Browsing by Author "Leon, Cecilia"

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    Fecal cortisol levels predict breeding but not survival of females in the short-lived rodent, Octodon degus
    (2013) Ebensperger, Luis A.; Tapia, Diego; Ramirez-Estrada, Juan; Leon, Cecilia; Soto-Gamboa, Mauricio; Hayes, Loren D.
    The cort-adaptation hypothesis indicates that an association between glucocorticoid (cort) levels and fitness may vary with the extent to which reproduction or breeding effort is a major determinant of cort levels. Support for a context dependent association between cort and fitness comes mostly from relatively long-lived, bird species. We tested the hypothesis that there are gender and context (life-history) specific cort-fitness relationships in degus, a short-lived and generally semelparous social rodent. In particular, we used demographical records on a natural population to estimate adult survival through seasons and years and linked that to records of baseline cort (based on fecal cortisol metabolites). We found no evidence for a direct relationship between baseline cort and adult survival across seasons, and this lack of association was recorded irrespective of sex and life history stage. Yet, cort levels during early lactation predicted the probability that females produce a second litter during the same breeding season, supporting a connection between baseline cort levels and breeding effort. Overall, the differential effects of cort on survival and breeding supported that the extent of cort-fitness relationships depends on the fitness component examined. (C) 2013 Published by Elsevier Inc.
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    Nest and space use in a highland population of the southern mountain cavy (Microcavia australis)
    (2006) Ebensperger, Luis A.; Taraborelli, Paula; Giannoni, Stella M.; Hurtado, Maria Jos; Leon, Cecilia; Bozinovic, Francisco
    We examined the spatial and social structure of a high-altitude population of the scarcely known southern mountain cavy (Microcavia australis) in Argentina. We used radiotelemetry techniques to monitor nest use at night and daily home ranges and examine whether southern mountain cavies form nesting associations that are socially cohesive groups. We further timed our observations to breeding time of our study population (September-November) to assess opportunities for communal breeding. The nighttime telemetry of 24 radiotagged cavies revealed 7 nesting associations (i.e., communal nesting). These included 1-4 breeding females and I or 2 breeding males. Nesting associations were stable in terms of identity of individual members and in the location of putative nest sites. Most associations used a single nest site, but some shared 2 or 3. We noted that all nest sites were located under dominant shrubs, but use of nest sites was unrelated to variation in shrub cover. Nest sites with more burrow entrances were more frequently used by radiocollared cavies. During the day, home ranges of cavies overlapped more with ranges of nest mates than with those of non-nest mates, implying that nesting groups were socially cohesive units. This study confirmed that southern mountain cavies are communally nesting, and, because communal nesting occurs during breeding time, our findings support the idea that cavies engage in communal care of young.
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    Sociality, glucocorticoids and direct fitness in the communally rearing rodent, Octodon degus
    (ACADEMIC PRESS INC ELSEVIER SCIENCE, 2011) Ebensperger, Luis A.; Ramirez Estrada, Juan; Leon, Cecilia; Castro, Rodrigo A.; Ortiz Tolhuysen, Liliana; Sobrero, Raul; Quirici, Veronica; Burger, Joseph Robert; Soto Gamboa, Mauricio; Hayes, Loren D.
    While ecological causes of sociality (or group living) have been identified, proximate mechanisms remain less clear. Recently, close connections between sociality, glucocorticoid hormones (cart) and fitness have been hypothesized. In particular, cort levels would reflect a balance between fitness benefits and costs of group living, and therefore baseline coil levels would vary with sociality in a way opposite to the covariation between sociality and fitness. However, since reproductive effort may become a major determinant of stress responses (i.e., the cart-adaptation hypothesis), cort levels might also be expected to vary with sociality in a way similar to the covariation between sociality and fitness. We tested these expectations during three years in a natural population of the communally rearing degu, Octodon degus. During each year we quantified group membership, measured fecal cortisol metabolites (a proxy of baseline cort levels under natural conditions), and estimated direct fitness. We recorded that direct fitness decreases with group size in these animals. Secondly, neither group size nor the number of females (two proxies of sociality) influenced mean (or coefficient of variation, CV) baseline cortisol levels of adult females. In contrast, cortisol increased with per capita number of offspring produced and offspring surviving to breeding age during two out of three years examined. Together, our results imply that variation in glucocorticoid hormones is more linked to reproductive challenge than to the costs of group living. Most generally, our study provided independent support to the cort-adaptation hypothesis, according to which reproductive effort is a major determinant, yet temporally variable, influence on cart-fitness covariation. (C) 2011 Elsevier Inc. All rights reserved.
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    Socially unstable conditions experienced during development prime female Octodon degus to shape the phenotype of their own offspring
    (2021) Ebensperger, Luis A.; Gomez, Celeste; Aspillaga-Cid, Antonia; Leon, Cecilia; Ramirez-Estrada, Juan; Correa, Loreto A.; Vera, Daniela C.; Abades, Sebastian; Hayes, Loren D.
    Because residents and immigrants from group living species may experience fitness costs associated with permanent changes in group membership, we examined the hypothesis that females experiencing socially unstable or socially stable conditions during development compensate these costs by shaping the phenotype of their own offspring differently. Groups of adult females experiencing either socially stable or unstable conditions in the early social environment were assigned to either socially stable or unstable conditions in the social environment as adults. We quantified affiliative and agonistic interactions among the females during pregnancy and lactation of the focal female, maternal and allomaternal care, hypothalamic-anterior pituitary-adrenal axis (HPA) acute stress response, and early offspring growth. Social instability during breeding enhanced agonistic interactions among adult females, and offspring that experienced socially unstable conditions exhibited enhanced offspring care, regardless of adult environments. Neither social behavior, offspring care, acute stress physiology, nor early growth was influenced by early or adult social stability conditions. These findings imply that socially unstable conditions prime developing females to shape the phenotype of their offspring to prevent negative effects of socially unstable environments.