Browsing by Author "Hayes, Loren D."

Now showing 1 - 11 of 11
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    Burrow limitations and group living in the communally rearing rodent, Octodon degus
    (ALLIANCE COMMUNICATIONS GROUP DIVISION ALLEN PRESS, 2011) Ebensperger, Luis A.; Chesh, Adrian S.; Castro, Rodrigo A.; Ortiz Tolhuysen, Liliana; Quirici, Veronica; Burger, Joseph Robert; Sobrero, Raul; Hayes, Loren D.
    Group living is thought to evolve whenever individuals attain a net fitness advantage due to reduced predation risk or enhanced foraging efficiency, but also when individuals are forced to remain in groups, which often occurs during high-density conditions due to limitations of critical resources for independent breeding. The influence of ecological limitations on sociality has been studied little in species in which reproduction is more evenly shared among group members. Previous studies in the caviomorph rodent Octodon degus (a New World hystricognath) revealed no evidence that group living confers an advantage and suggest that burrow limitations influence formation of social groups. Our objective was to examine the relevance of ecological limitations on sociality in these rodents. Our 4-year study revealed no association between degu density and use of burrow systems. The frequency with which burrow systems were used by degus was not related to the quality of these structures; only in 1 of the 4 years did the frequency of burrow use decrease with decreasing abundance of food. Neither the number of females per group nor total group size (related measures of degu sociality) changed with yearly density of degus. Although the number of males within social groups was lower in 2008, this variation was not related clearly to varying density. The percentage of females in social groups that bred was close to 99% and did not change across years of varying density. Our results suggest that sociality in degus is not the consequence of burrow limitations during breeding. Whether habitat limitations contribute to variation in vertebrate social systems is discussed.
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    Fitness consequences of group living in the degu Octodon degus, a plural breeder rodent with communal care
    (2009) Hayes, Loren D.; Castro Bustamante, Rodrigo Alfredo; Ebensperger Pesce, Luis Alberto
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    Long-term field studies on rodents
    (2017) Hayes, Loren D.; Ebensperger Pesce, Luis Alberto; Kelt, Douglas A.; Pillay, Neville; Viblanc, Vincent A.; Schradin, Carsten; Meserve, Peter L.
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    Male group members are costly to plurally breeding Octodon degus females
    (2019) Hayes, Loren D.; Correa Kaempfe, Loreto Alejandra; Abades T., Sebastián R.; Gao, Cuilan L.; Ebensperger Pesce, Luis Alberto
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    Octodon degus kin and social structure
    (2016) Davis, Garrett T.; Vasquez, Rodrigo A.; Poulin, Elie; Oda, Esteban; Bazan Leon, Enrique A.; Ebensperger Pesce, Luis Alberto; Hayes, Loren D.
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    Postnatal development of the degu (Octodon degus) endocrine stress response is affected by maternal care
    (2016) Bauer, Carolyn M.; Ebensperger Pesce, Luis Alberto; León, Cecilia; Ramírez Estrada, Juan Carlos; Hayes, Loren D.; Romero. L. Michael
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    Reproductive correlates of social network variation in plurally breeding degus (Octodon degus)
    (ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD, 2013) Wey, Tina W.; Burger, Joseph R.; Ebensperger, Luis A.; Hayes, Loren D.
    Studying the causes and reproductive consequences of social variation can provide insight into the evolutionary basis of sociality. Individuals are expected to behave adaptively to maximize reproductive success, but reproductive outcomes can also depend on group structure. Degus (Octodon degus) are plurally breeding rodents, in which females allonurse indiscriminately. However, communal rearing does not appear to enhance female reproductive success, and larger group sizes are correlated with decreasing per capita pup production. To further investigate mechanisms underlying these patterns, we asked how differences in sex, season and average group reproductive success are related to degu association networks. We hypothesized that if reproductive differences mirror social relationships, then females (core group members) should show stronger and more stable associations than males, and female association strength should be strongest during lactation. We also hypothesized that, at the group level, social cohesion would increase reproductive output, while social conflict would decrease it. Females did have higher association strength and more preferred partners than males, but only during lactation, when overall female associations increased. Females also had more stable preferred social partnerships between seasons. A measure of social cohesion (average association strength) was not related to per capita pup production of female group members, but potential social conflict (heterogeneity of association strengths) was negatively related to per capita pup production of female group members. Our results highlight temporal and multilevel patterns of social structure that may reflect reproductive costs and benefits to females. (C) 2013 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.
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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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    Socioecological conditions predict degu social instability and provide limited cues to forecast subsequent breeding conditions
    (2021) Ebensperger Pesce, Luis Alberto; Abades, Sebastian; Riquelme De la Fuente, Juan Daniel; Correa, Loreto A.; Hayes, Loren D.
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