Browsing by Author "Labra, A"

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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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    Chemical exploratory behavior in the lizard Liolaemus bellii
    (2001) Labra, A; Beltrán, S; Niemeyer, HM
    An experimental study was carried out to determine whether self and conspecific chemical recognition occurs in Liolaemus bellii, a Tropidurid lizard from Central Chile. Experiments were performed during the autumn and the spring. Using the number of tongue flicks as an indicator of discrimination, it was found that L. bellii showed both self and conspecific chemical recognition. Lizards recognized their own territories, and conspecific chemical recognition showed seasonal changes. During autumn, lizards showed higher exploratory behavior (higher numbers of tongue flicks and motion time) than in spring, and female enclosures elicited in males higher numbers of tongue nicks. Similar results were previously found in other Liolaemus species from a different habitat The information available at present for Liolaemus suggests that recognition of own territory is more important than recognition of conspecifics, and the latter seems to be associated mainly to the reproductive season. Therefore, conspecific and self-chemical recognition seem to be independent of the habitat used by the species, although habitat could modulate the use of chemical signals.
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    Interplay between pregnancy and physiological thermoregulation in Liolaemus lizards
    (2002) Labra, A; Bozinovic, F
    In squamate reptiles the effects of pregnancy on physiological thermoregulation, such as thermal tolerances and rates of heat exchange, are practically unknown. This is remarkable since pregnancy involves changes in body vascularization and may consequently affect heat exchange. We studied the effects of pregnancy on physiological thermoregulation,in four oviparous Liolaemus species from central Chile. Results indicated that pregnancy did not affect most of the variables measured. In two species, however, pregnant females had slower heating rates than non-pregnant individuals, suggesting a capacity to control the egg thermal environment. On the other hand, in contrast to other small lizards, in Liolaemus heating, but not cooling, rates may have an adaptive value as a thermoregulatory mechanism. Cooling rates and thermal minimal tolerances seem to evolve less readily.
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    Intraspecific variation in antipredator responses of three species of lizards (Liolaemus)
    (1999) Labra, A; Leonard, R
    Although humans are commonly used as a surrogate predator to assess the antipredator behavior of lizards, little is known about the effects that life associated with humans may have on the escape behavior of lizards. Here we examine the effects that coexistence with humans may have on the antipredator mechanisms in three species of Liolaemus (Tropiduridae). For each species we compared two populations exposed to different human densities, to test the null hypothesis that there is no interpopulational variation in the response to an approaching human in the field. Also it was determined whether coexistence with humans would affect the behavioral and physiological antipredator responses to a model of a natural predator in the laboratory. Lizard populations that were exposed to a high human density allowed a closer proximity of humans in the field, and decreased their rate of movement and breathing intensity in response to the presentation of a predator model in laboratory experiments. We discuss the effects humans may have upon the lizards antipredator behavior toward humans and natural predators.
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    Sources of pheromones in the lizard Liolaemus tenuis
    (2002) Labra, A; Escobar, CA; Ar, A; Niemeyer, HM
    Experimental tests were conducted with the lizard Liolaemus tenuis (Tropiduridae), to determine the potential sources of pheromones used in its chemical communication, centered in the phenomenon of self-recognition. During the post-reproductive season, feces of both sexes and secretions of precloacal pores (present only in males) were tested. Stimuli were presented to lizards spread on rocks, and the number of tongue-flicks (TF) to the rocks was used as a bioassay to determine pheromone recognition. Feces contained pheromones involved in self-recognition, since lizards showed less TF confronted to rocks with suspensions of their own feces than with suspensions of feces of conspecifics or with water (control). In order to assess the chemical nature of self-recognition pheromones, feces were submitted to a sequential extraction with three solvents of increasing polarity, thereby obtaining three feces fractions. There were no differences in TF towards rocks with different fractions with own feces. Additionally, lizards showed similar TF to rocks with fractions of own and conspecific feces, suggesting that the separation procedure broke up a complex stimulus into parts that were not active individually as pheromones. Finally, males did not discriminate between precloacal secretions from themselves and from another male. It is possible that these secretions convey information relevant to or detectable by females only.