rock and trunk dweller (apparently preferring perches between 0-30 cm height) in a central Chilean locality where it coexists with a single ground-dwelling congener. In its southern distributional ranges L. tenuis is sympatric with another tree-dweller, L. pictus. Habitat shift is demonstrated in this latter case by L. tenuis concentrating on tree trunks, and at modal heights 30-60 cm. Liolaemus pictus occupies lower (apparently more favorable) perches, actively interferring with its congener.
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    NATURAL-HISTORY OF MICROCAVIA-NIATA IN THE HIGH ANDEAN ZONE OF NORTHERN CHILE
    (1993) MARQUET, PA; CONTRERAS, LC; SILVA, S; TORRESMURA, JC; BOZINOVIC, F
    We document the first record of Microcavia niata in the high Andes of northern Chile near the border of Bolivia. This species is restricted to bog habitats where it principally feeds on grasses and aquatic plants. Its basal metabolic rate was 0.689 +/- 0.1 ml O2 g-1 h-1. Two colonies were studied, each possessing 15 and 17 individuals, and characterized by female-biased sex ratios. Individuals reacted aggressively against the intrusion of non-colony members and elicited alarm calls under risk of predation.
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    NICHE RELATIONSHIPS BETWEEN 2 SYMPATRIC LIOLAEMUS LIZARDS IN A FLUCTUATING ENVIRONMENT - THE LEAN VERSUS FEAST SCENARIO
    (1989) NUNEZ, H; MARQUET, PA; MEDEL, RG; JAKSIC, FM
    Liolaemus fuscus and L. lemniscatus are two similarly-sized, completely sympatric species of central Chile. In some localities they are also syntopic, sharing the same microhabitat (rocks). We studied the microhabitat, time, and food use of these two species throughout one year, computing standard niche metrics. Between-species similarities on these three niche dimensions were very high at all times of the year (mean = 82% for all three microhabitat, time, and food overlaps), slightly decreasing during winter. The "feast" seasons of plentiful food, when dietary overlaps reached 90 and 99% (spring and summer, respectively) were associated with the two species overlapping broadly in microhabitat (77 and 81%, for spring and summer, respectively) and activity time (92 and 91%, respectively). "Lean" times were associated with decreased overlap in both diet (59 and 81% for fall and winter, respectively) and activity time (87 and 58%, respectively), but not in microhabitat (71 and 97%, respectively). Our data provide limited support for the view that interspecific niche relationships in fluctuating environments may be understood within the "lean" versus "feast" times scenario.
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    SCALING POPULATION-DENSITY TO BODY SIZE IN ROCKY INTERTIDAL COMMUNITIES
    (1990) MARQUET, PA; NAVARRETE, SA; CASTILLA, JC
    Interspecific comparisons of animal population density to body size has been the subject of active research in the last decade, especially for terrestrial animals when considering particular taxa or taxonomic assemblages. Studies of rocky intertidal communities showed that animal population density scales with body size to the -0.77 power. This relation held within local communities representing a broad array of animal taxa and was not affected by a dramatic alteration in the network of between-species interactions, as revealed by two long-term human exclusion experiments.