Browsing by Author "Soto-Gamboa, M"

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    Behavioral and physiological thermoregulation of Atacama desert-dwelling Liolaemus lizards
    (2001) Labra, A; Soto-Gamboa, M; Bozinovic, F
    The behavioral and physiological thermoregulation of three Atacama desert-dwelling Liolaemus lizards was studied and compared with previous data on Liolaemus from other ecosystems. The thermoregulatory mechanisms of the desert-dwelling species differed from those of the others, a consequence of differences in the habitat structure of the species. Desert species have higher critical thermal minima and, contrary to expectations, lower selected body temperatures than Liolaemus from Mediterranean environments. Results of the rate,, of thermal time constants suggest mechanisms to cope with the fast decrease of environmental temperature that occurs in the desert during the mid-afternoons. Finally, the manner in which selection of low body temperatures may allow survival in desert conditions is discussed. Keywords: thermal time constants, operative temperature, physiological and behavioral thermoregulation.
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    Fruit-disperser interaction in a mistletoe-bird system: a comparison of two mechanisms of fruits processing on seed germination
    (2002) Soto-Gamboa, M; Bozinovic, F
    We compared the effects of two mechanisms of fruit processing (defecation versus regurgitation) on seed germination and establishment in a mistletoe-bird system (Tristerix aphyllus - Mimus thenca). Despite regurgitation being more frequently observed than defecation, radicle of defecated seeds grew longer than that of regurgitated ones. In this fruit-seed disperser interaction, we demonstrate the importance of different mechanisms of fruit processing for cactus infection efficiency by the mistletoe.
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    Social cues and hormone levels in male Octodon degus (Rodentia)
    (2005) Soto-Gamboa, M; Villalón, M; Bozinovic, F
    Social interactions are important factors determining and regulating individual behaviors. Testosterone has been related to agonistic interactions, while glucocorticoids have been related to social stress, especially during interactions of dominance. We compared testosterone and cortisol concentrations in male degus (Octodon degus, Rodentia) under laboratory conditions without male social interactions, with data from wild males in nature. Under natural conditions, males should present higher levels of testosterone during the breeding season due to social interactions (Challenge Hypothesis). Alternatively, intense social instability could act as a stressing environment, raising glucocorticoids, which inhibit testosterone concentrations. Our results show a significant increase in agonistic interactions between males during the breeding season, and disappearance of non-agonistic male interactions during this period. Hormone levels in breeding season show nonsignificant differences between laboratory groups, but testosterone concentrations in field males were significantly higher than in laboratory males. Testosterone levels were similar among pre-breeding and breeding periods, but in field animals the concentration was similar to30% higher than in laboratory degus. In field animals, we found two different mating strategies: resident males, with territorial behavior, and transient males, displayed an opportunistic approach to females. Finally, cortisol presents a similar pattern in both laboratory and field animals; pre-breeding values of cortisol are higher than during the breeding season. This suggests that social interactions in O.degus activate a rise in testosterone, supporting the Challenge Hypothesis, and could be considered as partial support of the Social Stress Hypothesis. (C) 2004 Elsevier Inc. All rights reserved.